Aexq0071-02 (1) Bob Cat

Maintenance Manual
THDC / THDCP - 954 / 955 / 974 /

975
DEATH OR SERIOUS INJURY MAY RESULT FROM IMPROPER
OPERATION OF THIS MACHINE
D OPERATOR MUST BE TRAINED AND KNOWLEDGEABLE OF

THE OPERATOR’S GUIDE, SAFETY MANUAL, AND OSHA
STANDARD SECTION 29 CFR 1910.178 FOR POWERED
INDUSTRIAL TRUCKS.
D CAPACITY IS WITH MAST IN VERTICAL POSITION AND
LOAD RETRACTED.
D CAPACITY GREATLY DECREASES WITH TILTING, HIGH
LOAD LIFTING, ACCELERATION, BRAKING, SHARP
TURNING, HIGH WIND VELOCITY, AND POOR YARD
CONDITIONS.
D TILT (MAST AND LOAD OUT) ONLY WHEN LOAD IS OVER
A STACK.
D VISIBILITY MAY BE IMPAIRED BY STRUCTURAL
DESIGN. (ALWAYS LOOK IN DIRECTION OF TRAVEL;
DO NOT RELY ON MIRRORS.)
D DO NOT OPERATE WITH BYSTANDERS PRESENT.
D ALWAYS TRAVEL WITH LOAD IN LOWEST POSSIBLE
POSITION THAT ALLOWS GOOD VISIBILITY.
D ALWAYS WEAR SEAT BELT WHILE MACHINE IS IN
OPERATION.
D DO NOT ATTEMPT TO JUMP FROM MACHINE IN EVENT OF
TIP OVER. REMAIN SEATED WITH SEAT BELT FASTENED.
TAYLOR MACHINE WORKS, INC.

650 NORTH CHURCH AVENUE
LOUISVILLE, MISSISSIPPI 39339-2017 3374 715
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 7/05)

Observe The Following Precautions For Maximum Safety Of Machine Operation
1. Only trained and responsible operators shall be permitted to handle loads with this truck.
2. Operate the truck from the operator’s seat only. Do not allow riders.
3. Test hydraulic controls for proper response before using the machine.
4. Know your load. Do not attempt to lift or transport loads in excess of rated capacity.
5. When the load obstructs the view, operate the truck in the reverse range.
6. Do not stand or work under an elevated load.
7. Transport the load low and tilted back.
8. Avoid sudden stops with a load.
9. Center the load to evenly distribute the weight.
10. Back down a ramp in excess of 10 percent when loaded.
11. Do not move the truck until the air system reaches recommended pressure. Air pressure is
required for the service brakes.
12. Have defects repaired immediately. Do not operate a truck with damaged or defective sys-
tems.
13. When leaving truck, lifting mechanism shall be fully lowered, controls shall be neutralized, pow-
er shut off, parking brake set, and key removed. Block wheels if on incline.
LIMITED WARRANTY
Products manufactured by Taylor Machine Works, Inc. (“Taylor”) and sold are warranted by Taylor to be free from
defects in material and workmanship, under normal use and service, when Taylor products are operated at or
below rated capacity* in accordance with operating instructions.
This warranty is limited to repair or replacement, (as Taylor may elect, and at an establishment authorized by
Taylor) of such parts as shall appear to Taylor upon inspection to have been defective in material or
workmanship.
This warranty period shall begin on the delivery date of the product to the Purchaser and end on whichever
occurs first of the warranty period, twelve (12) months or two thousand (2000) hours. During this period, Taylor
will provide genuine Taylor parts, labor, and travel time to replace or repair any part furnished by Taylor and found
to be defective in material and workmanship.** If a defect in material and workmanship is found during the twelve
(12) months and/or two thousand (2000) hours whichever occurs first of the warranty period, Taylor will replace
lubricating oil, filters, antifreeze, and other service items made unusable by the defect. Only genuine Taylor parts
provided by Taylor’s Sudden Service, Inc. will be used during the warranty period.
THE FOLLOWING ITEMS ARE NOT COVERED BY THIS WARRANTY:

1. Normal maintenance services and parts or supplies used therein including, without limitation, en-
gine tune-up, wheel alignment, brake and linkage adjustment, lubrication services, tightening and
adjusting such as bolts, screws, hoses, fittings, etc., replacement of fuses, bulbs, filters, tune-up
parts, fluids and brake and clutch linings, glass; shop supplies such as rags, oil dry, hand soaps,
degreasers, cleaning solutions including brake clean, etc.; and adjustments which are a part of
the required or recommended predelivery inspection and periodic inspections in accordance with
Operator’s Manual. Electrical components including wiring will be excluded after the first six (6)
months or one thousand (1000) hours whichever occurs first.
2. Leaks due to o-ring failures and fittings after one hundred (100) hours of operation.
3. Normal deterioration of appearance due to use and exposure; or conditions resulting from mis-
use, negligence, or accident.
4. Any product on which any of the required or recommended periodic inspections or services have
not been made.
5. Any parts or accessories, installed on the product which were not manufactured or installed by
Taylor whether or not such parts or accessories were selected, recommended or installed by Tay-
lor (including without limitation, engines, tires, batteries, air conditioners, air dryers, etc.). Such
parts or accessories shall be covered by the warranties given by the manufacturers thereof and
any claim thereof shall be made to such manufacturers.
6. Loss of time, inconvenience, loss of equipment use, other consequential damages or other mat-
ters not specifically included.
Taylor parts and assemblies which are furnished and installed under this warranty are themselves within
the coverage of the machine warranty and are covered only for the duration of the original machine
warranty period.
NOTE: All International warranty parts shipments are F.O.B. point of debarkation, duties, tariffs, or local
taxes excluded.
This warranty is expressly in lieu of any other warranties, expressed or implied, including any warranty of
merchantability or fitness for a particular purpose.
Replacement parts are warranted for ninety (90) days to be free from defects in material or workmanship. Parts
only, no labor.
Taylor Machine Works, Inc. does not authorize any person to create (for Taylor) any other obligation or liability in
connection with Taylor products.
*For example, a machine rated capacity at any stipulated load center is the rated lift capacity at less than
load center. That is, a machine rated at 20,000 pounds at 24-inch load center connotes 20,000 pounds
is the maximum lift capacity even though the load center may be less than 24-inches. Subjecting Taylor
products to conditions or loads exceeding those stipulated is justification for immediate cancellation of
warranty for products involved.
**Travel reimbursement will be limited to six (6) hours maximum paid per claim, or to the nearest Taylor
Machine Works’ dealer location in the assigned territory in which the truck is based.
TAYLOR MACHINE WORKS, INC.

650 North Church Avenue
Louisville, Mississippi 39339
(662) 773-3421 / Fax 662-773-9146
TMW-057-4 (12/04)
Introduction
This manual is to be used as a guide for lubrication and maintenance as well as general equipment care.
A separate section is provided to discuss each major component or system. This method of presenting
the maintenance instructions enables Taylor Machine Works, Inc. to assemble a maintenance manual with
explicit instructions on the exact equipment installed on the machine.
No single rule in the booklet can be followed to the exclusion of others. Each rule must be considered in
light of the other rules, the knowledge and training of the man (operator), the limitations of the machine,
and the workplace environment.
Warnings and cautions are included to reduce the probability of personal injury, when performing mainte-
nance procedures which if improperly performed could be potentially hazardous. Failure to comply with
these warnings and cautions can result in serious injury and possible death.
All circumstances and conditions under which service will be performed cannot be anticipated. Do not
perform any service if you are unsure that it can be done safely. Contact your Taylor Dealer or Taylor
Machine Works, Inc. if you have questions about the proper service techniques.

Operating this powered industrial truck when it is in need of repair can result in
death or serious injury to the operator or other personnel or cause severe property damage.
Machine checks must be performed daily:
1. before the machine is placed in service,
2. by qualified, trained, and skilled personnel who have proper tools and knowledge, and
3. in accordance with the Operator’s Guide, Maintenance Manual and Safety Check booklet.
OperatorsGuide
Maintenance Manual
Ê
! .
! .
Regularly Scheduled maintenance, lubrication, and safety inspections will help ensure a safe and
productive work life for the machine and the operator(s).

Do not operate the truck if it is in need of repair. Remove the ignition key and
attach a “Lock-out” tag.

Do not attempt to perform maintenance procedures unless you have been
thoroughly trained and you have the proper tools.
THDC-954
THDC - 955
/ THDCP (6/99)
- 954 / 955 / 974 / 975 (Rev. 06/03) Intro

Use only genuine Taylor replacement parts. Lesser quality parts may fail,
resulting in property damage, personal injury or death.
Maintenance and / or service personnel who find it necessary to operate this machine, even for a short
period of time, must fully understand all operational literature including:
• OSHA operating rules found in 29 CFR 1910.178; Appendix A in Safety Check
• ANSI B56.1 rules for operating a powered industrial truck; Appendix B in Safety Check
• The Operator’s Guide for the machine
• The manufacturer’s Safety Booklet
• The manufacturer’s Safety Video
• The manufacturer’s Service Bulletins
• The content and meaning of all machine decals

Know how to avoid slip and fall accidents such as those described in the Slip and
Fall Accidents Section of Safety Check.
Intro THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Safety
Safety First
Important Safety Instructions 1. Use of hoisting devices not capable of

Observe these rules. They are recognized as supporting the weight of the component being
practices that reduce the risk of injury to yourself lifted.
and others, or damage to the container handling 2. Improper attachment of slings to heavy
truck or load. components being hoisted.
This manual contains maintenance and service 3. Use of inadequate or rotten timbers for sup-
procedures for filling, lubricating, removing, repair- port or improper alignment of supporting
ing, and installing various components comprising material.
a container handling truck. Because of the size 4. Failure to securely block the wheels, when dis-
and weight of the container handling truck, and connecting or removing components that hold
high pressures in some of the components and the container handling truck stationary under
systems, improperly performing service on the normal conditions.
truck can be dangerous. 5. Failure to read and understand the safety pre-
Warnings and cautions are included to reduce the cautions in this manual.
probability of personal injury, when performing
maintenance procedures which if improperly

Know how to avoid accidents
performed could be potentially hazardous. Failure
such as those described in the Maintenance /
to comply with these warnings and cautions can
Service Accidents Section of Safety Check:
result in serious injury and possible death.
No single rule in the booklet can be followed to Some Maintenance / Servicing Accidents
the exclusion of others. Each rule must be con- Listed below:
sidered in light of the other rules, the knowledge 1. Improperly refueling the truck.
and training of the man (operator / maintenance), 2. Improperly checking for hydraulic leaks or
the limitations of the machine, and the workplace diesel fuel leaks.
environment. 3. Improperly checking the engine cooling
Report all mechanical problems to mechanics and system.
supervisors. 4. Improperly checking battery fluid levels or
Proper Training: “jump” starting engines.
5. Putting air in a multi-piece tire and rim assem-
Taylor Machine Works, Inc. publishes Safety bly without proper tools and training.
Check, TMW-072 a booklet citing some safety
precautions to observe during lift truck operation. 6. Attempting to service a multi-piece tire and rim
One copy is shipped with each lift truck; additional assembly without proper tools and training.
copies are available at a nominal fee from the 7. Using an improperly suited chain while
authorized Taylor dealer from which the equip- performing maintenance.
ment was initially purchased. 8. Using the container handling truck hydraulic
Minimum Required Personnel Safety Equipment system as a substitute for a fixed stand.
1. Hard Hat 9. Relying on jacks or hoists to support heavy
loads.
2. Safety Shoes
10. Operating a truck that is damaged or in need
3. Safety Glasses of repair.
4. Heavy Gloves 11. Climbing on the mast of a forklift, on the top of
5. Hearing Protection the cab, or other high places on the container
6. Reflective Clothing handling truck.
Failure to follow the safety precautions outlined in 12. Operating a container handling truck which
this manual can create a dangerous situation. has been modified without the manufacturer’s
Some of the common ways this can occur are as approval. This includes the attachment, coun-
follows: terweight, tires, etc.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) Safety-1

13. Lifting people with a forklift not properly equipment. Under no circumstances should
equipped for elevating personnel. any attempt be made to disconnect or in any
14. Improperly using chains. way render any of these devices inoperable. If
you discover that any safety device is mal-
15. Improperly blocking and supporting mast, car-
functioning, Do Not operate the truck; notify
riage, or attachment before repairing truck.
appropriate maintenance personnel immedi-
Maintenance / Service Personnel: ately.
1. Keep the truck clean, free of oil, grease and
fuel.

Use only genuine Taylor
2. Steam clean / wash the truck prior to perform- replacement parts. Lesser quality parts may
ing maintenance. Wear anti-slip footwear fail, resulting in property damage, personal
when performing maintenance procedures. injury or death.
3. Use OSHA approved ladders and other proper
cleaning accessories to access hard to reach
maintenance places.
Keep all hydraulic com-
ponents in good repair.
4. Keep gratings free of ice, dirt and gravel.
5. Regularly inspect and replace anti-slip mastic
on the vehicle as needed.
Relieve pressure on the
6. Ensure all safety decals are in place on the hydraulic system before repairing or adjusting
or disconnecting.
vehicle.

Remove all rings, watches,
Wear proper hand and eye
chains, other jewelry, and all loose clothing protection when searching for leaks. Use wood
before working around moving parts! or cardboard instead of hands.

Do not operate the vehicle or
Under no circumstances,
attempt to perform maintenance on the vehicle without prior written approval from Taylor
while under the influence of alcohol, drugs, or Machine Works, Inc. Engineering Department,
any other medications or substances that slow should the container handling truck be modi-
reflexes, alter safe judgement, or cause drows- fied, i.e. adding of additional counterweights.
iness. As per OSHA 29 CFR1910.178 (a) (4).
Container Handling Truck Lock-out / Tag-out:

Never park the container The engine should be locked-out / tagged-out to
handling truck on an incline. Always park the prevent it from being inadvertently started before
container handling truck on a level surface; performing maintenance or repairs. The battery
otherwise, the lift truck could possibly roll should be locked-out / tagged-out to prevent acci-
resulting in possible injury to personnel or dental activation of the starter and possible start-
damage to the truck or other property. ing the engine. Refer to Lock-Out / Tag-Out Pro-
cedure in the back of this section for the
procedures to be followed to perform lock-out /

Maintenance and service
tag-out.
personnel should never operate this lift truck
unless they are thoroughly familiar with Safety
Check, TMW-072 and the Operator’s Guide for
Turn the engine off and
this lift truck. remove the ignition key before entering the tire
pivot area to prevent death or serious injury
from pivoting tires.

Electrical, mechanical, and
hydraulic safety devices have been installed
on this container handling truck to help protect
Deflate tires before removing
against personal injury and / or damage to (the tires). Always remove the valve core and
Safety-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

exhaust all air from a single tire and both tires Traveling:
of a dual assembly prior to removing any rim Start, stop, change direction and travel smoothly.
components or wheel components such as Slow down while turning.
nuts and rim clamps. Run a piece of wire
through the valve stem to make sure the valve Obstructions And Clearances:
stem is not damaged or plugged and all air is Watch end clearances and overhead obstructions.
exhausted.

Do not release the parking

Serious falls and injuries can brake or attempt to move the container han-
result from improper mounting or dismounting dling truck if the air pressure gauge indicates
of the container handling truck. that the air pressure is below 100 psi.
Mounting and Dismounting:

1. Face the container handling truck when get-
Make sure all ground person-
ting on or off the truck. nel know the rules and responsibilities set by
your employer. Make sure they know what you
2. One hand and two feet or two hands and one are going to do and be sure they are clear of
foot must be in contact with the truck at all the area before you move the container han-
times (3 point contact). dling truck.
3. Use handrails and other grab points.

Cameras are not substitutes

Do not start the engine if the for looking in the direction of and keeping a
ignition switch, or engine control panel has clear view of the path of travel. Never use
been locked-out / tagged-out by maintenance them as substitutes, Always look in the path of
personnel. Doing so can result in personal travel.
injury and / or damage to the equipment. If in
doubt, contact the maintenance supervisor.

Total reliance on electrical
aids can be dangerous. The responsibility for

If maintenance requires run- safe operation of the container handling truck
ning the engine indoors, ensure the room has shall remain with the operator who shall
adequate flow-through ventilation! ensure that all warning and instructions pro-
vided are fully understood and observed.

Never operate the container
handling truck without proper instruction.
Do not operate the container
Ignorance of operational characteristics and handling truck until both forward and reverse
limitations can lead to equipment damage, travel paths are clear. Do not operate the truck
personal injury, or death. with bystanders present.

Do not move the container
handling truck without the seat belt properly handling truck until the surrounding area has
and securely fastened. been checked and is clear of personnel and
obstructions.

Operating instructions, warn-
ings, and caution labels are placed on the con-
Always look in the direction
tainer handling truck to alert personnel to dan- of travel and keep a clear view of the path of
gers and to advise personnel of proper travel; slow down and sound the horn at cross
operating procedures (of the lift truck). Do not aisles and other locations where vision may be
remove or obscure any warning, caution, dan- obscured.
ger, or instructional sign or label.

This equipment is not electri-
Stacks of containers or mate-
cally insulated. Contact with electricity can rials can cause “blind spots” for the operator.
cause severe injury or death. Electrocution It is essential, for safe operation, that the
can occur without direct contact. Do not oper- ground crew stay clear of “blind spots” and
ate this container handling truck in areas with stay within sight of the operator at all times.
energized power lines or a power supply. Do not allow anyone to walk in the travel aisle-
Check local, state and federal safety codes for ways.
proper clearance. Use a groundman to ensure
that there is proper clearance.

Do not move or lift container
until all four twistlocks are fully locked (green

Do not allow anyone on the container light illuminated). The container
container handling truck during operation. could fall from the attachment causing death
or serious injury to ground personnel or physi-
cal damage to the container, container han-

Do not move the container dling truck or other yard equipment.
handling truck onto a surface or area that has
not been approved for container handling
truck operation. The container handling truck
Do not lift a loaded container
is heavy and could possibly break through an that exceeds the rated capacity of the contain-
insufficient surface and cause damage to the er handling truck. Failure to do so, may result
truck or injury to personnel. in death, personal injury or damage to the con-
tainer handling truck.

handling truck over potholes and debris. Clear
Do not handle unstable
the yard of obstructions. loaded containers.
If the load shifts in the container, stop the truck

Avoid sudden starts and immediately, lower the container and adjust the
stops. side shift until load weight is centered and proper-
ly held. If the load shift is too great for adjustment
with side shift, lower the container and rearrange

Serious falls or injuries can the load before attempting to move the container.
result from riding on the container handling
truck! Do not ride on the container handling
truck.
Never move containers over
personnel or vehicles.
Handling Loads:

Do not back away from a

If any abnormal operating rack or stack without complete release of the
condition occurs while operating the container container. Failure to do so, may result in death
handling truck, move the truck to a safe park- or serious bodily injury and property damage
ing area, if possible; when safe to do so, shut caused by dropping a container on the truck, a
down the truck and notify the appropriate bystander or on the ground.
maintenance personnel.

Position the container before

Do not allow anyone near the traveling to eliminate interference with visibili-
container handling truck - certainly not walk- ty in the direction of travel.
ing or standing under or beside the container
or lifting mechanism.

Use care when traveling with
or without a container.

Lock-Out / Tag-Out Procedure

Never leave the container Purpose. This procedure establishes the mini-
handling truck with a container suspended. mum requirements for lock-out / tag-out of energy
The load could inadvertently lower and cause sources that could cause injury to personnel. All
serious injury or death. employees shall comply with the procedure.
Responsibility. The responsibility for seeing that

Be exact in load placement. this procedure is followed is binding upon all
Make sure the load will not tilt, fall or slide out employees. All employees shall be instructed in
of position when released. Personal injury or the safety significance of the lock-out / tag-out
equipment damage can result from unstable procedure by (designated individual). Each new
placement of loads. or transferred affected employee shall be
instructed by (designated individuals) in the pur-
pose and use of the lock-out / tag-out procedure.

Do not unlatch a container
until you, the operator, have determined that it Preparation for Lock-Out / Tag-Out. Employees
is safe to do so. Never unlatch a container authorized to perform lockout / tagout shall be cer-
that is not positioned securely; the container tain as to which switch, valve, or other energy iso-
could shift or fall. lating devices apply to the equipment being
locked out / tagged out. More than one energy
source (electrical, mechanical, or others) may be

Do not back away from a involved. Any questionable identification of
rack or stack with a container until it is clear of sources shall be cleared by the employees with
the container below it. Failure to do so, may their supervisors. Before lock-out / tag-out com-
result in death or serious bodily injury and mences, job authorization should be obtained.
property damage caused by dropping a con- Sequence of Lock-Out / Tag-Out Procedure
tainer on the truck, a bystander or on the
ground. 1. Notify all affected employees that a lock-out /
tag-out is required and the reason therefor.
Battery Safety: 2. If the equipment is operating, shut it down by
the normal stopping procedure.

Lighted smoking materials, 3. Operate the switch, valve, or other energy iso-
flames, arcs, or sparks may result in battery lating device so that the energy source(s)
explosion. (electrical, mechanical, hydraulic, etc.) is dis-
connected or isolated from the equipment.
1. Keep all metal tools away from battery termi-
Stored energy, such as that in capacitors,
nals.
springs, elevated crane members, rotating fly-
2. Batteries contain sulfuric acid which will burn wheels, hydraulic systems, and air, gas,
skin on contact; wear rubber gloves and eye steam, or water pressure, etc. must also be
protection when working with batteries. dissipated or restrained by methods such as
3. Flush eyes or wash skin with water and seek grounding, repositioning, blocking, bleeding-
medical attention immediately in case of down, etc.
contact. 4. Lock-out / tag-out the energy isolating devices
4. When jump starting: with an assigned individual lock / tag.
a. Do not lean over the battery while making 5. After ensuring that no personnel are exposed
connection. and as a check on having disconnected the
b. First, connect the positive (+) terminal of energy sources, operate the push button or
the booster battery to the positive (+) other normal operating controls to make cer-
terminal of the discharged battery. tain the equipment will not operate.
c. Then, connect the negative (-) terminal of
the booster battery to the engine or body
Return operating controls to
ground (-). Never Cross Polarity of
Terminals. neutral after the test.
d. Disconnect cables in exact reverse order.

6. The equipment is now locked out / tagged out.
Restoring Equipment to Service
1. When the job is complete and equipment is
ready for testing or normal service, check the
equipment area to see that no one is exposed.
2. When equipment is all clear, remove all locks /
tags. The energy isolating devices may be
operated to restore energy to equipment.
Procedure Involving More Than One Person.
In the preceding steps, if more than one individual
is required to lock-out / tag-out equipment, each
shall place his own personal lock / tag on the
energy isolating device(s). One designated indi-
vidual of a work crew or a supervisor, with the
knowledge of the crew, may lock-out / tag-out
equipment for the whole crew. In such cases, it
shall be the responsibility of the individual to carry
out all steps of the lock-out / tag-out procedure
and inform the crew when it is safe to work on the
equipment. Additionally, the designated individual
shall not remove a crew lock / tag until it has been
verified that all individuals are clear.
Rules for Using Lock-Out / Tag-Out Procedure.
All equipment shall be locked out / tagged out to
protect against accidental or inadvertent operation
when such operation could cause injury to person-
nel. Do not attempt to operate any switch, valve,
or other energy isolating device bearing a lock /
tag.

Major Components Locations
ATTACHMENT MAST
(Section 29) (Section 27)
LIFT CYLINDER
(Section 22)
TILT CYLINDER
(Section 22)
CAB
(Section 20)
STEER AXLE
(Section 13)
FUEL TANK
(Section 2)
HYDRAULIC TANK RADIATOR

(Section 22) (Section 5)
ENGINE
(Section 1)
TRANSMISSION
(Section 9)
DRIVE AXLE
(Section 14) DRIVE SHAFT
(Section 11)
NOTE: All circuit drawings illustrate the components in de-energized states. Circuit drawings and
illustrations are drawn in the position of the operator facing forward, looking toward the mast
assembly.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

1-2 (Rev. 11/94)
Contents
Maintenance Manual
Section
Introduction
Engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Fuel System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Air Intake System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Exhaust System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Transmission Oil Cooler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A
Transmission Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9C
Drive Shaft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Steer Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Drive Axle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Brake Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Wet Disc Brakes Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C
Air Dryer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15D
Steering System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Tires and Wheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chassis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Cab . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Air Conditioning System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20A
Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20H
Hydraulic System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Cab Tilt System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22D
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22E
Mast Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Container Attachment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Appendices
Section 1
Engine
OIL
DIPSTICK
OIL
FILLER
CAP
OIL
FILTER
ELEMENT
WASHER
DRAIN PLUG
Illustration 1-1. Cummins QSM11-C330 Engine Service Points

Introduction. This engine is pressure lubricated, on the oil dipstick to ensure the engine has the
generating 330 horsepower at 2100 governed rpm proper amount of oil for operation.
and delivering 1170 ft-lbs of peak torque at 1400
Changing the Oil and Filter Element (Illustration
rpm. Oil pressure is supplied by a gear-type lubri-
1-1). The engine lubricating oil should be
cating oil pump and controlled by a pressure regu-
changed monthly or every 250 hours, whichever
lator. The filter bypass valve ensures that a sup-
comes first. The oil filter should be replaced each
ply of oil, in the event the filter becomes plugged,
time the engine oil is changed. Refer to the Fuel
is present. One full flow oil filter is incorporated in
and Lubricant Specifications chart in the back
the lubricating system to provide maximum
of this manual for the proper grade of oil to use.
cleansing and filtration of the engine lubricating
oil. If additional engine information is needed,
refer to the engine operation and maintenance

manual supplied with the truck. S Park machine on a level surface, apply
Checking the Lubricating Oil (Illustration 1-1). parking brake, block wheels and Lock Out &
The engine lubricating oil should be checked daily Tag Out while servicing machine.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-1

S Avoid touching exhaust components while 8. Remove the oil fill cap and fill crankcase with
changing the oil for severe burns could oil to the FULL mark on the oil dipstick (see
occur. Illustration 1-1).
S Some state and federal agencies in the 9. Start the engine and allow to idle. Visually
United States have determined that used check the drain plug and oil filter for leaks.
engine oil can be carcinogenic and can
cause reproductive toxicity. Avoid inhala- 10. Shut down the engine and wait approximately
tion of vapors, ingestion and prolonged 5 minutes for the oil to drain back into the oil
contact with used engine oil. pan. When the engine has cooled, recheck
the oil level and add oil as necessary to bring
the oil level to the FULL mark on the oil dip-
stick.
S Dispose of oil and filter in accordance with
federal and local regulations.
S Do not use a strap wrench to tighten the oil
filter. Mechanical over-tightening may
distort the threads or damage the filter
gasket.
S Never operate the engine with the oil level
below the ADD mark or above the FULL mark
on the oil dipstick.
S Do not use excessive amounts of starting
fluid when starting the engine. The use of
too much starting fluid will cause engine
damage.
1. Operate the engine until the water tempera-
ture reaches 140°F and then shut off the
engine.
2. Place a suitable container under the drain plug Illustration 1-2. Drive Belt Inspection
of the oil pan. Remove the drain plug and
washer to drain the oil. Replace washer if Drive Belts (Illustration 1-2). Visually inspect the
damaged. drive belts daily. Check the belt for intersecting
3. When the oil has completely drained, reinstall cracks. Transverse cracks (across the belt width)
the washer and drain plug. Apply a torque of are acceptable. Longitudinal cracks (direction of
65 ft-lbs of torque to tighten the drain plug. belt length) that intersect with transverse cracks
are not acceptable. Replace the belt if belt is
4. Unscrew the spin-off type oil filter (see frayed or has pieces of material missing. Adjust
Illustration 1-1). It should be possible to drive belts that have a glazed or shiny surface
unscrew the oil filter by hand; however, a band which indicates belt slippage. Correctly installed
type filter wrench may be used if necessary. and tensioned belts will show even pulley and belt
Discard the used oil filter. wear. After installation of a new belt, check the
5. Clean the area on the filter base that will con- tension and adjust if necessary.
tact the gasket on the new oil filter. Belt damage can be caused by:
6. Fill the new filter with clean engine oil S Incorrect tension
before installation. S Incorrect size or length
7. Apply a light film of engine oil on the gasket of S Pulley misalignment
the new filter. Screw the new filter onto the S Incorrect installation
filter base until the gasket comes in contact
with the filter base and then tighten filter 1/2 to S Severe operating environment
3/4 turn by hand only. S Oil or grease on the belts
1-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

ered used if it has been in operation for 10 min-
utes or longer. If the used belt tension is less than
the minimum tension value, tighten the belt to the
maximum tension value. To obtain the proper belt
tension value, use an appropriate belt tension
gauge. Perform the following procedures to
adjust the tension of the belt.
Do not adjust belt tension to

the maximum value with the adjusting screw.
Belt tension can increase when the locknut is
tightened and cause reduced belt and bearing
life.
1. Loosen the idler pulley shaft locknut.
2. Adjust the belt to the correct tension by turning
the adjusting screw clockwise until the proper
belt tension is obtained (see Caution above).
3. Tighten the idler pulley shaft locknut to a
torque value of 140 ft-lbs (190 N⋅m).
4. Check the belt tension again to make sure the
belt is adjusted to the correct value.
Alternator Drive Belt Tension (Illustration 1-4).
The tension of the alternator drive belt should be
60 - 120 ft-lbs (270 - 530 N⋅m) for a used belt and
Illustration 1-3. Fan Drive Belt
150 ft-lbs (670 N⋅m) for a new belt. A belt is con-
sidered used if it has been in operation for 10 min-
ADJUSTMENT utes or longer. If the used belt tension is less than
LINK LOCKING the minimum tension value, tighten the belt to the
CAPSCREW maximum tension value. To obtain the proper belt
ADJUSTING
SCREW LOCKNUT tension value, use an appropriate belt tension
gauge. Perform the following procedures to
adjust the tension of the belt:
1. Loosen the adjusting screw locknut.
2. Loosen the adjustment link locking capscrew.
3. Loosen the pivot capscrew and nut.
4. Adjust the belt to the correct tension by turning
the adjusting screw clockwise until the proper
belt tension is obtained.
5. Tighten the adjusting screw locknut against
PIVOT CAPSCREW the retainer.
AND NUT
6. Tighten the adjustment link locking capscrew
Illustration 1-4. Alternator Drive Belt to a torque value of 60 ft-lbs (80 N⋅m).
Fan Drive Belt Tension (Illustration 1-3). The 7. Tighten the pivot capscrew and nut to a torque
tension of the fan drive belt should be 200 - 240 value of 35 ft-lbs (47 N⋅m).
ft-lbs (890 - 1070 N⋅m) for a used belt and 300 Engine Cleaning. The engine must be steam
ft-lbs (1330 N⋅m) for a new belt. A belt is consid- cleaned every 6 months or 1500 hours, whichever
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-3

comes first. If steam is not available, use a sol- tion position (first click).
vent to wash the engine. When cleaning the
2. Cycle the accelerator pedal through its full
engine, protect all electrical components, open-
range of travel three times.
ings and wiring from the full force of the cleaner
spray nozzle. 3. Turn the ignition switch to the Off position for
30 seconds.

When using a steam cleaner, Diagnostic Lights (Illustration 1-5). The diagnos-
wear protective clothing and safety glasses or tic lights, located on the right side of the dash, are
a face shield. Hot steam will cause serious used to alert the operator of engine related prob-
personal injury. lems. At initial power up, all 3 lights will be illumi-
nated for 2 seconds. After 2 seconds, the red
Checking Engine Mounting Bolts. The engine light will turn off. After 2.5 seconds, the yellow
mounting bolts should be checked for the light will turn off. After 3 seconds from power up,
appropriate torque every 6 months or 1500 hours, the blue light will turn off. Each light’s function is
whichever comes first. The torque value of the listed as follows:
engine mounting bolts is 380 ft-lbs. Inspect the 1. Blue Light. This light will begin to flash at
rubber mounts for deterioration and age harden- approximately 230 hours, indicating routine
ing. Replace any broken or lost bolts and dam- maintenance is forthcoming. This light illumi-
aged rubber mounts. nates at approximately 250 hours when rou-
tine maintenance is required. To reset this
Cummins QSM11-C330 Engine General Infor- light, perform the following procedures to reset
mation the blue light:
Oil Pressure (normal) 28 - 35 psi a. Toggle the diagnostic switch (located
inside the dash on the right side) to the ON
Oil Capacity position.
39.2 quarts
(includes filter change)
b. Turn the ignition key to its accessory posi-
High RPMs (no load) 2250 rpm tion (first click).
Low RPMs 750 rpm c. Allow all the diagnostic lights to complete
the flash sequences prior to starting proce-
NOTES: dure 4.
S Setting high rpms under no load conditions to d. Fully depress the accelerator pedal and
2250 rpm ensures that the engine will have hold for more than 3 seconds.
2100 rpms under a loaded condition.
e. Fully depress the accelerator pedal twice
S Some special applications may use engine (each time less than 1 second).
speed settings that are different from the stan-
dards shown. The proper settings are perma- f. Fully depress the accelerator pedal and
nently stamped on a metal tag affixed to the hold for more than 3 seconds.
engine.
NOTE: Procedures d. through f. must be com-
Calibration Of Electronic Accelerator Pedal To pleted within 30 seconds.
ECM Of Engine. The Cummins QSM11 engine
uses an electronic accelerator to control engine g. The blue light will flash three quick flashes
speed. Each time the accelerator pedal is signifying that the ECM has responded to
changed, disconnected and the ignition switch is the reset command.
turned on, or ECM (Electronic Control Module) is
h. Toggle the diagnostic switch to the OFF
changed out, the accelerator pedal must be cali-
position.
brated to the ECM. Calibration procedures are as
follows: i. Turn the ignition switch to the OFF posi-
tion. Allow the ignition switch to remain off
1. Apply the parking brake, place the shifter in for a minimum of 30 seconds before turn-
neutral, and turn the ignition switch to the Igni-
1-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

ing the ignition switch back on to confirm that will come on. Only active fault codes can be
that the blue light has been reset. viewed by use of the diagnostic lights. To view
inactive fault codes, a laptop computer equipped
2. Yellow Light (System Fault). This light illumi-
with Cummins Insite software is required.
nates during a non-fatal system error. The
engine can still be run, but the fault should be To view active fault codes, perform the following:
corrected as soon as possible.
1. Turn off the engine.
NOTE: In the diagnostic mode, the yellow light 2. Toggle the diagnostic switch (located inside
will flash after the red light completes the three- the dash on the right side) to the ON position.
digit fault code.
3. Turn the ignition key to its accessory position
3. Red Light (Engine Shutting Down). This light (first click). If no active fault codes are record-
illuminates when the engine needs to be shut ed, the yellow light (System Fault) and red
off before permanent damage occurs to the light (Engine Shutting Down) will illuminate
engine. Should the red light illuminate while and stay on. If active fault codes are record-
operating, the fault can be engine disabling ed, the yellow light and red light will illuminate
after approximately 32 seconds. Should the momentarily, and then the red light will begin
engine shut down due to the severity of the to flash the three-digit code of the recorded
fault, it can be restarted and will run for fault(s).
approximately 32 seconds. The engine will 4. The fault code will flash in the following
run for approximately 32 seconds each time it sequence:
is restarted. There are no limits on the num-
ber of times the engine may be restarted. a. First, the yellow light will flash beginning
the sequence. There will be a short 1 or 2
NOTES: second pause after which the red light will
S The engine should be shut off as soon as it flash the first, second, and third digits of
can be shut off safely. The engine should not the recorded fault code. There will be a 1
be run until the fault is corrected. or 2 second pause between each number
of the code. When all three digits of the
S This light is also used to flash out the fault fault code have flashed, the yellow light will
code number in the diagnostic mode. illuminate again and repeat the sequence
until the fault is cleared or the Diagnostic
switch is toggled to the OFF position.
BLUE YELLOW RED
LIGHT LIGHT LIGHT Example:
Fault Code 432
4 flashes, pause
3 flashes, pause
2 flashes
b. If multiple fault codes have been stored,
the first fault code must be cleared before
the second fault code can be displayed.
Fault Code Information. All fault codes identified
in bold print on the preceding fault code informa-
tion chart deal with engine and transmission
Illustration 1-5. Diagnostic Lights protection systems external to the Cummins
QSM11 engine. Fault code #151 can be caused
Diagnostic Fault Codes (Illustration 1-5). If the by both engine and external components.
red light (Engine Shutting Down) or yellow light Contact Taylor Machine Works Sudden Service
(System Fault) light comes on when the engine is Department for additional assistance if needed.
running, it means a fault code has been recorded.
The light will remain on as long as the fault exists.
The severity of the fault will determine the light
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-5

QSM11 Fault Code Information
Fault Code - Light Failure Description Failure Results
111 - Red Error internal to the ECM related to memory The engine will not start.
hardware failures or internal ECM voltage sup-
ply circuits.
115 - Red No engine speed signal detected at both The engine will die and will not start.
engine position sensor circuits.
121 - Yellow No engine speed signal detected from one of None on performance.
the engine position sensor circuits.
122 - Yellow High voltage detected on the intake manifold Derate in power output of the engine.
pressure circuit.
123 - Yellow Low voltage detected on the intake manifold Derate in power output of the engine.
pressure circuit.
131 - Red High voltage detected at the throttle position Severe derate (power and speed). Limp home
signal circuit. power only.
132 - Red Low voltage detected at the throttle position Severe derate (power and speed). Limp home
signal circuit. power only.
133 - Red High voltage detected at the remote throttle None on performance if remote throttle is not
position signal circuit. used.
134 - Red Low voltage detected at the remote throttle None on performance if remote throttle is not
position signal circuit. used.
135 - Yellow High voltage detected at the oil pressure cir- No engine protection for oil pressure.
cuit.
141 - Yellow Low voltage detected at the oil pressure cir- No engine protection for oil pressure.
cuit.
143 - Yellow Oil pressure signal indicates oil pressure is Progressive power and speed derate with
below the low oil pressure engine protection increasing time after alert. Engine will shut
limit. down 30 seconds after red light starts flashing.
144 - Yellow High voltage detected at the coolant tempera- Possible white smoke. Fan will stay on if con-
ture circuit. trolled by the electronic control module (ECM).
No engine protection for coolant temperature.
145 - Yellow Low voltage detected at the coolant tempera- Possible white smoke. Fan will stay on if con-
ture circuit. trolled by the electronic control module (ECM).
147 - Red A frequency of less than 100 Hz was detected Calibration dependent power and speed
at the frequency throttle signal pin of the derate.
actuator harness connector at the ECM.
148 - Red A frequency of more than 100 Hz was Calibration dependent power and speed
detected at the frequency throttle signal pin of derate.
the actuator harness connector at the ECM.
151 - Red Coolant temperature signal indicates coolant Progressive power derate with increasing time
temperature is above 104_C (220_F). after alert. Engine will shut down 30 seconds
after red light starts flashing.
153 - Yellow High voltage detected at the intake manifold Possible white smoke. Fan will stay on if con-
temperature circuit. trolled by the electronic control module (ECM).
154 - Yellow Low voltage detected at the intake manifold Possible white smoke. Fan will stay on if con-
temperature circuit. trolled by the electronic control module (ECM).
1-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

155 - Red Intake manifold temperature signal indicates Progressive power derate with increasing time
temperature is above 87.8_C (190_F). after alert. If Engine Protection Shutdown fea-
ture is enabled, engine will shut down 30 sec-
onds after red light starts flashing.
187 - Yellow Low voltage detected on the ECM voltage The engine will run derated. No engine
supply line to some sensors (VSEN2 supply). protection for oil pressure and coolant level.
211 - None Additional OEM or Vehicle diagnostic codes None on engine performance.
have been logged. Check other ECM’s for
diagnostic codes.
212 - Yellow High voltage detected at the oil temperature No engine protection for oil temperature.
circuit.
213 - Yellow Low voltage detected at the oil temperature No engine protection for oil temperature.
circuit.
214 - Red Oil temperature signal indicates oil tempera- Progressive power derate with increasing time
ture is above 123.9_C (255_F). after alert. If Engine Protection Shutdown fea-
ture is enabled, engine will shut down 30 sec-
onds after red light starts flashing.
219 - Blue Low oil level was detected in the Centinelt None on performance. Centinelt is deacti-
makeup oil tank. vated.
221 - Yellow High voltage detected at the ambient air pres- Derate in power output of the engine.
sure circuit.
222 - Yellow Low voltage detected at the ambient air pres- Derate in power output of the engine.
sure circuit.
223 - Yellow Incorrect voltage detected at the Centinelt None on performance. Centinelt is deactiva-
actuator circuit by the ECM. ted.
227 - Yellow High voltage detected on the ECM voltage The engine will run derated. No engine
supply line to some sensors (VSEN2 supply). protection for oil pressure and coolant level.
234 - Red Engine speed signal indicates engine speed is Fuel shutoff valve closes until engine speed
greater than 2730 rpm. falls to 2184 rpm.
235 - Red Coolant level signal indicates coolant level is Engine will shut down 30 seconds after red
below the normal range. light starts flashing. Add coolant as required.
237 - Yellow Duty cycle of the throttle input signal to the pri- All engines (primary and secondary) are shut
mary or secondary engine for multiple unit down with increasing time after alert if hard-
synchronization is less than 3% or more than coupled. Only secondary engines are shut
97%. down with increasing time after alert if soft-
coupled.
241 - Yellow The ECM lost the vehicle speed signal. Engine speed limited to Maximum Engine
Speed without Vehicle Speed Sensor parame-
ter value Cruise Control, Gear-Down Protec-
tion and Road Speed Governor will not work
(automotive only).
242 - Yellow Invalid or inappropriate vehicle speed signal Engine speed limited to Maximum Engine
detected. Signal indicates an intermittent con- Speed without Vehicle Speed Sensor parame-
nection or VSS tampering. ter value Cruise Control, Gear-Down Protec-
tion and Road Speed Governor will not work
(automotive only).
245 - Yellow Less than 6 VDC detected at fan clutch circuit Then fan may stay on at all times.
when on. Indicates an excessive current draw
from the ECM or faulty ECM output circuit.
254 - Red Less than 6 VDC detected at FSO circuit when The ECM turns off the FSO supply voltage.
on. Indicates an excessive current draw from The engine will shut down.
the ECM or a faulty ECM output circuit.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-7

255 - Yellow Externally supplied voltage detected going to None on performance. Fuel shutoff valve
the fuel shutoff solenoid supply circuit. stays open.
285 - Yellow The ECM expected information from a multi- At least one multiplexed device will not oper-
plexed device but did not receive it soon ate properly.
enough or did not receive it at all.
286 - Yellow The ECM expected information from a multi- At least one multiplexed device will not oper-
plexed device but only received a portion of ate properly.
the necessary information.
287 - Red The OEM vehicle electronic control unit The engine will only idle.
(VECU) detected a fault with its throttle pedal.
288 - Red The OEM vehicle electronic control unit The engine will not respond to the remote
(VECU) detected a fault with its remote throttle.
throttle.
293 - Yellow High voltage detected at the OEM temperature No engine protection for OEM temperature.
sensor signal pin of the 31-pin OEM connec-
tor.
294 - Yellow Low voltage detected at the OEM temperature No engine protection for OEM temperature.
tor.
295 - Yellow An error in the ambient air pressure sensor The engine is derated to no air setting.
signal was detected by the ECM.
297 - Yellow High voltage detected at the OEM pressure No engine protection for OEM pressure.
tor.
298 - Yellow Transmission’s temperature exceeds 245_F. Engine will shut down 30 seconds after the red
light begins flashing.
299 - Yellow Engine shutdown by device other than key- No action taken by the ECM.
switch before proper engine cool down result-
ing in filtered load factor above maximum shut-
down threshold.
311 - Yellow Current detected at No. 1 injector when the Current to the injector is shut off.
voltage is turned off.
319 - Blue Real time clock lost power. None on performance. Data in the ECM will
not have accurate time and date information.
voltage is turned on.
322 - Yellow No current detected at No. 1 injector when the Current to the injector is shut off.
1-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

341 - Yellow Severe loss of data from the ECM. Possible no noticeable performance effects
OR engine dying OR hard starting. Fault infor-
mation, trip information, and maintenance
monitor data may be inaccurate.
343 - Yellow Internal ECM error. Possible none on performance or severe
derate.
349 - Yellow A frequency greater than calibrated threshold Calibration dependent power and speed
was detected at the tailshaft governor signal of derate.
the 31-pin OEM connector.
352 - Yellow Low voltage detected on the ECM voltage The engine is derated to no air setting.
supply line to some sensors (VSEN1 supply).
386 - Yellow High voltage detected on the ECM voltage The engine is derated to no air setting.
supply line to some sensors (VSEN1 supply).
387 - Yellow High voltage detected on the ECM voltage The engine will only idle.
supply line to the throttle(s) (VTP supply).
415 - Red Oil pressure signal indicates oil pressure is Progressive power derate with increasing time
below the very low oil pressure engine protec- from alert. Engine will shut down 30 seconds
tion limit. after red light starts flashing.
418 - Blue Water has been detected in the fuel filter. Possible white smoke, loss of power, or hard
starting.
419 - Yellow An error in the intake manifold pressure sen- The engine is derated to no air setting.
sor signal was detected by the ECM.
422 - Yellow Voltage detected simultaneously on both the Engine will shut down 30 seconds after red
coolant level high and low signal circuits OR light starts flashing. Disconnected or loose
no voltage detected on both circuits. plug at coolant sensor, defective coolant sen-
sor, or loose or broken wire between sensor
and ECM.
426 - None Communication between the ECM and the None on performance. J1939 devices may
J1939 data link has been lost. not operate.
428 - Yellow High voltage detected at water-in-fuel sensor. None on performance.
429 - Yellow Low voltage detected at water-in-fuel sensor. None on performance.
431 - Yellow Voltage detected simultaneously on both the None on performance.
idle validation off-idle and on-idle circuits.
432 - Red Voltage detected at idle validation on-idle cir- The engine will only idle.
cuit when voltage at throttle position circuit
indicates the pedal is not at idle OR voltage
detected at idle validation off-idle circuit when
voltage at throttle position circuit indicates the
pedal is at idle.
433 - Yellow Voltage signal at intake manifold pressure cir- Derate to no air setting.
cuit indicates high intake manifold pressure
but other engine characteristics indicate intake
manifold pressure must be low.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-9

434 - Yellow Supply voltage to the ECM fell below 6.2 VDC Possible no noticeable performance effects
for a fraction of a second OR the ECM was not OR possibility of engine dying OR hard star-
allowed to power down correctly (retain battery ing. Fault information, trip information, and
voltage for 30 seconds after key off). maintenance monitor data may be inaccurate.
435 - Yellow An error in the oil pressure sensor signal was None on performance. No engine protection
detected by the ECM. for oil pressure.
441 - Yellow Battery voltage is below the normal operating Possible no noticeable performance effects
level. OR possibility of rough idle.
442 - Yellow Battery voltage is above the normal operating None on performance.
level.
443 - Yellow Low voltage detected on the ECM voltage The engine will only idle.
supply line to the throttle(s) (VTP supply).
489 - Yellow Auxiliary speed frequency on input pin indi- The engine will only idle.
cated that the frequency is below a calibration
dependent threshold.
527 - Yellow Less than 17.0 VDC detected at the dual out- No action taken by the ECM.
put A signal pin of the 31-pin OEM connector.
put B signal pin of the 31-pin OEM connector.
put B signal pin at the ECM.
551 - Yellow No voltage detected simultaneously on both The engine will only idle.
the idle validation off-idle and on-idle circuits.
581 - Yellow High voltage detected at the fuel inlet restric- Fuel inlet restriction monitor deactivated.
tion sensor signal pin.
582 - Yellow Low voltage detected at the fuel inlet restric- Fuel inlet restriction monitor deactivated.
tion sensor signal pin.
583 - Yellow Restriction has been detected at the fuel pump Fuel inlet restriction monitor warning is set.
inlet.
596 - Yellow High battery voltage detected by the battery Yellow light will be illuminated until high battery
voltage monitor feature. voltage condition is corrected.
597 - Yellow ICONt has restarted the engine 3 times within Yellow light will be illuminated until low battery
3 hours due to low battery voltage (automotive voltage condition is corrected. The ECM may
only) OR low battery voltage detected by the increase idle speed and deactivate idle decre-
battery voltage monitor feature. ment switch if idle speedup is enabled. The
engine will run continuously if ICONt is active
(automotive only).
598 - Red Very low battery voltage detected by the bat- Red light will be illuminated until very low bat-
tery voltage monitor feature. tery voltage condition is corrected.
611 - None Engine shutdown by operator before proper No action taken by the ECM.
engine cool down resulting in filtered load fac-
tor above maximum shutdown threshold.
951 - None A power imbalance between cylinders was The engine may have rough idle or misfire.
detected by the ECM.
1-10 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Engine Troubleshooting (Cummins QSM11-C330)
(Illustration 1-6)
The following chart includes some of the problems 3. Has a similar trouble occurred before?
that an operator may encounter during the service 4. If the engine still runs, is it safe to continue
life of a Cummins diesel engine. Always check operation of the engine in an effort to diag-
the easiest and obvious things first, such as the nose the trouble?
master disconnect switch, the neutral start switch,
Check the items most easily and inexpensively
an empty fuel tank, closed fuel shut off, dead bat-
corrected before proceeding to the more difficult,
tery or corroded terminals. Study the problem
time consuming and expensive items. After a
thoroughly before starting to work on the engine.
malfunction has been corrected, locate and cor-
Ask yourself the following questions.
rect the cause of the trouble to prevent recurrence
1. What were the warning signs preceding the of the same trouble.
trouble?
2. Has the engine been subjected to recent
repair or maintenance?
Problem Cause Correction
1. Air compressor air 1. Intake air restriction to air compres- 1. Remove restriction.
pressure rises sor is excessive.
slowly 2. Air system leaks. 2. Check for air compressor gasket,
hoses, and fitting leaks. Check for
safety pressure valve leaks. Rat-
ing must be 135 psi.
3. Carbon buildup excessive in the air 3. Check valve or cylinder head for
discharge line. carbon buildup and remove.
4. Contact a Cummins Authorized
Repair Facility.
2. Air compressor 1. Air system leaks. 1. Block the truck’s wheels. Inspect
cycles frequently the air system for leaks with the
parking brakes applied and re-
leased. Check for leaks from the
air compressor gaskets and the air
system hoses, fittings, and valves.
2. Carbon buildup is excessive in the 2. Check for air discharge line, check
air discharge line, check valve, or valve, and cylinder head for carbon
cylinder head. buildup. Replace the air compres-
sor discharge line if required.
3. Air compressor pumping time is 3. Replace the desiccant cartridge in
excessive. the air dryer (if equipped). Check
the air compressor duty cycle.
Repair Facility.
3. Air compressor 1. Carbon buildup excessive in the air 1. Refer to Correction 3. of Problem
noise is excessive discharge line. 1. of this troubleshooting chart.
continued
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-11

3. Air compressor 2. Ice buildup in the air system com- 2. Inspect air discharge line and
noise is excessive ponents. elbow fittings for ice. Remove ice.
(Continued) 3. Contact a Cummins Authorized
Repair Facility.
4. Air compressor 1. Air compressor pumping time 1. Check air compressor duty cycle.
pumping excess excessive.
lubricating oil into 2. Carbon buildup excessive in the air 2. Refer to Correction 3. of Problem
the air system discharge line. 1. of this troubleshooting chart.
Repair Facility.
5. Air compressor will 1. Air system leaks. 1. Refer to Correction 2. of Problem

not maintain ade- 1. of this troubleshooting chart.
quate air pressure 2. Contact a Cummins Authorized
(not pumping con- Repair Facility.
tinuously)
6. Air compressor will 1. Air system leaks. 1. Refer to Correction 2. of Problem

not stop pumping 1. of this troubleshooting chart.
2. Defective air governor. 2. Replace air governor.
Repair Facility.
7. Alternator not 1. Alternator belt is loose. 1. Check belt tension.

charging or insuffi- 2. Battery cable or connection is 2. Check battery cables and connec-
ciently charging loose, broken or corroded (exces- tions.
sive resistance).
3. Batteries failed. 3. Check battery conditions.
4. Alternator pulley is loose on shaft. 4. Tighten pulley.
Repair Facility.
8. Coolant loss - 1. Coolant level is high. 1. Check coolant level.

External 2. The 7 and 15 psi radiator caps 2. Install radiator caps onto desig-
were placed on wrong radiator filler nated filler neck (see Illustration
necks. 5-3).
3. Radiator cap is incorrect or 3. Replace with correct radiator cap
defective. (15 psi).
4. External engine leak. 4. Visually inspect the engine and
components for seal or gasket
leaks and repair.
continued 5. Radiator or cab heater is leaking. 5. Visually inspect the radiator,
1-12 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
8. Coolant loss - (continued) heater, hoses and con-

External nections for leaks and repair.
(Continued) 6. Engine is overheating. 6. Refer to Problems 9. and 10. of
this troubleshooting chart.
Repair Facility.
9. Coolant tempera- 1. Coolant level is low. 1. Inspect the engine and cooling sys-
ture above normal tem for external leaks. Repair as
(gradual overheat) required. Add coolant as required.
2. Charge air cooler fins, radiator fins, 2. Inspect the charge air cooler, air
or air conditioner condenser fins conditioner condenser, and radiator
are damaged or obstructed with fins. Clean or repair as required.
debris, insects, dirt, etc.
3. Radiator hoses are collapsed, 3. Inspect and repair radiator hoses.
restricted or leaking.
4. Fan drive belt or water pump belt is 4. Check belt tension and tighten if
loose. necessary.
5. Incorrect oil level. 5. Add or drain engine oil as required.
6. Cooling fan shroud is damaged. 6. Inspect shroud; repair or replace.
7. Radiator cap is incorrect or 7. Replace with correct radiator cap
defective. (15 psi).
8. Overconcentration of antifreeze 8. Use the correct antifreeze con-
and / or supplemental coolant addi- centration (refer to the engine op-
tives. eration and maintenance manual).
9. Defective water pump. 9. Replace water pump.
10. Defective thermostat. 10. Replace thermostat.
Repair Facility.
10. Coolant tempera- 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
ture above normal Information chart in this section.
(sudden overheat) 2. Coolant temperature sensor mal- 2. Check / clean sensor and cool-
function. ant passage.
3. Coolant level is low. 3. Inspect for external leaks on
engine and radiator, and make
repairs.
4. Radiator hoses are collapsed, 4. Inspect and repair radiator hoses.
restricted, or leaking.
5. Fan drive belt is broken. 5. Replace drive belt.
6. Charge air cooler fins, radiator fins, 6. Inspect the charge air cooler, air
or air conditioner condenser fins conditioner condenser, and radiator
continued are damaged or obstructed with fins. Clean or repair as required.
debris, insects, dirt, etc.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 1-13
10. Coolant tempera- 7. Radiator cap is incorrect or defec- 7. Replace with correct radiator cap
ture above normal tive. (15 psi).
(sudden overheat) 8. Defective water pump. 8. Replace water pump.
(Continued)
9. Defective thermostat. 9. Replace thermostat.
10. The 7 and 15 psi radiator caps 10. Install radiator caps onto desig-
were placed on wrong radiator filler nated filler neck (see Illustration
necks. 5-3).
Repair Facility.
11. Coolant tempera- 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
ture below normal Information chart in this section.
2. Coolant temperature sensor mal- 2. Check / clean sensor and cool-
function. ant passage.
3. Engine operating at low ambient 3.
temperature.
4. Temperature gauge malfunction. 4. Test the gauge and replace if nec-
essary.
5. Thermostat is incorrect or malfunc- 5. Check thermostat and replace if
tioning. necessary.
Repair Facility.
12. Engine accelera- 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
tion or response is Information chart in this section.
poor 2. Engine operating at low ambient 2.
temperature.
3. Air intake system or exhaust sys- 3. Check for loose or damaged piping
tem leaks. connections, and missing pipe
plugs. Check the turbocharger and
exhaust manifold mounting (Refer
to the Cummins Engine Operation
and Maintenance Manual.
4. Fuel grade is not correct or fuel 4. Operate the engine from a tank of
quality is poor. high-quality fuel (refer to the Fuel
and Lubricant Specifications in
the Appendices).
Repair Facility.
13. Engine deceler- 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
ates slowly Information chart in this section.
continued
1-14 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
13. Engine deceler- 2. Accelerator pedal is sticking. 2. Check for a sticking accelerator
ates slowly pedal.
(Continued) 3. Contact a Cummins Authorized
Repair Facility.
14. Engine difficult to 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
start or will not Information chart in this section.
start (no smoke 2. Low fuel tank level. 2. Add fuel.
from exhaust)
3. Exhaust system is leaking hot air 3. Check the exhaust plumbing for
into engine compartment. leaks or broken components.
4. Fuel shutoff valve closed. 4. Repair fuel shutdown solenoid.
5. Battery voltage supply to the elec- 5. Check the battery connections.
tronic control system is low, inter- Check the fuses and the un-
rupted, or open. switched battery supply circuit.
6. Fuel filter(s) are plugged. 6. Replace fuel filter(s).
7. Fuel connection is loose on suction 7. Tighten all fuel fittings and connec-
side of fuel pump. tions from fuel tank to fuel pump.
8. Starting motor rotation is incorrect. 8. Check direction of crankshaft rota-
tion. Replace starting motor if nec-
essary.
9. Engine cranking speed too slow. 9. Check engine cranking rpm. Refer
to Problem 26. of this troubleshoot-
ing chart.
10. Loose wire on master disconnect 10. Isolate and tighten wire.
switch.
Repair Facility.
15. Engine difficult to 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
start or will not Information chart in this section.
start (exhaust 2. Batteries have drained or are 2. Recharge or replace batteries.
smoke present) defective.
3. Fuel shutoff valve(s) is closed 3. Check the fuel shutoff valve and
(electronically controlled injection). circuit.
4. Fuse(s) malfunctioning. 4. Replace the fuse(s) in the OEM
interface harness.
6. Intake air or exhaust system is 6. Check intake air and exhaust sys-
restricted. tems for restrictions. Remove
restrictions.
7. Fuel grade is not correct or fuel 7. Operate the engine from a tank of
quality is poor. high-quality fuel (refer to the Fuel
and Lubricant Specifications in
the Appendices).
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 1-15
15. Engine difficult to 8. Engine cranking speed too slow. 8. Check engine cranking rpm. Refer
start or will not to Problem 26. of this troubleshoot-
start (exhaust ing chart.
smoke present) 9. Hydraulic pump is dead-headed. 9. De-energize hydraulic circuit.
(Continued)
10. Starting aid needed for cold weath- 10. Check / repair or replace cold start-
er or not working properly. ing aid if necessary.
Repair Facility.
16. Engine noise 1. Oil supply insufficient or oil pres- 1. Check oil level. Refer to Problem
excessive sure is low. 36. of this troubleshooting chart.
2. Lubricating oil is thin or diluted. 2. Refer to the Fuel and Lubricant
Specifications in the Appendices
for the proper type of oil to use.
Refer to Problem 34. of this trou-
bleshooting chart.
3. Coolant temperature is above 3. Refer to Problem 10. of this trou-
normal. bleshooting chart.
4. Loose motor mount. 4. Inspect and tighten motor mounts.
5. Fan belt is malfunctioning. 5.
a. Fan belt is too loose or too a. Check the tension and adjust if
tight. needed.
b. Fan belt is not in alignment. b. Check pulley alignment and
adjust is necessary.
6. Damaged vibration damper. 6. Check vibration damper and
replace if required.
7. Drive shaft is not in phase. 7. Reposition drive shaft.
Repair Facility.
17. Engine noise 1. Poor fuel quality. 1. Verify by operating from a tempo-
excessive (com- rary tank with good fuel. Clean
bustion knocks) and flush the fuel supply tanks,
and use the proper fuel (refer to
the Fuel and Lubricant Specifica-
tions in the Appendices).
2. Engine operating at low ambient 2.
temperature.
Repair Facility.
1-16 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
18. Engine power out- 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
put low Information chart in this section.
2. Fuel suction line or fuel filter is 2. Replace fuel filter or check fuel line
restricted. for restriction and replace if neces-
sary.
3. Oil level is too high. 3. Check oil dipstick and oil pan
capacity. Adjust to the proper oil
level.
4. Intake or exhaust system is 4. Check intake and exhaust systems
restricted. for restrictions. Remove restric-
tions.
5. Air intake or exhaust leak. 5. Check for loose or damaged piping
connections or missing pipe plugs.
Check turbocharger and exhaust
manifold mounting.
6. Air in fuel. 6. Check for air in the fuel, and tight-
en fuel connections and filter.
7. Fuel drain line restriction. 7. Check the fuel lines for restriction.
Clear or replace the fuel lines.
8. Fuel grade is not correct or fuel 8. Refer to Correction 1. of Problem
quality is poor. 17. of this troubleshooting chart.
9. Engine operating above recom- 9. Engine power decreases at 10,000
mended altitude. feet above sea level.
Repair Facility.
19. Engine runs rough 1. Engine operating at low ambient 1. Refer to the Cummins Engine
at idle temperatures. Operation and Maintenance
Manual.
2. Electronic fault codes are active. 2. Refer to the QSM11 Fault Code
Information chart in this section.
3. Engine mounts are worn or dam- 3. Visually check engine mounts and
aged. replace if necessary.
4. Engine idle speed is set too low 4. Verify the correct idle speed set-
(electronically controlled fuel sys- ting.
tems).
5. Air in the fuel. 5. Check for air in the fuel, and tight-
en fuel connections and filter.
7. Overhead adjustments are incor- 7. Measure and adjust the overhead
rect. settings. Refer to the Cummins
Engine Operation and Mainte-
nance Manual.
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 1-17
19. Engine runs rough 8. Contact a Cummins Authorized

at idle Repair Facility.
(Continued)
20. Engine runs rough 1. Condition occurs only at idle. 1. Refer to Problem 19. of this trou-
or misfires bleshooting chart.
2. Engine operating in low ambient 2. Refer to the Cummins Engine
temperatures. Operation and Maintenance
Manual.
3. Electronic fault codes are active. 3. Refer to the QSM11 Fault Code
Information chart in this section.
4. Fuel leak. 4. Check the fuel lines, fuel connec-
tions, and the fuel filters for leaks.
6. Air in the fuel. 6. Check for air in the fuel and tighten
fuel connections and filter.
nance Manual.
Repair Facility.
21. Engine shuts off 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
unexpectedly or Information chart in this section.
dies during decel- 2. Battery voltage supply to the elec- 2. Check the battery connections.
eration tronic control module (ECM) has Check the fuses and the un-
been lost. switched battery supply circuit.
3. Engine will not restart. 3. Refer to Problems 14. and 15. of
this troubleshooting chart.
4. Fuel inlet restriction or air in the 4. Check fuel tank, fuel filter, fuel
fuel. lines, connections and fuel cooling
plate.
5. Low battery voltage. 5. Check battery power supply cir-
cuits.
6. Loose wire on master disconnect 6. Isolate and tighten wire connection.
switch.
7. Fuel cutoff valve is closed. 7. Check for loose wires and power to
the fuel cutoff valve solenoid.
continued quality is poor. 17. of this troubleshooting chart.
1-18 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
21. Engine shuts off 9. Contact a Cummins Authorized

unexpectedly or Repair Facility.
dies during decel-
eration
(Continued)
22. Engine speed 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
surges at low idle Information chart in this section.
or high idle 2. Low fuel level in the tank. 2. Fill fuel tank with fuel.
Repair Facility.
23. Engine speed 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
surges under load Information chart in this section.
or in operating 2. Low fuel level in the tank. 2. Fill fuel tank with fuel.
range
Repair Facility.
24. Engine starts, but 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
will not keep run- Information chart in this section.
ning 2. Low fuel level in tank. 2. Fill fuel tank with fuel.
3. Load on hydraulic pump. 3. Isolate and remove restriction from
hydraulic circuit.
4. Air in the fuel system. 4. Check for air in fuel, tighten fuel
connections and tighten fuel filter.
5. Fuel filter plugged or fuel waxing 5. Replace fuel filter. Weather condi-
due to cold weather. tions can require fuel heater.
6. Fuel inlet restriction. 6. Inspect fuel line for restriction and
replace if necessary.
8. Intake or exhaust system is 8. Check intake and exhaust for
restricted. restriction and remove restriction.
9. Loose wire on master disconnect 9. Isolate and tighten wire connection.
switch.
10. Engine protection circuit is active. 10. Refer to the Engine Protection
System Troubleshooting chart.
11. Fuel cutoff valve is closed. 11. Check for loose wires and power to
the fuel cutoff valve solenoid.
Repair Facility.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 1-19
25. Engine vibration 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
excessive Information chart in this section.
2. Engine is misfiring. 2. Refer to Problem 20. of this trou-
bleshooting chart.
3. Engine idle speed is too low. 3. Adjust idle speed.
4. Fan is loose, damaged or unbal- 4. Check fan. Tighten, replace or
anced. adjust.
5. Engine belt driven accessories 5. Check for interference. Loosen
malfunctioning: fan hub, alternator, belt, if applicable, to isolate compo-
Freon compressor or air compres- nent from vibration.
sor.
7. Damaged vibration damper. 7. Check vibration damper and
replace if required.
Repair Facility.
26. Engine will not 1. Master disconnect switch is turned 1. Turn master disconnect switch on.
crank or cranks off.
slowly (OEM 2. Load on hydraulic pump. 2. Isolate and remove restriction from
electrical) hydraulic circuit.
3. Battery connections are broken, 3. Check for damage. Replace, tight-
loose or corroded. en or clean.
4. Low battery charge. 4. Check electrolyte level and specific
gravity. Recharge or replace bat-
teries.
5. Battery rating is too low or battery 5. Replace with correct rated battery.
is defective.
6. Shifter is not in the neutral position. 6. Place shifter in the neutral position.
7. Circuit breaker (CB2, CB7 or 7. Reset or replace circuit breaker
CB10; Illustration 6-16) is tripped or (CB2, CB7 or CB10).
defective.
8. Circuit breaker (CB1) is defective. 8. Replace circuit breaker (CB1).
9. Defective truck power solenoid 9. Replace truck power solenoid (L1).
(L1).
10. Defective neutral start relay (K1). 10. Replace neutral start relay (K1).
11. Defective starter solenoid (L2). 11. Replace starter solenoid (L2).
12. Defective starter. 12. Replace or repair starter.
13. Defective ignition switch (S1). 13. Refer to Component 4. of the
Component Troubleshooting
chart in Section 6.
continued
1-20 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
26. Engine will not 14. Defective fuel cutoff valve (L4). 14. Refer to Fuel Solenoid Valve
crank or cranks found in Section 2 for proper fuel
slowly (OEM cutoff valve operation.
electrical)
(Continued) 15. Loose or broken wires, pins, or 15. Isolate and repair.
plugs between any of the compo-
nents in Causes 1. thru 14.
27. Engine will not 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
reach rated speed Information chart in this section.
(rpm) 2. Engine power output is low. 2. Refer to Problem 18. of this trou-
bleshooting chart.
4. Fuel suction line is restricted. 4. Check fuel inlet for restriction.
nance Manual.
repair facility.
28. Engine will not 1. Ignition switch circuit is malfunc- 1. Check ignition key switch circuit.
shut off tioning. NOTE: Should an electrical mal-
function prevent engine shutdown,
turn the master disconnect switch
off.
2. Engine is running on fumes drawn 2. Locate and isolate the source of
into air intake. fumes.
29. Fuel consumption 1. Oil level is too high. 1. Check oil dipstick and oil pan
excessive capacity. Adjust to the proper oil
level.
2. Intake air restriction is excessive. 2. Visually inspect air filter and restric-
tion indicator. Replace air filter if
necessary.
3. Fuel leaks. 3. Visually check fuel system and
supply for leaks.
Repair Facility.
30. Fuel in coolant 1. Bulk coolant supply contaminated. 1. Check coolant supply. Drain cool-
ant and replace with non-contami-
nated coolant. Replace coolant
continued
filter.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 1-21
30. Fuel in coolant 2. Contact a Cummins Authorized

(Continued) Repair Facility.
31. Fuel in the lubri- 1. Bulk oil supply is contaminated. 1. Check oil supply. Drain oil and
cating oil replace with non-contaminated oil
and replace filters.
2. Engine idle time is excessive. 2. Low oil and coolant temperatures
can be caused by long periods of
engine idling (time greater than
10 minutes). Shut off the engine
rather than idle for long periods of
time.
Repair Facility.
32. Intake manifold air 1. Truck speed too low for adequate 1. Reduce engine load.
temperature above cooling at high engine load.
specification 2. Cooling fan shroud is damaged. 2. Repair or replace shroud.
3. Fan drive belt is broken. 3. Check the fan drive belt and
replace belt if necessary.
4. Charge air cooler fins, radiator fins, 4. Inspect charge air cooler, radiator,
and Freon condenser fins are dam- and Freon condenser. Clean fins if
aged or obstructed with debris, necessary.
insects, dirt, etc. (external)
Repair Facility.
33. Lubricating oil con- 1. Verify oil consumption rate. 1. Check oil added versus hours.
sumption exces- 2. External oil leaks. 2. Tighten capscrews, pipe plugs and
sive fittings as needed. Replace gas-
kets if necessary.
3. Oil does not meet specifications. 3. Change oil and replace with the
proper oil (refer to Fuel and Lubri-
cant Specifications in the Appen-
dices).
4. Crankcase ventilation system is 4. Check and clean crankcase
plugged. breather and vent tube.
Repair Facility.
34. Lubricating oil con- 1. Identify contamination. 1. Perform an oil analysis to deter-
taminated mine the contaminants.
continued
1-22 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
34. Lubricating oil con- 2. Bulk oil supply is contaminated. 2. Check oil supply. Drain oil and
taminated replace with non-contaminated oil
(Continued) and replace filters.
3. Oil sludge is excessive. 3. Refer to Problem 37. of this trou-
bleshooting chart.
4. Fuel in the oil. 4. Refer to Problem 31. of this trou-
bleshooting chart.
Repair Facility.
35. Lubricating oil 1. Oil pressure switch, gauge or sen- 1. Verify that the oil pressure switch,
pressure (high) sor is malfunctioning. gauge and sensor is functioning
properly.
2. Engine coolant temperature is too 2. Refer to Problem 11. of this trou-
low. bleshooting chart.
3. Oil does not meet specifications. 3. Change the oil with the proper type
of oil (refer to the Fuel and Lubri-
dices).
Repair Facility.
36. Lubricating oil 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
pressure (low) Information chart in this section.
2. Incorrect oil level. 2. Add or drain engine oil.
3. External oil leaks. 3. Visually inspect for oil leaks. Tight-
en the capscrews, pipe plugs, and
fittings. Replace gaskets if neces-
sary.
4. Oil pressure switch, gauge or sen- 4. Refer to Correction 1. of Problem
sor is malfunctioning. 35. of this troubleshooting chart.
5. Oil does not meet specifications. 5. Change oil and filters. Refer to
Fuel and Lubricant Specifica-
tions in the Appendices for the
proper type of oil to be used.
6. Oil contaminated with coolant or 6. Refer to Problem 34. of this trou-
fuel. bleshooting chart.
7. Oil filter(s) are plugged. 7. Change oil and replace oil filter(s).
Repair Facility.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 1-23
37. Lubricating oil 1. Bulk oil supply is contaminated. 1. Refer to Correction 2. of Problem
sludge in the 34. of this troubleshooting chart.
engine crankcase 2. Oil does not meet specifications. 2. Change the oil with the proper type
excessive of oil (refer to the Fuel and Lubri-
dices).
3. Oil drain interval is excessive. 3. Change oil and filter(s) at the
appropriate intervals (refer to the
Preventive Maintenance chart in
the Appendices).
5. Crankcase ventilation system is 5. Check and clean crankcase
plugged. breather and vent tube.
Repair Facility.
38. Lubricating oil tem- 1. Incorrect oil level. 1. Add or drain engine oil.
perature above 2. Engine coolant temperature is 2. Refer to Problem 10. of this trou-
specification above normal. bleshooting chart.
3. Oil pressure switch, gauge or sen- 3. Refer to Correction 1. of Problem
sor is malfunctioning. 35. of this troubleshooting chart.
Repair Facility.
39. Lubricating or 1. Bulk coolant supply contaminated. 1. Check coolant supply. Drain cool-
transmission oil in ant, flush cooling system and
the coolant replace with non-contaminated
coolant. Replace coolant filter.
Repair Facility.
40. Excessive black 1. Turbocharger wheel clearance is 1. Check the radial bearing clearance
smoke out of specification. and axial clearance. Inspect the
turbocharger. Repair or replace
the turbocharger if necessary.
2. Air intake or exhaust leaks. 2. Check for loose or damaged piping
connections or missing pipe plugs.
Check turbocharger and exhaust
manifold mounting.
4. Fuel drain line restriction. 4. Check the fuel lines for restriction.
Clear or replace the fuel lines.
continued
1-24 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
40. Excessive black 5. Contact a Cummins Authorized

smoke Repair Facility.
(Continued)
41. Excessive white 1. Electronic fault codes are active. 1. Refer to the QSM11 Fault Code
smoke Information chart in this section.
2. Engine block heater malfunctioning 2. Check electrical source and wiring
(if equipped). to cylinder block heater. Replace
block heater if necessary.
3. Coolant temperature is too low. 3. Refer to Problem 11. of this trou-
bleshooting chart.
4. Engine is cold. 4. Allow engine to warm to operating
temperature.
5. Fuel grade is incorrect or fuel 5. Refer to Correction 1. of Problem
quality poor. 17. of this troubleshooting chart.
nance Manual.
Repair Facility.
42. Intake manifold 1. Air intake or exhaust leaks. 1. Check for loose or damaged piping
pressure (Boost) is connections or missing pipe plugs.
below normal Check turbocharger and exhaust
manifold mounting.
2. Air compressor connection is loose 2. Check the connection between the
or damaged. manifold and the air compressor.
Repair or replace if necessary.
Repair Facility.
43. Turbocharger 1. Operating for extended periods 1. Refer to the Cummins Engine
leaks engine oil or under light or no load conditions. Operation and Maintenance
fuel Manual.
2. Engine oil or fuel entering turbo- 2. Remove intake and exhaust piping,
charger. and check for oil or fuel.
3. Turbocharger drain line is 3. Remove the turbocharger drain line
restricted. and check for restriction. Clean or
replace the drain line.
Repair Facility.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 1-25
Cummins QSM11-C330 Diesel Engine
Engine Operating Conditions 2100 rpm
Lubrication System English Metric
Lubricating oil pressure (min. / max. at rated speed) . . . . . . . . . . . . . . psi (kPa) 15 - 35 103 - 241
Minimum for safe operation (at idle) . . . . . . . . . . . . . . . . . . . . . . . . . . . . psi (kPa) 10 69
*Lubrication oil temperature maximum . . . . . . . . . . . . . . . . . . . . . . . . . . . °F (°C) 275 135
Oil pan capacity High / Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . qt (L) 36 / 28 34 / 26.5
Total engine oil capacity with filters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . qt (L) 39.2 37
Air System
Air inlet restriction, Dirty air cleaner . . . . . in H2O (mm H2O) 25 635
f ll load maximum
full ma im m
Clean air cleaner . . . . in H2O (mm H2O) 15 381
Exhaust back pressure maximum full load . . . . . . . . . . . . . . . . . . in Hg (mm Hg) 3.0 76
Max. allowable air temp. rise over ambient at turbo compressor inlet . °F (°C) 30 16
Fuel System
Maximum fuel inlet restriction Dirty fuel filter . . . . . . . . . in Hg (mm Hg) 8 203
Clean fuel filter . . . . . . . . in Hg (mm Hg) 4 102
Maximum fuel drain restriction less check valves . . . . . . . . . . . . in Hg (mm Hg) 2.5 63
Maximum fuel flow (on supply side of fuel pump) . . . . . . . . . . . . . . lb/hr (kg/hr) 540 245
Cooling System
Coolant flow Normal temp. . . . . . . . . . . . . . . . . °F (°C) 190 88
Full load speed . . . . . . . . gal/min (L/sec) 62 3.9
Engine coolant capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . qt (L) 13.6 12.9
Min. pressure cap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . psi (kPa) 7 48
Max. pressure cap . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . psi (kPa) 15 103
Max. top tank temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . °F (°C) 212 100
Min. top tank temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . °F (°C) 160 71
Thermostats Start to open . . . . . . . . . . . . . . . . °F (°C) 180 82
Fully open . . . . . . . . . . . . . . . . . . °F (°C) 200 93
*The lubricating oil temperature range is based on the temperature measurement in the oil gallery. When measur-
ing the oil temperature in the pan, it will normally be approximately 10°F higher than the oil gallery temperature.
1-26 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 1-6. Cummins QSM11-C330 Engine Electrical Wiring ANSI Circuit
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 1-27
1-28 THDC
THDC
/ THDCP
/ THDCP
- 954- /954
955/ /955
974/ /974
975/ (Rev.
975 (Rev.
06/03)
5/05)
06B-2196 SHT. 02
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 1-29
Hoist Circuit
1-30 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Hoist Circuit
PLACE THE FOLLOWING ILLUSTRATIONS IN

FOLDER ENVELOPES:
Illustration 1-7 - CUMMINS QSM11 ECM CIRCUIT
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-31

Hoist Circuit
1-32 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Section 2
Fuel System
ENGINE
CYLINDER
HEAD
FUEL
COOLER
FUEL
SOLENOID RETURN LH RH
LINE
SUPPLY
LINE
FUEL
TANK
FUEL / WATER
SEPARATOR
FILTERS FUEL
PUMP
FUEL FLOW
INDICATES FUEL SUPPLY
INDICATES FUEL RECOVERY
Illustration 2-1. Fuel System

Introduction. Fuel is drawn from the tank through tors. The fuel solenoid valve is normally closed
the fuel / water separator filters by the fuel pump. and requires a 12 VDC signal to energize the coil,
From here, the fuel is sent to the fuel injectors. shifting the spool to the open state. This allows
Unused fuel is returned through the fuel cooler the fuel to flow to the injector pump.
and into the fuel tank.
Adding Fuel (Illustration 2-3). When adding die-
Major Components (Illustration 2-1). The fuel sel fuel to the fuel tank, make sure the fuel strain-
system consists of a fuel tank, two fuel / water er is in the filler neck and free of debris. Adding
separator filters, fuel pump, fuel solenoid valve, fuel with the strainer removed could lead to debris
fuel cooler, fuel injectors and fuel lines. entering the fuel tank, resulting in poor engine
performance.
Fuel Solenoid Valve (Illustration 2-1). The fuel
solenoid valve, located on the fuel pump itself, Fuel Cooler (Illustration 2-1). The fuel cooler,
controls the on / off flow of fuel to the fuel injec- located inside the radiator shroud, is forced-air
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 2-1

cooled. Fuel is circulated through its tubes and S Do not overtighten the drain valve. Overtigh-
the engine fan circulates air across the cooler and tening may cause thread damage.
through the fins, cooling the fuel before it returns
to the fuel tank. 1. Provide a suitable container to catch drained
water and open the drain valve approximately
Changing the Fuel / Water Separator Filters 1-1/2 to 2 turns until draining occurs. Drain
(Illustration 2-2). With the engine shut down, per- each fuel / water separator filter of water until
form the following procedures to replace the fuel / clear fuel is visible.
water separator filters. They should be changed
every 250 hours or more often if conditions war- 2. Once the water has drained, turn the valve
rant. clockwise to close the drain valve.

S Dispose of used fuel / water separator filters
and drained fuel in accordance to federal ADAPTER
and local regulations.
S Mechanical tightening of the fuel / water ADAPTER
SEALING
separator filter may result in seal and / or
RINGS
cartridge damage. Tighten the fuel / water
separator filter by hand only.
1. Provide a suitable container to catch drained
fuel and use a strap wrench to remove the fuel
/ water separator filters from the filter base.
2. Clean the area around the filter heads. FUEL / WATER
SEPARATORS
3. Remove the fuel filter thread adapter sealing
rings.
4. Clean the gasket surface of the fuel filter head
with a lint free cloth.
5. Install the new thread adapter sealing rings on
the fuel filter head.
6. Fill new filters with clean fuel and lubricate the Illustration 2-2. Fuel / Water Separator Filters
filter seals with clean oil.
7. Install filters and tighten them 1/2 turn after the
seals contact the filter head surface.
General Information
Fuel Capacity 240 Gallons
Draining The Fuel / Water Separator Filters
(Illustration 2-2). The fuel / water separator filters
should be drained daily to remove water and sedi-
ments from the fuel. Perform the following proce-
dures to drain the water from the fuel / water sep-
arator filters.

S Dispose of drained fuel in accordance to
2-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

COVER PLATE
FILLER CAP FUEL LEVEL

SENDING UNIT
FUEL STRAINER
FILLER NECK
DRAIN PLUG
FUEL TANK
Illustration 2-3. Fuel Tank
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 2-3

1-12 RTGP-9042N (9/01)
Section 3
Air Intake System
COTTER PIN INTERNAL PRECLEANER

FILTER CAP
INDICATOR AIR RESTRICTION
SAFETY INDICATOR
FILTER
IF EQUIPPED
SIGNAL
LINE
SAFETY
FITTING
WING
NUT
PRIMARY VACUATOR
FILTER
AIR
ASSEMBLY
CLEANER
HOUSING
INDICATES AIR FLOW
Illustration 3-1. Air Intake System Components

Introduction. The air cleaner is designed to be Major Components (Illustration 3-1). The air
serviced efficiently and quickly. Intake air enters cleaner consists of the primary filter element, inter-
the air cleaner through the cap or optional pre- nal filter indicator, safety element, air cleaner
cleaner. When the air reaches the filter body, a housing, cap (or optional precleaner), vacuator
helical ramp imparts a high-speed circular motion and an air restriction indicator.
to the intake air. This action separates up to 85%
Servicing (Illustration 3-1). If the equipment is
of the dust from the air by centrifugal action. The
being operated under extremely dusty conditions,
dust is then forced out the vacuator. The air then
the vacuator should be checked every day to be
passes through the primary and safety elements,
certain it is not clogged. Perform the following
where it is cleaned, before entering the engine.
procedures to service the filter element and air
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 3-1

cleaner components. Overservicing of the filter 8. Re-install wing nut, washer and clip on
elements is not recommended. Filter element effi- replacement primary filter element. Re-install
ciency increases with initial operation. and secure the primary filter assembly in the
air cleaner housing.
9. Push the reset button on the top of the air

S Normally the primary filter element should restriction indicator.
be changed after 1500 hours of operation or 10. Inspect air intake system for leaks.
when the air restriction indicator shows red.
In dusty conditions, the primary filter 11. Inspect rubber elbow, joints and clamps for
element may have to be changed more often. wear, damage and looseness.
S Replace the safety element when the internal 12. Inspect the vacuator cup joint for sealing.
filter indicator turns red, yearly or every
3000 hours, whichever comes first.
S Do Not use ether type fuels to help start the
engine for this may damage the engine.
1. When the air restriction indicator indicates ele-
ment servicing is required, remove the wing
nut and cover assembly, then remove the pri-
mary filter assembly. In high humidity situa-
tions, the air restriction indicator may indicate
a restricted condition due to moisture in the
filter element. When the element dries out, GREEN DOT
restriction levels drop back to normal. The
indicator will now have to be reset (refer to
procedure 9. to reset the indicator).
Illustration 3-2. Internal Filter Indicator
2. Check the internal filter indicator to determine
if the safety element also requires servicing.
3. If the internal filter indicator indicates a green
dot in its center (Illustration 3-2), the safety
element is good, continue to procedure 6.
4. If the internal filter indicator indicates red, the
safety filter element must be replaced.
Remove internal filter indicator, old safety filter
and replace with a new safety filter element.
5. Reset the internal filter indicator by applying
suction to window and re-install indicator.
6. Remove all dust and foreign particles from the
air cleaner components, and clean the inside
of the air cleaner housing with a damp cloth.
Do not use flammable liquids

to clean the inside of the air cleaner housing.
Only use a cloth dampened with water.
7. Replace the primary filter element with a new
filter element. Remove clip from the used pri-
mary filter element to release the wing nut and
washer.
3-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Air Intake System Troubleshooting
1. Short element life 1. Improper assembly when prior ele- 1. Properly install.
(primary filter element was replaced.
ment)
2. Damaged or missing vacuator. 2. Replace vacuator.
3. Damaged seal on the cover. 3. Replace seal on the cover.
4. Damaged air cleaner body. 4. Replace air cleaner body.
5. Loose system connections. 5. Tighten system connections.
6. Loose wing nut on cover. 6. Tighten wing nut.
7. Excessively dusty environment. 7. Replace element as needed.
8. Incorrect element used. 8. Replace with proper element.
9. Seal on dust cover is not sealing. 9. Ensure that no foreign object is
between seal and metal mating
surface.
2. Short element life 1. Bypassing primary filter element. 1.

(safety element)
a. Seal of primary filter element is a. Replace element.
not sealing.
b. Damaged primary element. b. Replace primary filter element.
c. Loose primary filter element c. Tighten wing nut.
wing nut.
3. Airborne contami- 1. Damaged element(s). 1. Replace element(s).

nants entering the
engine 2. Damaged seals or sealing sur- 2. Replace damaged components.
faces.
3. Damaged or loose connections 3. Replace or repair connections.
between air cleaner body and
engine.
4. Incorrect element used. 4. Replace with proper element.
4. Air restriction indi- 1. Restriction in air hose between the 1. Remove restriction.
cator indicates air restriction indicator and the
green condition safety fitting.
and primary filter
element is clogged 2. Air leak in air hose between the air 2. Repair or replace air hose.
restriction indicator and the safety
fitting.
3. Damaged air restriction indicator. 3. Replace air restriction indicator.
4. Damaged safety fitting. 4. Replace safety fitting.
5. Loose system connections. 5. Tighten connections.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 3-3

1-12 RTGP-9042N (9/01)
Section 4
Exhaust System
Introduction. The exhaust system is responsible
for venting exhaust gases, generated by the
engine, to the atmosphere. It also provides noise
suppression.

S Do not service exhaust system until exhaust
system is cool. Failure to do so may result
in severe burns.
S Keep all flammable materials away from
exhaust components.
S Avoid breathing toxic exhaust fumes.
S All internal combustion engines produce
carbon monoxide, which can become con-
centrated in enclosed areas. Exposure to
carbon monoxide can result in serious inju-
ries or health hazards, including death.
Properly ventilate work areas, vent exhaust
fumes, and keep shop clean and dry.
(A) Initial symptoms of carbon monoxide
poisoning include headaches, dizzi-
ness, and nausea. The smell of lift truck
exhaust means carbon monoxide is
present.
(B) If you experience initial symptoms, shut
off the lift truck engine, notify your
employer, and obtain medical attention.
S Never rely on a control device to reduce car-
bon monoxide output. Carbon monoxide
levels can change depending on mainte-
nance. Make sure carbon monoxide level
testing is included in regular maintenance
procedures and that ventilation is used as
the primary control for emissions.
Maintenance. There is minimal maintenance re-
quired on the standard exhaust system.
1. Check for leaks at all pipe connections.
2. Check for holes in the muffler and exhaust
piping.
3. Keep guard clean and in place.
4. Keep exhaust system free of debris.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 4-1

1-12 RTGP-9042N (9/01)
Section 5
Cooling System
Introduction. The cooling system cools the
engine. Refer to Section 9A for transmission Coolant containing anti-leak
cooling and Section 15C for the wet disc brakes additives must not be used with the coolant
cooling system to find more detailed cooling infor- filter because it will clog the element.
mation on these particular systems.
Major Components (Illustration 5-5). The engine
cooling system consists of coolant, radiator /
charge air cooler, piping connecting the radiator to CUT-OFF
the engine and a water pump to circulate the cool- VALVES
ant. A coolant filter, remote mounted, is used to
filter and condition the coolant.
Operation (Illustration 5-5). When the engine is
started, the water pump draws coolant from the
radiator into the engine block. The coolant is cir-
culated through the engine and the coolant filter
until it reaches a temperature of approximately
180_F, at which point the thermostat will start to
open. This will allow coolant flow back into the top
of the radiator core. Air trapped in the coolant will
travel to the top of the deaeration space by means COOLANT
of the deaeration line and an internal deaeration FILTER
stand tube. Coolant is made available from the
deaeration tank to displace the removed air by
way of the make-up line.
Coolant. The cooling system of this equipment is
protected to -34_F (-36_C) and 228_F (108.9_C).
The solution is a 50 - 50 mixture of ethylene glycol Illustration 5-1. Coolant Filter
base antifreeze to water solution. Use soft water
in the coolant mixture. It is recommended that Radiator / Charge Air Cooler (Illustration 5-4).
50% solution be maintained year round. The radiator is comprised of a deaeration tank,
core, and a charge air cooler. The deaeration
A proper coolant / SCA (Supplemental Coolant
tank functions as a coolant storage tank. When
Additive) additive concentration must be main-
adding coolant to the system, coolant should be
tained to prevent liner pitting, corrosion and scale
added to the deaeration tank. Access to the
deposits in the cooling system. Refer to the
deaeration tank is supplied through a 7 psi radia-
Cummins QSM11 Engine Operation and Mainte-
tor cap located on the left side of the radiator,
nance Manual for coolant additive concentration.
above the radiator sight glasses. The radiator
The coolant additive concentration level may be coolant level is to be maintained by the coolant
tested with a coolant test kit, Taylor part number sight glasses below the 7 psi radiator cap.
1006-175.
The radiator is force-air-cooled. Access to the
core is supplied through a 15 psi radiator cap
Insufficient concentration of located on the right side of the radiator. When the
the coolant additives will result in liner pitting cooling system has been completely drained, the
and engine failure. 15 psi radiator cap neck will allow a quicker, more
efficient method of refilling the cooling system.
Coolant Filter (Illustration 5-1). The coolant filter
is used in the cooling system to control the water Charge Air Cooler (Illustration 5-4). The QSM11
acidity, soften the water to reduce scale formation, engine is equipped with a turbocharger. The
filter out suspended materials and add a corrosion turbocharger is driven by the exhaust from the
inhibiting chemical to the coolant which provides a engine. The exhaust turbine of the turbocharger is
protective film on the water passages. coupled to the intake turbine. The exhaust turbine
drives the intake turbine. The intake turbine com-
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.1/05)
06/03) 5-1
presses the intake air. The act of compressing the
intake air generates heat and causes the air mole-
cules to expand. To increase combustion efficien- S Dispose of coolant filter in accordance with
cy, a charge air cooler is integrated into the radia- federal and local regulations.
tor. The charge air cooler is an air to air cooler. S Do not use a strap wrench to tighten the
By reducing the temperature of the intake air coolant filter. Mechanical over-tightening
before it enters the piston chamber, the air may distort the threads or damage the filter
becomes denser (the air molecules get smaller). gasket.
The denser the air, the more oxygen that will be
present in the piston chamber during combustion. 1. Close both cut-off valves (Illustration 5-1).
The more oxygen in the chamber, the hotter the 2. Remove the coolant filter. It may be possible
combustion cycle becomes. This results in a more to unscrew the coolant filter by hand; however,
complete burning of the fuel, emitting fewer pollu- a band type filter wrench may be used if nec-
tants. This increase in combustion efficiency also essary.
creates lower engine operating temperatures,
which pro-long the life of the engine and its com- 3. Clean the gasket surface of the filter base.
ponents. 4. Apply a light film of lubricating oil to the gasket
Checking The Coolant Level (Illustration 5-2). sealing surface of the new coolant filter.
The coolant level should be checked daily with the 5. Screw the new coolant filter onto the filter
engine cool. The coolant level is full when the base until the gasket comes in contact with the
coolant is visible at the center of the upper coolant filter base and then tighten filter 1/2 to 3/4 turn
sight glass on the radiator. If the coolant level is by hand only.
visible at the lower coolant sight glass, add cool-
ant until the coolant level is visible at the center of 6. Open the cut-off valves.
the upper coolant sight glass on the radiator. 7. Start up engine and check for leaks at the
Cooling Requirements. The following require- coolant filter base.
ments must be followed for trouble-free operation Draining / Flushing The Cooling System. The
of the cooling system. cooling system should be drained and flushed
1. Always use a properly corrosion inhibited every 2 years or 6000 hours, whichever comes
coolant. first. The cooling system is drained by opening
the drain cock on the bottom of the radiator.
2. Maintain prescribed inhibitor strength. Removal of the 15 psi radiator cap will allow air to
3. Use low silicate antifreeze with an ethylene enter the cooling passages, decreasing drain time
glycol base. and ensuring that the coolant drains completely
from the system. Leave the drain cock open until
4. Always follow the manufacturer’s recommen- all coolant has been allowed to drain from the sys-
dations on inhibitor usage and handling. Refer tem.
to the engine operation and maintenance
manual for coolant requirements.
5. Do Not use soluble oil!

S Shut down the engine and allow the engine
6. Sealer type antifreeze should Not be used. to cool before opening the radiator cap and
Changing the Coolant Filter. Refer to the engine the drain cock to drain the cooling system.
operation and maintenance manual for the coolant S Coolant should only be added to the cooling
filter change interval. Perform the following proce- system when the engine has been shut down
dures to replace the coolant filter. and allowed to cool. Failure to do so may
result in personal injury from heated coolant
spray.

Shut down the engine and
allow the engine to cool before changing the S Dispose of coolant in accordance with
coolant filter. federal and local regulations.
5-2 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
1/05)
06/03)
gauge should be in the green temperature area
When freezing weather is (180_F - 210_F). The thermostat will start to open
expected, any cooling system not adequately at approximately 180_F and fully open when the
protected by antifreeze should be drained. coolant temperature reaches approximately
201_F.
Filling The Cooling System. Before starting the
engine, close the drain cock of the radiator and fill General Information
the cooling system. Remove the 15 psi radiator
cap and fill the core of the radiator. Remove the Coolant Capacity 17 Gallons
7 psi cap and fill the deaeration tank to the upper
sight glass. Start the engine to remove air from Inspection. Components of the cooling system
the coolant. Recheck the coolant level at the sight should be checked periodically to keep the engine
glasses and add coolant as required to obtain the operating at peak efficiency. The radiator should
proper level. be inspected externally for excessive dirt or oil
buildup. The radiator should be cleaned external-
ly as conditions warrant. The cooling system

Coolant should only be added hoses should be inspected and any hose that is
to the cooling system when the engine has abnormally hard or soft should be replaced imme-
been shut down and allowed to cool. Failure diately. Check the hose clamps to make sure they
to do so may result in personal injury from are tight. All external leaks should be corrected
heated coolant spray. as soon as detected. The shroud should be tight
against the radiator core to prevent recirculation of
air which may lower cooling efficiency. Check the
The 15 psi radiator cap is a fan belts for proper tension.
sealing cap. Be sure it is installed securely Drive Belt Tension. The proper tension should
after the coolant has been added. be maintained on all drive belts. Refer to Drive
Belt Tension in Section 1 for the proper tension
Coolant Temperature. When the engine warms values.
up, the indicator for the coolant temperature
15 PSI
DEAERATION PRESSURE
CAP
7 PSI
PRESSURE
CAP
COOLANT
LEVEL
SENSOR
MAKE-UP ADD LEVEL

LINE FULL LEVEL SIGHT GLASS
SIGHT GLASS
Illustration 5-2. Checking The Coolant Level
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 5-3

15 PSI PRESSURE CAP
RADIATOR / CHARGE 7 PSI PRESSURE CAP

AIR COOLER TRANSMISSION
OIL COOLER
WET DISC BRAKES
OIL COOLER
SHROUD
FAN
PLATE
FUEL
COOLER
Illustration 5-3. Cooling Components Identification
CHARGE AIR
COOLER
RADIATOR
Illustration 5-4. Radiator / Charge Air Cooler
5-4 THDC
THDC
/ THDCP
/ THDCP
- 954- 954
/ 955/ 955
/ 974/ 974
/ 975/ 975
(Rev.(Rev.
3/05)
06/03)
Illustration 5-5. Cooling System Circuit
COOLANT DEAERATION LINE
ÍÍ ÍÍ
FILTER
ÍÍ
ÍÍ Í
Í
ÍÍ UPPER RADIATOR
ÍÍ HOSE
Í
Í
Í
Í
ÇÇ
ÇÇ
ÇÇ
MAKE-UP
LINE
Ç
RADIATOR
CUMMINS QSM11-C330
Ç
ENGINE
Ç
LOWER RADIATOR
HOSE
Í
COOLANT FLOW
MAIN FLOW, THERMOSTAT OPEN
ÍÇ DEAERATION REMOVES UNWANTED AIR FROM COOLING CIRCUIT

COOLANT FILTER FLOW
MAKE UP FLOW
05-2355
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 5-5
1-12 RTGP-9042N (9/01)
Section 6
Electrical System
Introduction. This machine incorporates a parts. Clean and re-apply a light coating of
12-volt DC electrical system. Optional equipment grease to the terminals and cable clamps
selected by the customer will determine the elec- when necessary.
trical equipment to be installed in addition to the
standard electrical system. NOTE: A number of devices and applications are
Major Components. The 12 volt DC electrical available on the commercial market to deter corro-
system consists of two batteries, battery charging sion on battery terminal connections.
alternator, voltage regulator, starter switch, starter 4. Check the electrical system if the battery
and starter solenoid. The remainder of the electri- becomes discharged repeatedly.
cal system consists of lights and / or gauges,
switches, circuit breakers and accessory circuits. 5. If the battery indicator illuminates, the alterna-
The above items are included as standard equip- tor or alternator circuit is defective.
ment in the electrical system. Refer to Illustrations
6-1 through 6-16 for location of components and NOTE: If the truck is to be inoperative or idle for
wiring diagrams. more than 30 days, remove the battery. The bat-
Batteries. This machine is equipped with two tery should be stored in a cool, dry place. The
industrial type, long life batteries. The batteries electrolyte level should be checked regularly and
are perishable and require servicing on a regular the battery kept fully charged.
basis. Batteries that are properly cared for can be Booster Battery Connection Procedure. Acci-
expected to give long trouble-free service. Per- dentally reversing the battery connections must be
form the following procedures to maintain the bat- avoided. If a booster battery is to be used, first
teries in a serviceable condition. connect the positive (+) terminal of booster battery
to the positive (+) terminal of discharged battery

and then connect the negative (-) terminal of
S Under no circumstances allow any sparks or booster battery to engine or body ground (-)
open flames around batteries. No smoking. (Refer to the decal below). Never cross polarity of
Batteries produce a highly flammable gas the battery terminals. Disconnect cables in the
which could lead to battery explosion if exact reverse order from above.
ignited.
S Never check the battery by placing a metal DANGER
object across the battery posts.
Overfilling cells of the battery

can cause poor performance or early failure. SMOKING, FLAMES, ARCS, OR SPARKS MAY RESULT IN BATTERY EXPLOSION.
KEEP METAL TOOLS AWAY FROM BATTERY TERMINALS.

1. The battery’s electrolyte level should be BATTERY CONTAINS SULFURIC ACID WHICH WILL BURN SKIN ON CONTACT;
checked monthly or every 250 hours, whichev- WEAR RUBBER GLOVES AND EYE PROTECTION WHEN WORKING WITH BATTERY.
FLUSH WITH WATER AND SEEK MEDICAL ATTENTION IN CASE OF CONTACT.
er comes first. Add distilled water if necessary
to bring the electrolyte level to 3/8 inch above WHEN JUMP STARTING:
the separator plates. Do not overfill. DO NOT LEAN OVER BATTERY WHEN MAKING CONNECTION.
FIRST CONNECT POSITIVE (+) TERMINAL OF BOOSTER BATTERY TO
POSITIVE (+) TERMINAL OF DISCHARGED BATTERY.
2. Keep the top of the battery, terminals and THEN CONNECT NEGATIVE (-) TERMINAL OF BOOSTER BATTERY TO ENGINE OR
cable clamps clean. When necessary, wash BODY GROUND (-). NEVER CROSS POLARITY OF TERMINALS.
DISCONNECT CABLES IN EXACT REVERSE ORDER.
them with a solution of baking soda and water, 3375 245
and rinse with clean water.

Alternator. The standard alternator for the Cum-
mins QSM11-C330 engine is a 160 amp alterna-
Do not allow the soda and tor. It should be expected to give long, trouble-
water solution to enter the battery cells. free service; however, the diodes and transistors
in the alternator circuit are very sensitive and can
3. Inspect the cables, clamps and hold down be easily destroyed. The following precautions
bracket regularly. Replace any damaged
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 6-1
should be observed when working on or around Never disconnect the battery while the alternator
the alternator. is in operation. Disconnecting the battery will
result in damage to the diodes, caused by the
Avoid grounding the output wires or the field wires
momentary high voltage and current induced by
between the alternator and the regulator. Never
the instantaneous collapse of the magnetic field
run an alternator on an open circuit.
surrounding the field windings.
Grounding an alternator’s output wires or termi-
nals, which are always hot regardless of whether
or not the engine is running or accidentally revers- Accidentally reversing the
ing of the battery polarity, will destroy the diodes. battery polarity will destroy the diodes of the
Grounding the field circuit will also result in the alternator circuit.
destruction of the diodes. Some voltage regula-
tors provide protection against some of these cir- NOTE: It is normal for the alternator light to stay
cumstances; however, it is recommended that on when the engine is started. Once the engine is
extreme caution be used. accelerated, the light should go out.
06-2447 SHT. 01
Illustration 6-1. Dash Panel
6-2 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
5/05)
CB5 CB4 CB24 CB3 CB2
(15 (20 (15 (15 (10
amp) amp) amp) amp) amp)
GAUGES, FRONT REAR TOP IGNITION

PANEL LIGHT, WIPER WIPER WIPER SWITCH
DIAGNOSTIC
LIGHTS POWER,
& BUZZER
FRONT RIGHT SIDE
CB6 CB7 CB8 CB9 CB10

(15 (20 (15 (15 (10
amp) amp) amp) amp) amp)
WORK ECM HEATER ELECTRIC

LIGHTS POWER SHIFT
DEFROSTER
FRONT LEFT SIDE
Illustration 6-2. Dash Circuit Breakers
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 6-3

CB13 (15 amp) DOME LIGHT, CAB FANS
CB14 (15 amp) AIR SEAT, AUTOSHIFT
CB15 (15 amp) BACK ALARM, ENABLE

RELAY, STROBE, HORN RELAY
CB16 (38 amp) AIR CONDITIONER /

HEATER UNIT
CB11 (20 amp) REAR CAB LIGHTS

CB12 (20 amp) FRONT CAB LIGHTS
AUX. LIGHTS
AUX. LIGHTS
Illustration 6-3. Cab Rear Panel Circuit Breakers
6-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Component Troubleshooting Circuit Breakers. Circuit breakers are employed
in the electrical system and act similar to fuses,
Alternator. The alternator provides 13.8 - 14.4
protecting the electrical circuits and valuable com-
VDC at 160 amps of power for the electrical sys-
ponents from overloads which could damage
tem and trickle charges the battery when the
them. Perform the following troubleshooting pro-
engine is being operated. When the alternator is
cedures to troubleshoot a circuit breaker.
started, it will output 6 VDC to a relay (K3), ener-
gizing the relay and taking away the ground from 1. Turn the ignition key to the “Ignition” position.
the Battery light (DS3, Illustration 6-15) on the
2. If the circuit breaker is tripped, reset the circuit
instrument panel.
breaker.
The most effective way to troubleshoot an alterna-
3. If the circuit breaker immediately retrips,
tor is with an ammeter on the output of the alter-
remove all wires from the output side (load
nator. Another good check is with a voltmeter
side) of the circuit breaker.
across the battery. With the engine operating at a
moderate speed, the voltmeter reading should 4. Reset the circuit breaker. If the circuit breaker
never exceed 15.5 VDC. If reading exceeds 15.5 retrips, the circuit breaker is bad and must be
VDC, the alternator is defective and requires replaced.
replacing. Should the alternator output drop
5. If the circuit breaker maintains a set state, one
below 12 VDC, the alternator is defective and
of the output circuits is shorted. Reconnect
requires replacing.
the wires one by one to the output side (load
Perform the following procedures below for abnor- side) until the circuit breaker trips. Trouble-
mal charging system operation. shoot the circuit of the wire, that tripped the
circuit breaker, for a short.
1. Insure that the undercharged condition (below
12 VDC) has not been caused by accessories 6. Isolate and remove the short from the circuit.
having been left on for extended periods of
Automatic 90 amp Circuit Breaker (Illustration
time.
1-5). The automatic circuit breaker (CB1) is
2. Check the drive belt for proper tension (refer to located on the right side of engine. It will automat-
Alternator Drive Belt Tension in Section 1). ically reset itself if it trips. If the circuit breaker
cannot maintain a set state, perform the following
3. Ensure that battery is good and capable of
troubleshooting procedures to troubleshoot the
holding a charge.
automatic circuit breaker.
4. Inspect the wiring for defects. Check all con-
1. Turn the ignition key to the Off position.
nections for tightness and cleanliness, includ-
ing the slip connectors at the alternator and 2. Remove all wires from the output side (load
connections at the battery. side) of the circuit breaker.
5. With the ignition switch on and all wiring har- 3. Turn the ignition key to the “Ignition” position.
ness leads connected, connect a voltmeter If the circuit breaker retrips, the circuit breaker
from: is bad and must be replaced.
a. alternator “BAT” terminal to ground 4. If the circuit breaker maintains a set state, one
of the output circuits is shorted. Reconnect
b. alternator #1 terminal to ground
the wires one by one to the output side (load
c. alternator #2 terminal to ground side) until the circuit breaker trips. Trouble-
shoot the circuit of the wire, that tripped the
An infinity reading indicates an open circuit circuit breaker, for a short.
between the voltmeter connection and bat-
5. Isolate and remove the short from the circuit.
tery. Repair if required.
Single-Pole, Single-Throw 30 amp Relays
6. With all accessories turned off, connect a volt-
(Illustration 6-4). A relay is nothing more than an
meter across the battery. Operate engine at
electrically controlled switch. Relays are always
moderate speed. If voltage is 15.5 VDC or
shown on electrical circuits in a de-energized
higher, replace the alternator.
state. The internal switch, common at pin 30,
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 6-5
toggles between pins 87A (when de-energized) VDC required at pin 86 was or was not present, or
and 87 (when energized). Pins 86 and 85 of the ground signal at pin 85 was or was not present,
relay will energize the coil of the relay. Pin 85, in dependant on the desired state of relay (ener-
all cases, is always the ground side and pin 86, in gized or de-energized), the relay is bad and must
all cases, is always the hot side. Either signal can be replaced.
be sent to the relay to energize it. Ensure that pin
Single-Pole, Single-Throw 10 amp Relays with
85 is properly grounded, when required, and / or
L.E.D.s (Illustration 6-5). A relay is nothing more
that 12 VDC is present at pin 86 when it is
than an electrically controlled switch. Relays are
required.
always shown on electrical circuits in a de-ener-
When the relay is de-energized, the internal gized state. The positive side of the relay coil is
switch connects pins 30 and 87A completing the pin 14 while the negative side of the coil is pin 13.
circuit of the two pins. When the relay is ener- Either signal, 12 VDC or ground (or both), can be
gized, the coil shifts the switch, connecting pins sent to the relay coil to energize the relay.
30 and 87 completing the circuit of the two pins.
When the relay is de-energized, the internal
The most effective way to troubleshoot the relay is switch connects pins 9 and 1 completing the cir-
with an ohmmeter. This can be accomplished by cuit of the two pins. When the relay is energized,
removing the female spade connectors from pins the coil shifts the switch, connecting pins 9 and 5
30, 87, and 87A. In a de-energized state, ensure completing the circuit of the two pins.
that pins 30 and 87A have continuity between
When the L.E.D. is illuminated, the coil of the relay
them. With an ohmmeter, check the resistance
is energized. This does not indicate that the con-
between pins 30 and 87a. The ohmmeter should
tact points of the internal switches are functioning
indicate a reading of 0 - 40 ohms. Energize the
properly. Do not rely on the L.E.D. to give the full
relay and check the resistance between pins 30
operational status of the relay.
and 87. The ohmmeter should indicate a reading
of 0 - 40 ohms. If these two checks are good, the The most effective way to troubleshoot this type
relay is good. If one of these checks fails and 12 relay is with an ohmmeter. This can be accom-
plished by removing the wires at relay socket ter-
Normally Closed minals 9, 5, and 1. In a de-energized state, en-
Common Contact (when relay sure that terminals 9 and 1 have continuity
Contact is de-energized) between them. With an ohmmeter, check the re-
Normally Open
sistance between terminals 9 and 1. The ohmme-
Contact (when relay ter should indicate a reading of 0 - 40 ohms. En-
is de-energized) ergize the relay and check the resistance between
terminals 9 and 5. The ohmmeter should indicate
a reading of 0 - 40 ohms. If these two checks are
good, the relay is good. If one of these checks
fails and 12 VDC required at terminal 14 was or
was not present, or ground signal at terminal 13
was or was not present, dependant on the desired
state of relay (energized or de-energized), the
relay is bad and must be replaced.
Double-Pole, Double-Throw 10 amp Relays
with L.E.D.s (Illustration 6-6). A relay is nothing
more than an electrically controlled switch. Relays
are always shown on electrical circuits in a de-en-
ergized state. The positive side of the relay coil is
pin 14 while the negative side of the coil is pin 13.
Either signal, 12 VDC or ground (or both), can be
sent to the relay coil to energize the relay.
When the relay is de-energized, the internal
Illustration 6-4. SP, ST 30 amp Relay switch connects pins (9 and 1) and pins (12 and
4) completing the circuit of both sets of pins.
6-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

indicate a reading of 0 - 40 ohms. If these two
checks are good, the relay is good. If one of
these checks fails and 12 VDC required at termi-
nal 14 was or was not present, or ground signal at
terminal 13 was or was not present, dependant on
the desired state of relay (energized or de-ener-
gized), the relay is bad and must be replaced.
1
5
14
13
5 1
4
8
14 13
Illustration 6-5. SP, ST 10 amp Relay
When the relay is energized, the coil shifts the

switch, connecting pins (9 and 5) and pins (12 and
8) completing the circuit of both sets of pins. 9
properly. Do not rely on the L.E.D. to give the full 12
Illustration 6-6. DP, DT 10 amp Relay
The most effective way to troubleshoot this type
relay is with an ohmmeter. This can be accom-
plished by removing the wires at relay socket ter- Double-Pole, Double-Throw 15 amp Relays
minals (12, 8, and 4) and terminals (9, 5, and 1). (Illustration 6-7). A relay is nothing more than an
In a de-energized state, ensure that terminals (9 electrically controlled switch. Relays are always
and 1) and terminals (12 and 4) have continuity shown on electrical circuits in a de-energized
between them. With an ohmmeter, check the state. The positive side of the relay coil is pin 14
resistance between terminals (9 and 1) and termi- while the negative side of the coil is pin 13. Either
nals (12 and 4). The ohmmeter should indicate a signal, 12 VDC or ground (or both), can be sent to
reading of 0 - 40 ohms. Energize the relay and the relay coil to energize the relay.
check the resistance between terminals (9 and 5) When the relay is de-energized, the internal
and terminals (12 and 8). The ohmmeter should switch connects pins (9 and 1) and pins (12 and
THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
07/03)
06/03) 6-7
4) completing the circuit of both sets of pins. minal 14 was or was not present, or ground signal
When the relay is energized, the coil shifts the at terminal 13 was or was not present, dependant
switch, connecting pins (9 and 5) and pins (12 and on the desired state of relay (energized or de-en-
8) completing the circuit of both sets of pins. ergized), the relay is bad and must be replaced.
The most effective way to troubleshoot this type Double-Pole, Double-Throw Latching Relays
relay is with an ohmmeter. This can be accom- (Illustration 6-8). A relay is nothing more than an
plished by removing the wires at relay socket ter- electrically controlled switch. This type of relay is
minals (12, 8, and 4) and terminals (9, 5, and 1). shown in a reset state. A latching relay has a
In a de-energized state, ensure that terminals (9 power saving feature. It does not require the relay
and 1) and terminals (12 and 4) have continuity coil to be energized at all times to maintain the set
between them. With an ohmmeter, check the state. The positive side of the relay coil is pin 14
resistance between terminals (9 and 1) and termi- while the negative side of the coil is pin 13 for the
nals (12 and 4). The ohmmeter should indicate a set state of the relay. The internal red flag of the
reading of 0 - 40 ohms. Energize the relay and relay will be visible in the small window, located at
check the resistance between terminals (9 and 5) the top of relay’s cover, indicating a set state. In a
and terminals (12 and 8). The ohmmeter should set state, pins (10 and 5) and pins (6 and 8) of the
indicate a reading of 0 - 40 ohms. If these two relay will be closed and continuity exists between
checks are good, the relay is good. If one of each set of pins. In a reset state, the positive side
these checks fails and 12 VDC required at ter- of the relay coil is pin 12 while the negative side of
the coil is pin 9. In a reset state, pins (10 and 1)
and pins (6 and 4) of the relay will be closed and
continuity exists between each set of pins. The
internal red flag of the relay will not be visible in
the small window in the top of the relay’s cover,
indicating a reset state. A constant 12 VDC signal
is not required to set or reset the latching relay. A
momentary 12 VDC signal is required at either the
set or reset coil, depending on the desired state of
the relay, to set or reset the relay.
minals (10, 1, and 5) and (6, 8, and 4). Set the
relay by applying 12 VDC to pin 14. In a set state
5 1
(the internal red flag is visible in the window),
4 ensure that terminals (10 and 5) and (6 and 8)
have continuity between them. With an ohmme-
ter, check the resistance between terminals (10
8
14 and 5) and then terminals (6 and 8). The ohmme-
13
ter should indicate a reading of 0 - 40 ohms.
Reset the relay by applying 12 VDC to pin 12 (the
internal red flag should not be visible in the win-
dow). Check the resistance between terminals (6
and 4) and then terminals (10 and 1). The ohm-
meter should indicate a reading of 0 - 40 ohms. If
9 these four checks are good, the relay is good. If
one of these checks fails and 12 VDC required at
terminals (14 or 12) was or was not present and
ground signal at terminals (13 or 9) was present,
12 dependant on the desired state of relay (set or
reset), the relay is bad and must be replaced.
Illustration 6-7. DP, DT 15 amp Relay
6-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

and orange wires. The white and orange wires
will have continuity between them only as long as
the proximity switch senses its target. The maxi-
mum targeting distance is approximately 3/8”.
The most effective way to troubleshoot the prox-
imity switch is with an ohmmeter. This can be
accomplished by disconnecting the weatherpack
connector (located approximately 3 foot from the
proximity switch), jumpering the red wires at each
end and jumpering the black wires at each end.
Target the proximity switch (the red L.E.D. should
illuminate) and check the continuity of the white
and orange wires located on the proximity switch
side of the weatherpack. The ohmmeter should
indicate a reading of 0 - 40 ohms. Remove the
target from the proximity switch and with an ohm-
meter, check the continuity between the white and
orange wires. The ohmmeter should now read
2
5 1 infinity If these two checks are good, the proximity
6 switch is good. If one of these checks fails, the
4 proximity switch is bad and must be replaced. Do
14
13 not rely on the red L.E.D. as a sole indicator that
the internal switch did, in fact, close. Always
8
check the continuity between the white and
orange wires as described above.
L.E.D.
10
12
Illustration 6-8. DP, DT Latching Relay
30mm Proximity Switches (Illustration 6-9). The

proximity switches employed on Taylor equipment
are state-of-the-art switching devices. The red
wire of the proximity switch powers the proximity
switch itself and also powers the red L.E.D. on the
cable side of the proximity switch. The black wire
is the ground side of the proximity switch while the
white wire is the common post of the internal
switch. The blue wire is the normal closed post of
the internal switch and the orange wire is the nor- RED BLUE
NC
mally open post of the internal switch. WHITE
COM.
The proximity switch will be energized when the BLACK ORANGE NO
proximity switch senses its target. Once this hap-
pens, the red L.E.D. will illuminate and the internal
switch will switch, closing the circuit of the white Illustration 6-9. Proximity Switch
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 6-9

Single-Pole, Single-Throw, Maintain Contact Exercise care not to reverse polarity because
Switches. A switch is designed with the purpose some solenoids employ internal diodes which can
of controlling an electrical circuit by completing or be destroyed when the polarity is reversed. The
opening the circuit. With an ohmmeter, check the solenoids employed on the transmission control
resistance between the contact points of the valve contain diodes. The black wire of the coil
switch. With the switch closed (completing the connects to the ground side of the circuit while the
circuit), the ohmmeter reading should indicate 0 - red wire goes to the positive side of the circuit.
40 ohms. With the switch open (opening the cir-
Diodes (Illustration 6-10). Diodes are one-way
cuit), the ohmmeter reading should be infinity. If
conductors that provide isolation. Current flow
the above checks are good, the switch is good. If
through a diode is from anode to cathode. They
any of the above checks fail, the switch is bad and
are easily proven good by using an ohmmeter.
must be replaced.
When using the ohmmeter, place the leads of the
Single-Pole, Double-Throw, Momentary Rocker ohmmeter on the opposite ends of the diode.
Switches. This type of switch operates on the Observe the ohmmeter reading. Then reverse the
principle that the circuit is closed only when the ohmmeter leads on the ends of the diode.
switch is held in the closed state. Once the switch Observe the ohmmeter reading. The ohmmeter
is released, the circuit will open. This switch is readings should indicate a higher ohm resistance
checked like an On-Off switch with the exception in one direction opposed to the other direction
that the switch must be held closed to complete because the current generated by the ohmmeter
resistance checks. is sufficient enough to forward-bias the diode.
Solenoids. A solenoid is an electrical compo-
nent. When electricity is applied to the coil, the Current Flow
solenoid will form an electromagnet. The magnet-
ic field will pull or push an armature into the coil
(based on application). The armature can be con-
nected to a switch in electrical circuits to turn the
switch on or off. An armature can also be used to
open or close valves.
Solenoids employed as electrical switches can be Cathode Anode
troubleshot with an ohmmeter. Remove the two
wires from the two larger posts of the solenoid.
Energize the solenoid. With an ohmmeter, check Illustration 6-10. Diode
the resistance between the two larger posts. The
ohmmeter should indicate between 0 - 40 ohms
nominally.
Solenoids employed as hydraulic switches are
used to open and close spools of valves. The
simplest way to prove the solenoid coil good is to
energize the solenoid and then, with a metal
object, touch the nut that secures the coil to the
cartridge. The magnetic field generated when the
coil becomes an electromagnet will be significant
enough to pull the metal object to the nut (some
solenoids employ a metal nut encased in plastic
and will require removal in order to detect the
magnetic field). This will prove the coil good; how-
ever, the armature may be stuck. If the hydraulic
circuit is still defective at this point, remove the coil
and cartridge. Now energize the coil, the arma-
ture inside the cartridge should shift. If the arma-
ture inside the cartridge did not shift and the coil is
magnetized, replace the cartridge.
6-10 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Refer to Illustration 6-15 for component reference
Component Problem Correction
1. Battery 1. Low voltage. 1.

a. Low electrolyte level. Check
electrolyte level in battery, fill
with distilled water as required,
and recharge battery.
b. Alternator output is bad. Refer
to the Alternator troubleshoot-
ing section below.
c. Loose, broken, or corroded
wires. Repair or replace wires.
d. Ensure that low voltage condi-
tion has not been caused by
accessories having been left
on for extended periods of
time.
2. Alternator 1. Low output voltage (voltage is 1.

below 12 VDC).
a. Ensure drive belts are tight.
b. Inspect the wiring for defects.
Check all connections for tight-
ness and cleanliness, includ-
ing the slip connectors at the
alternator and connections at
the battery.
c. Defective alternator. Replace
alternator.
2. High output voltage (voltage 2. Defective alternator. Replace
exceeds 15.5 VDC). alternator.
3. Battery Disconnect 1. When key switch is in the ON 1. Remove wires from the switch,
Switch position, contact points of switch turn the switch on. With an ohm-
do not close. meter, check the resistance across
the contact points. The ohmmeter
reading should indicate 0 - 40
ohms.
2. When key switch is in the OFF 2. Remove wires from the switch,
position, contact points of switch turn the switch off. With an ohm-
do not open. meter, check the resistance across
contact points. The ohmmeter
reading should indicate infinity.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 6-11
4. Ignition Switch 1. Ignition switch (S1) does not close 1. On the back of the ignition switch
(accessory position). (S1), at the B terminal, check for
12 VDC from circuit breaker
(CB2). Ensure that the battery
disconnect switch (S54, Illustration
1-6) is in the On position. If 12
VDC is not present, ensure that
circuit breaker (CB2) is set.
Ensure that Deutsch connector
(EC1) is not loose or that pin 6 or
11 is backed out of this connector.
Ensure that all battery cables are
connected to the terminals of the
batteries. Ensure that the batter-
ies are charged. Ensure that cir-
cuit breaker (CB1) can maintain a
set state. If 12 VDC is present at
the B terminal, turn the key to the
ignition position, at the I terminal,
you should see 12 VDC; if not,
remove the wire from the I termi-
nal and recheck voltage. If 12
VDC is now present, there is a
short between the ignition switch
(S1) and the truck power solenoid
(L1); isolate and repair short. If 12
VDC is not present and 12 VDC
was present at the B terminal,
replace the ignition switch (S1).
2. Ignition switch (S1) does not close 2. The truck is equipped with an anti-
(start position). restart ignition switch (S1).
Should the truck fail to start on the
first attempt, the key must be
turned fully off to reset the ignition
switch, allowing the B (Battery)
and S (Start) contacts to close
when the ignition switch is turned
to the Start position. This is a
momentary position that should
only make contact when the key is
fully turned. On the back of the
ignition switch (S1), ensure that 12
VDC is present at the B terminal.
If 12 VDC is not present, ensure
that circuit breaker (CB2) is set.
Ensure that Deutsch connector
(EC1) is not loose or that pin 7 is
backed out of this connector.
continued Ensure that all battery cables are
(continued)
6-12 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

4. Ignition Switch (Continued)

(Continued) connected to the terminals of the
batteries. Ensure that the batter-
ies are charged. Ensure that cir-
cuit breaker (CB1) can maintain a
set state. If 12 VDC is present,
turn the ignition switch (S1) to the
Start position. Check the S termi-
nal of the ignition switch for 12
VDC. If not present, remove the
wire from the S terminal; turn the
ignition switch to the Start position
and check for 12 VDC at the S ter-
minal. If 12 VDC is present, the
ignition switch is good.
5. Wires 1. Wire has lost continuity. 1. Isolate the wire from the circuit
(ohm out the wire). Ohms will vary
according to the length of the wire.
Expect to see low ohms if wire is
good.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 6-13

Electrical System Troubleshooting gauge indicates above 75 psi, remove wire #31
from the low air pressure switch (S13). If the low
Some of the components described in this section
air light (DS7) does not go out, wire #31 is shorted
are optional equipment.
out.
Eng Oil light (DS1, Illustration 6-15). The engine
Brake Fault light (DS8, Illustration 6-15) (if
oil light will illuminate when engine oil pressure
equipped). There are three signals in parallel
switch (S17, Illustration 1-6) has closed. The
capable of illuminating the brake fault light (DS8).
engine oil pressure switch will close between 7 -
10 psi on falling engine oil pressure. It is imperative that the technician understand how
these switches work to isolate the source of the
Battery light (DS3, Illustration 6-15). When the
failure. The simplest way to troubleshoot is to
battery light illuminates, it lets the operator know
remove the signal wire #32 from the switches
that there is a problem with the alternator. Refer
(S23, S24, and S27), one switch at a time. Start
to the Component Troubleshooting of the Alter-
the engine and see if the brake fault light (DS8) is
nator found earlier in this section.
illuminated. By removing the signal wire #32 from
Seat Belt light (DS4, Illustration 6-15). The seat the switch (S23, S24, or S27), the switch will be
belt light (DS4) will only illuminate when the key is eliminated from the circuit. Once the defective
in the ignition position and the seat belt is unfas- circuit has been removed, the brake fault light
tened. With the seat belt fastened, the seat belt (DS8) will not illuminate. Next, the technician
switch (S18) will send a ground through wire #38, must determine if the switch is bad or if the circuit,
energizing the seat belt relay (K2) and breaking the switch (S23, S24, or S27) is monitoring, is at
the contact between pins #30 and #87A of relay fault.
(K2), removing the ground from the seat belt light
Troubleshoot the switches (S23, S24, and S27) as
(DS4).
follows:
Shift Fail light (DS6, Illustration 6-15, if equipped
1. The power cluster overstroke indicator switch
with APC 70). The shift fail light (DS6) is con-
(S27) is located on the end cover between the
trolled by the APC 70 and will illuminate only when
shell assembly and the tube cylinder of the
the operator has attempted an improper shifting
power cluster. The overstroke indicator switch
procedure. The only purpose of this light is to let
is a normally open switch. A visual inspection
the operator know that he or she is outside of the
of the switch will confirm overstroke condition.
operating parameters.
The brass colored indicator rod will be protrud-
Low Air light (DS7, Illustration 6-15). The low air ing from the end cover approximately 3/4” to
light (DS7) will illuminate when the air pressure 1”. The indicator rod must be physically
falls below 75 psi. The low air pressure switch reseated. The most common cause of the
(S13), a normally closed switch, will close when brake fault light (DS8) illuminating is when an
the air pressure drops below 75 psi, sending overstroke condition has occurred.
ground through wire #31 (Illustration 6-15) com-
2. The brake coolant temperature switch (S24,
pleting the circuit to the low air light (DS7). In
Illustration 6-15) is located in the brake cooling
addition to the low air light being illuminated, an
valve. The brake coolant temperature switch
audible alarm will be heard from the low air / shut
is a normally open switch that will close at
down buzzer (LS5). When the air pressure drops
190_F. The simplest way to check this switch
to 60 psi, the parking brake valve will pop out,
is to turn the truck off and allow the truck to
applying the parking brake, closing the parking
cool. With an ohmmeter, measure the resist-
brake switch (S11). As a result, this will energize
ance between the posts on the switch and the
the brake saver relays (K23 and K31, Illustration
chassis ground. The ohmmeter reading
9C-2), taking away the 12 VDC signal from the
should indicate infinity (open circuit). If the
forward and reverse solenoids of the control valve
ohmmeter reading indicates a short, then the
that is located on the transmission. This inhibits
brake coolant temperature switch (S24) must
the operator from driving through the brakes. The
be replaced. Care must be taken to insure
air pressure gauge in the instrument panel will
that a good chassis ground is obtained.
assist in determining if the low air switch (S13) is
defective, if a short exists on wire #31, or if a low 3. The brake coolant pressure switch (S23,
air pressure problem exists. If the air pressure Illustration 6-15) is located in the brake man-
6-14 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
ifold valve. The brake coolant pressure switch wire when the wiper switch (S7) is in the Park
is a normally closed switch that will open at position.
10 psi. The purpose of this switch is to moni-
Top and Rear Wiper Circuits (Illustration 6-15).
tor for a low pressure problem in the brake
The top and rear wiper circuits are comprised of a
cooling circuit. When the pressure drops
circuit breakers (CB3 and CB24), wiper switches
below 10 psi, the switch will then close com-
(S8 and S9) and wiper motors (B8 and B9). 12
pleting the electrical circuit to the brake fault
VDC power is supplied from circuit breaker (CB3)
light (DS8). It must now be determined if the
to the B (Battery) post of the wiper switch (S8)
switch (S23) is defective or if a low pressure
while 12 VDC power is supplied from circuit break-
problem exists in the brake cooling circuit.
er (CB24) to the B (Battery) post of the wiper
There is a pressure test coupling (pressure
switch (S9). There are 6 posts on the back of the
check) located on the brake cooling manifold
wiper switches (S8 and S9). Post #5 (Park) of the
at port A. Plug a pressure gauge into the test
wiper switches are used for parking the wiper
port and with the engine running, observe the
motor (B9 and B8). When the wiper switches are
gauge reading. The maximum pressure
turned off, 12 VDC will be present at the post #5.
observed should be no more than 600 psi (the
When the wiper switches are turned on, 12 VDC
pressure will be between 0 and 600 psi).
will be present at post #1 (Low) or post #2 (High)
Remember it takes 10 psi to open the switch.
post of the wiper switches, contingent on the
If the pressure indicated is above 10 psi, the
speed selected. 12 VDC will be present at the W
brake coolant pressure switch (S23) is defec-
(Washer) post of the wiper switches (S8 or S9)
tive and must be replaced.
when the wiper switch is depressed. With the wip-
If all three of the switches, described above, have er switch (S8 or S9) turned off, 12 VDC is applied
been proven to be good and the brake fault light is at the P terminal of the wiper motor (B9 or B8) to
still illuminated, there is a short on the signal wire drive the wiper motor to the Park position. With
#32. Isolate and remove the short. the wiper switch (S8 or S9) in the Low position, 12
VDC is applied to the L terminal of the wiper motor
Front Wiper Circuit (Illustration 6-15). The front
(B9 or B8) for low speed. With the wiper switch
wiper circuit is comprised of a circuit breaker
(S8 or S9) in the high speed position, 12 VDC is
(CB4), wiper switch (S7) and wiper motor (B1). 12
applied to the H terminal of the wiper motor (B9 or
VDC power is supplied from circuit breaker (CB4)
B8) for high speed. The wiper motors (B9 and B8)
to the B (Battery) posts of the wiper switch (S7).
utilize chassis ground.
There are 6 posts on the back of the wiper switch
(S7). The P (Park) post of the wiper switch is Defroster Fan Motors (B2 and B4, Illustration
used for parking the wiper motor (B1). When the 6-15). The front defroster (B2) and the rear
wiper switch is turned off, 12 VDC will be present defroster (B4) fan motors are controlled by
at the P post. When the wiper switch is turned on, defroster switch (S6). Defroster switch (S6) is
12 VDC will be present at the L (Low) and H powered by circuit breaker (CB9). There is a
(High) posts of the wiper switch. 12 VDC will be diode between circuit breaker (CB9) and defroster
present at the W (Washer) post of the wiper switch switch (S6). Its purpose is to prevent an induced
(S7) when the wiper switch is depressed. Five voltage generated by the defroster fan motors (B2
wires are used on the wiper motor (B1). The and B4), which could prolong engine shut down,
black wire of the wiper motor is used for ground. after the ignition switch (S1) is turned to the Off
The blue wire of the wiper motor (B1) is is used for position. With the defroster switch (S6) in the Low
high speed. The yellow wire of the wiper motor position, 12 VDC will be present on wire #40A for
(B1) has a constant 12 VDC supply to it at all the front defroster motor (B2) or on wire #40 for
times while the key is at the accessory position. the rear defroster motor (B4). With the defroster
The red wire of the wiper motor (B1) is used for switch (S6) in the High position, 12 VDC will be
low speed. In this application, 12 VDC will be present on wire #41A for the front defroster motor
applied to the red wire when the wiper switch (S7) (B2) or wire #41 for the rear defroster motor (B4).
is in the Low position. The green wire of the wiper Both defroster motors (B2 and B4) utilize chassis
motor (B1) is used to drive the wiper motor to the ground.
Park position when the wiper switch (S7) is turned
Heater Fan Motor (B5, Illustration 6-15). The
off. There will be 12 VDC present on the green
heater fan motor (B5) is controlled by heater
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 6-15
switch (S5). Heater switch (S5) is powered by cir- tion, the contacts of the switch are closed. When
cuit breaker (CB8). There is a diode between cir- the forward alarm mode key switch (S14) is off
cuit breaker (CB8) and heater switch (S5). Its pur- (Operator Controlled Mode), the contacts of the
pose is to prevent an induced voltage generated switch are open. With the forward alarm mode
by the heater fan motor (B5), which could prolong key switch (S14) turned to the Automatic Position,
engine shut down, after the ignition switch (S1) is the forward alarm (LS4) will always be energized,
turned to the Off position. With the heater switch sounding an audible alarm any time the shifter is
(S5) in the Low / High position, 12 VDC will be placed in the forward position. With the forward
present on wire #43 to the heater fan motor (B5) alarm override switch (S14) turned to the Operator
for low speed operation. With the heater switch Controlled position, the forward alarm toggle
(S5) in the High position, 12 VDC will be present switch (S10) can activate the forward alarm circuit
on wire #44 to the heater fan motor (B5) for high when the shifter is in the forward position. This
speed operation. The heater fan motor (B5) is allows the operator to determine when or when
connected to the chassis ground by wire #11. The not to use the forward alarm circuit. With the shift-
heater fan motor (B5) will circulate air through a er in the forward position, 12 VDC is sent on wire
heater coil (which is heated by the engine coolant) #306 to pin 14 of forward relay (K17). Ground to
and into the cab. energize K17 is supplied by either S10 or S14. 12
VDC is supplied by circuit breaker (CB19) at all
Air Conditioner / Heater Unit (B7, Illustration
times to pin 9 (common pin) of K17. When K17
6-15). The air conditioner / heater unit (B7) is
energizes, the 12 VDC at pin 9 will pass out pin 5
powered by circuit breaker (CB16). Two power
to LS4 (forward alarm unit), energizing it.
wires #72 are sent from the circuit breaker (CB16)
to the air conditioner / heater unit (B7). This is
required to deliver the sufficient amperage to the
See the information in the
air conditioner / heater. All controls to the air con- Operator’s Guide and Safety Check concerning
ditioner / heater unit (B7) are internal to the air selecting the appropriate mode of operation.
conditioner / heater unit (refer to Section 20A for
additional information on the air conditioner / heat- Reverse Alarm (LS3, Illustration 6-15). The
er unit). reverse alarm circuit is designed to emit an audi-
Forward Alarm (LS4, Illustrations 6-16, 9C-2, and ble alarm when the shifter is in the reverse posi-
29-30). The forward alarm circuit is designed to tion. The reverse alarm circuit is controlled by the
emit an audible alarm when the shifter is in the shifter. With the shifter in the reverse position,
forward position and the forward alarm circuit has relay (K18) is energized. Circuit breaker (CB15)
been activated. The forward alarm circuit is con- will supply 12 VDC to pin #30 of relay (K18).
trolled by two switches, the forward alarm key When relay (K18) energizes, the 12 VDC present
switch (S14) and the forward alarm toggle switch at pin #30 will pass out pin #87 through wire #39,
(S10). The forward alarm mode key switch (S14) energizing the reverse alarm (LS3). Any time 12
is an on and off switch. When the forward alarm VDC is present on wire #319 at relay (K18), pin
mode key switch (S14) is in the Automatic Posi- #86, the reverse alarm (LS3) should be energized.
Refer to Illustration 6-16 for component reference
1. Eng Oil light (DS1) 1. Engine oil pressure is below 7 - 10 1. Refer to Problem 36. in the
is illuminated. psi. Engine Troubleshooting chart in
Section 1.
2. Defective engine oil pressure 2. Replace engine oil pressure
switch (S17). switch (S17).
3. There is a short on wire #4. 3. Isolate and repair short.
6-16 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
2. Battery light (DS3) is 1. Charge indicator relay (K3) is 1. Replace charge indicator relay
illuminated. defective. (K3). Refer to Alternator of the
Component Troubleshooting.
2. Defective alternator. 2. Replace alternator.
3. There is a short on wire #34. 3. Isolate and repair wire.
4. Wire #5 is open or shorted. 4. Isolate and repair wire.
3. Seat Belt light (DS4) 1. Seat belt is unfastened. 1. Fasten seat belt.
is illuminated.
4. Seat Belt light (DS4) 1. Seat belt relay (K2) is defective. 1. Refer to the Component Trouble-
is illuminated with shooting found earlier in this sec-
the seat belt fas- tion.
tened.
2. Wire #35 from Seat Belt light 2. Isolate and repair short.
(DS4) to seat belt relay (K2) has a
short on it.
3. Wire #38 from the seat belt switch 3. Isolate and repair.
(S18) is open.
4. Defective seat belt switch (S18). 4. Replace seat belt.
5. Shift Fail light (DS6) 1. Shift request is outside of shifting 1. Operate truck correctly (refer to
is illuminated. parameters. the Operator’s Guide for proper
(if equipped with shifting operations).
APC-70)
6. Low Air light (DS7) 1. Air pressure is below 75 psi. 1. Locate and repair leak (check all
is illuminated and fittings, hoses, seals, air tank, ser-
buzzer (LS5) is vice brake valve, de-clutch valve
energized. and brake actuators).
2. Wire #31 is shorted between the 2. Isolate and repair short. A good
low air pressure switch (S13) and indication of this problem will be
Low Air light (DS7). the air pressure gauge on the
instrument panel shows good air
pressure.
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.7/05)
06/03) 6-17
9. Low Air light (DS7) 3. Defective low air pressure switch 3. Allow truck to build air pressure,
is illuminated and (S13). shut down engine, and with an
buzzer (LS5) is ohmmeter read across each termi-
energized. nal of the low air pressure switch
(Continued) (S13) to chassis ground. Ohmme-
ter readings on one terminal
should be 0 - 40 ohms while the
other terminal’s ohmmeter reading
should be infinity. If the air pres-
sure gauge, located on the instru-
ment panel, shows good air pres-
sure and the ohmmeter readings
are not as described above,
replace low air pressure switch
(S13).
7. Brake Fault light 1. Overstroke indicator switch (S27) 1. Visually inspect the overstroke
(DS8) is illuminated is overstroked. indicator switch (S27). If an over-
stroked condition has occurred, a
brass colored indicator rod will be
protruding from the end cover of
the power cluster approximately
3/4” to 1”. To reset, push the indi-
cator rod back into the end cover.
2. Brake coolant pressure switch 2. Refer to the Electrical System
(S23) is defective. Troubleshooting of the Brake
Fault light found earlier in this
section.
3. Brake coolant pressure is below 3.
10 psi.
a. Leak in brake cooling circuit. a. Isolate leak and repair.
b. Defective pressure relief valve b. Replace the 175 psi pressure
in port 3 of the brake manifold relief valve in the brake man-
valve. ifold valve at port 3.
4. Brake coolant temperature switch 4. Refer to the Electrical System
(S24) is defective. Troubleshooting of the Brake
Fault light found earlier in this
section.
5. Brake coolant temperature 5. Refer to Problem 1. in the Wet
exceeds 190_F. Disc Brakes Cooling System
Troubleshooting chart in Section
15C.
6. There is a short on wire #32. 6. Isolate and repair
6-18 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

8. Left turn lamp (DS9) 1. The left turn lamp (internal to DS9) 1. Replace left turn lamp bulb.
will not illuminate is burned out.
when the turn signal
2. Circuit breaker is tripped (this will 2. Reset circuit breaker.
is activated for a left
turn affect DS11 as well).
(if equipped) 3. Defective flasher (this will affect 3. Replace flasher.
DS11 as well).
4. Defective turn switch (left side). 4. Replace turn switch.
The turn switch is mounted on the
steering column.
5. Loose or broken wire. 5. Check all connections or repair
wire.
9. Park Brake light 1. Parking brake is applied. 1. Release parking brake.

(DS10) is illumi-
2. Park brake switch (S11) is defec- 2. Replace park brake switch (S11).
nated
tive.
3. Air pressure is below 60 psi. 3. Refer to Problem 3. in the Brake
Control System Troubleshoot-
ing chart in Section 15.
10. Right turn lamp 1. The right turn lamp (internal to 1. Replace right turn lamp bulb.
(DS11) will not illu- DS11) is burned out.
minate when the
2. Circuit breaker is tripped (this will 2. Reset circuit breaker.
turn signal is acti-
vated for a right turn affect DS9 as well).
(if equipped) 3. Defective flasher (this will affect 3. Replace flasher.
DS9 as well).
4. Defective turn switch (right side). 4. Replace turn switch.
The turn switch is mounted on the
steering column.
5. Loose or broken wire. 5. Check all connections and repair
wire if necessary.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 6-19

6-20 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)
Illustration 6-11. Truck Layout Wiring Diagram
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 6-21
6-22 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
5/05)
06-2447 SHT. 03
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 6-23
Hoist Circuit
6-24 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 6-12. Main Control Junction Box
06-2447 SHT. 06
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 6-25
Illustration 6-13. Cab Rear Panel Harness
I-1-29-1056
6-26 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
5/05)
Hoist Circuit

FOLDER ENVELOPES:
Illustration 6-14 - 06 2447 SHT. 10 (Truck Control ANSI)
Illustration 6-15 - 06 2447 SHT. 9 (ANSI)
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.5/05)
06/03) 6-27
Hoist Circuit
6-28 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

6A-Closed Circuit Cameras and Monitors
Section 6A
Closed Circuit TV Camera and Monitor

Introduction. The reverse camera system (if depress the switch to reduce the picture
equipped) gives the operator a vantage view from brightness (Night).
a remote mounted camera, strategically placed,
5. Contrast Control Knob. Use this knob to
dependant on operational requirements.
adjust the screen’s contrast. Turn the knob
clockwise to increase picture contrast and
counterclockwise to decrease.
6. Brightness Control Knob. Use this knob to
adjust the screen’s brightness. Turn the knob
clockwise to increase picture brightness and
counterclockwise to decrease.
7. Volume Control Knob. Use this knob to
adjust the sound level of the monitor if
equipped with audio function (not used on
Taylor trucks).
Major Components. The camera circuit consists Front View of Camera

of a camera, monitor, and connecting video
cables.
Camera (Illustration 6A-1). The camera sends
imagery to the monitor. The camera must be kept
clean (lens) and in proper operating order.
NOTE: The camera’s left to right orientation is
controlled by the two screws (A and B), located on Back View of Camera
the back of the camera. Do Not switch the place-
ment of these two screws.
Position A - Silver Screw (short)
Position B - Black Screw (long)
Monitor (Illustration 6A-2). The monitor displays
imagery from the camera for the operator’s view-
ing. A B
Monitor Operation. The following describes the
monitor’s controls. Illustration 6A-1. Camera
1. Power Switch. Press this switch to turn the
monitor on (green LED will illuminate). Press
this switch again to turn the monitor off.
1
2. Camera Audio / Video Selector Switch.
Depress this switch (out position) to select the 2
camera mode with the camera selector switch. 3
Press this switch to select the AV input signal 4
(not used on Taylor trucks).
5
3. Camera Selector Switch. Depress this 6
switch (out position) to select the forward cam-
era view (CA1). Press this switch to select the 7
reverse view camera (CA2).
4. Day / Night Switch. This switch should nor-
mally be in the out position (Day). When view- Illustration 6A-2. Monitor
ing the picture at night or in a tunnel, etc.,
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05) 6A-1
06/03)
Illustration 6A-3. Reverse Camera Circuit
06C-0051 SHT. 01
6A-2 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
3/05)
06/03)
6L-Auxiliary Lighting
Section 6L
Auxiliary Lighting
Introduction. The high intensity discharge
(H.I.D.) lighting system, if equipped, provides the

user several times the output of incandescent or S The H.I.D. lighting system operates under
halogen lamps, utilizing the same levels of input high voltage. Disconnect all input power to
energy. the ballast assembly before attempting any
service. Failure to observe this warning may
H.I.D. Lights (Illustration 6L-1). The lighting unit
result in personal injury or death.
is comprised of a bulb, ballast and a starter,
located in the ballast. The bulb contains a gas- S All electrical work should be performed only
eous environment and houses the arc. The start- by qualified service technicians.
ÍÍÍÍÍÍÍÍÍ
er will boost the voltage from the ballast, creating
ÍÍÍÍÍÍÍÍÍ
an arc inside the bulb. The ballast will then pro-
vide high voltage to maintain the arc. At initial
startup, the lighting unit can draw a maximum of
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
20 amps. Once the lighting unit has illuminated, it
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
can draw a maximum of 3.18 amps (steady state).
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
H.I.D. Lighting System Maintenance. The H.I.D.
lighting system is a long life, self-sustaining lamp
that requires little or no regular maintenance.
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
ÍÍÍÍÍÍÍÍÍ
Some operating environments, however, may
ÈÈÈÈÈÈÈÈ
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
require periodic cleaning of excess dirt or debris
from the lense, and periodic checks of the cables
and connections for signs of damage or wear. If
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
the H.I.D. lighting system fails to operate properly,
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
ÍÍÍÍÍÍÍÍÍ
ÈÈÈÈÈÈÈÈ
refer to the H.I.D. Lighting System Troubleshoot- BULB BALLAST
ing chart. (STARTER)
ÍÍÍÍÍÍÍÍÍ
ÍÍÍÍÍÍÍÍÍ
Illustration 6L-1. H.I.D. Work Lights
H.I.D. Lighting System Troubleshooting (Illustration 6L-1)
1. H.I.D. light does 1. Bulb burned out. 1. Disconnect power, replace bulb,
not illuminate reconnect power and check light
for illumination.
2. Blown fuse. 2. Check fuse and replace if neces-
sary.
3. Loose or broken wire. 3. Check electrical connections and
wire. Repair as required. Should
wire require replacing, replace with
a wire of the same gauge.
4. Defective ballast. 4. Disconnect power, replace ballast
assembly, reconnect power and
check light for illumination.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 6L-1

1-12 RTGP-9042N (9/01)
Section 9
Transmission
SPREADER / BRAKE
PUMP MAIN
CHARGING
PUMP PUMP
DIPSTICK
OIL SCREEN
BREATHER PLUG
OIL SCREEN
FULL
DRAIN PLUG
LOW
FLEX PLATE DE-CLUTCH VALVE
FILLER CAP
CONTROL
VALVE
Illustration 9-1. TC-36 Transmission

Introduction. The TC-36 transmission is a pow- The remaining oil is directed through the torque
ershift transmission which provides three speeds converter circuit to the oil cooler and returns to the
forward and three speeds reverse. Both direction transmission for positive lubrication. After enter-
and speed range are controlled by a roll shift ing the converter housing, the oil is directed
mechanism attached to the steering column. The through the stator support to the converter blade
transmission can be neutralized during braking by cavity and exits in the passage between the tur-
a de-clutch feature (refer to Section 15 for bine shaft and converter support. The oil then
de-clutch operation). flows out of the converter to the oil cooler. After
leaving the cooler, the oil is directed back to the
Operation. With the engine running, the trans-
transmission.
mission’s converter charging pump draws oil from
the transmission sump through the oil sump The torque converter turbine receives fluid at its
screen and directs it through the pressure regulat- center. The reaction member of the torque con-
ing valve and oil filter. The pressure regulating verter takes the fluid which is exhausting from the
valve maintains pressure to the transmission con- inner portion of the turbine and changes its direc-
trol valve for actuating the direction and speed tion to allow correct entry for recirculation into the
clutches. This requires only a small amount of oil. impeller element.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9-1

REVERSE Dispose of filters in accor-
dance with federal and local regulations.
2ND
NOTE: It is recommended that filter elements be
changed after 50 and 100 hours of operation on
1ST new and rebuilt or repaired transmissions.
1. Make certain filters are cool to the touch, then
FORWARD provide a suitable container to catch any
draining oil, and unscrew filter and dispose of
filter properly.
2. Apply an even film of fresh oil on the gasket
surface of the replacement filter elements.
Then thread each filter onto the filter head
assembly.
Illustration 9-2. Transmission Control Valve
3. Hand tighten each filter element 3/4 turn past
Transmission Control Valve (Illustration 9-2). point where gasket first contacts filter head
The transmission control valve directs oil, under surface.
pressure, to the desired directional and speed 4. Refer to Filling The Transmission for adding
clutch. The directional and speed clutch assem- oil to the transmission.
blies are mounted inside the transmission case
and are connected to the output shaft of the con-
verter either by direct gearing or drive shaft. The
purpose of the directional or speed clutches is to FILTER
direct the power flow through the gear train to pro- HEAD
vide the desired speed range. Refer to Section ASSEMBLY
9C for electrical operation of the transmission con-
trol valve.
Oil Level Check (Illustration 9-1). The oil level
should be checked daily, with the oil at normal
operating temperature (180_F to 200_F+) and the
engine operating at low idle. The oil level should
be up to the FULL mark on the dipstick. The dip-
stick is located inside the right engine hood door,
beside the filler cap. FILTER
ELEMENTS
Changing The Filter Elements (Illustration 9-3).
The oil filter elements, located on the left side of
the truck below the engine access door, should be
changed every 500 hours. The interval above is
based on normal environmental condition, exces-
sive dust may require a more frequent filter
change interval. Perform the following procedures
to change the filter elements: Illustration 9-3. Transmission Oil Filter Element
Changing The Oil (Illustration 9-1). The transmis-

Park machine on a level sur- sion oil should be changed every 1000 hours.
face, apply parking brake, block wheels and The oil should be drained with oil at a temperature
Lock Out & Tag Out while servicing machine. of 150_F to 200_F.
9-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

4. Reinstall the breather.

Park machine on a level sur-
General Information
face, apply parking brake, block wheels and
Lock Out & Tag Out while servicing machine. Oil Pressure (low idle) 240 psi
Oil Pressure (high idle) 310 psi
Dispose of oil and filter in Oil Temperature 180 - 250_F
accordance with federal and local regulations. (82.2 - 121_C)
Perform the following procedures to change the Oil Capacity 40 Quarts
transmission oil: Transmission Stall Speed 1990 rpm$50
1. Provide a suitable container and remove the rpm
drain plug to drain the oil.
2. Remove the oil screen and gasket.
3. Clean the oil screen thoroughly.
4. Use a new gasket and reinstall the oil screen.
Tighten the oil screen to 10 to 15 ft-lbs.
5. Refer to Changing The Filter Elements for
procedures to change the filter elements.
6. Reinstall the drain plug.
7. Refer to Filling The Transmission, located
below, for adding oil to the transmission.
Filling The Transmission (Illustration 9-1). Per-
form the following procedures to fill the transmis-
sion with oil:
1. With engine shut down, fill the transmission to
the FULL mark on the dipstick.
2. Operate the engine and check for leaks.
When the oil temperature reaches +180_F to
+200_F and the engine is operating at low
idle, make a final oil check and add oil to bring
the oil level to the FULL mark on the dipstick.
Cleaning The Transmission Breather (Illustra-
tion 9-1). The breather should be checked every
1500 hours of operation for restriction. The preva-
lence of dirt and dust will determine the frequency
at which the breather requires cleaning. Perform
the following procedures to clean the transmission
breather:
1. Clean the area around the breather before
removing it.
NOTE: Care must be exercised when removing
the breather to avoid damaging the breather.
2. Remove the breather.
3. Wash the breather thoroughly in solvent and
dry it with compressed air.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9-3

PORT AR
PORT S CHARGE CONVERTER IN
PUMP PRESSURE PRESSURE
240 - 310 PSI
PORT AQ CONVERTER
OUT TO COOLER
PORT R CONVERTER
OUT PRESSURE (25
PSI MIN. @ 2000 RPM - PORT J OIL COOLER
70 PSI MAX. @ RATED, TEMPERATURE
NO LOAD GOVERNED SWITCH (245°F N.C.)
RPM) LOCATION
PORT RC MODULATED
REVERSE CLUTCH
PRESSURE 240 - 310 PSI
PORT K
FULL OIL LEVEL *
PORT L
LOW OIL LEVEL *
PORT FC MODULATED
FORWARD CLUTCH
PRESSURE 240 - 310 PSI * OIL LEVEL SHOULD BE CHECKED AT
OPERATING TEMPERATURE WITH THE
TRANSMISSION IN THE NEUTRAL POSITION
Illustration 9-4. Transmission Check Points
9-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

PORT S
PORT H PORT AR
TRANSMISSION
OIL FILTERS
PORT AQ
PORT AD PORT J
PORT R
PORT AH
TRANSMISSION
OIL COOLER
INDICATES HYDRAULIC FLUID FLOW
Illustration 9-5. Transmission Fluid Flow
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9-5

Transmission Troubleshooting
Electrical / Mechanical Checks. Prior to check- 2. Work the machine to bring the oil temperature
ing any part of the system from a hydraulic stand- up to the operating range (refer to step 1.
point, the following electrical / mechanical checks above).
should be made.
NOTE: If the machine cannot be worked, the con-
1. Ensure that the proper solenoids on control verter can be stalled to bring the temperature up
valve are energized. When the solenoids are to the operating range. Perform the following pro-
energized they become magnetized. A mag- cedures to stall the converter.
netic field can be checked at the nut that holds
the solenoid to the cartridge. An effective way 3. With the right service brake pedal applied,
to accomplish this is with a metal wrench. move the shifter to the forward position and
Some solenoids employ a metal nut, encased third gear selected.
in plastic, which will require removal to detect
a magnetic field. 4. Continue to apply the brakes and accelerate
the engine approximately one-half to three-
2. Ensure that the de-clutch valve is not engaged quarter throttle for 30 seconds, let off accelera-
nor sticking. tor for 10 seconds.
Hydraulic Checks. Before checking the torque 5. Repeat step 4. until the desired converter out-
converter, transmission, and associated hydraulic let temperature is reached.
system for pressures and rate of flow, it is essen-
tial that the following preliminary checks be made.
Full throttle stall speeds for an
NOTE: Do not attempt these checks with cold oil. excessive length of time will overheat the
converter.
1. Check the oil level in the transmission. This
should be done with the oil temperature 6. When checking the pressures, always check
between +180°F and +200°F, and the engine the charge pump and converter out pressures
operating at idle. first.
1. Low Clutch Pres- 1. Low oil level. 1. Fill to proper level.

sure at Port S
2. Clutch pressure regulating valve 2. Clean valve spool and housing.
(Also Port RC in
spool stuck open.
Reverse and Port
FC in Forward; all 3. Defective charging pump (240 - 3. Replace pump.
three must be 310 psi normal operating
checked in order to pressure).
diagnose problem).
Refer to Illustration 4. Broken or worn clutch shaft or pis- 4. Replace sealing rings or clutch
9-4 for port loca- ton sealing rings. shaft.
tions. 5. Clutch piston bleed valve stuck 5. Clean bleed valves thoroughly.
open.
2. Low Converter 1. Low oil level. 1. Fill to proper level.

Charging Pump
Output at Port S 2. Suction screen plugged. 2. Clean suction screen.
(refer to Illustration 3. Air leaks at pump intake hose and 3. Tighten all connections or replace
9-4 for port loca- connections or collapsed hose. hose if necessary.
tions)
4. Defective oil pump. 4. Replace pump.
continued
9-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

2. Low Converter 5. Clogged transmission filters. 5. Replace transmission filters.

Charging Pump
Output at Port S 6. Defective pressure regulator. 6. Replace or rebuild pressure
(refer to Illustration regulator.
9-4 for port loca-
tions) (Continued)
3. Noisy Converter 1. Worn coupling gears. 1. Replace coupling gears.

2. Worn oil pump. 2. Replace oil pump.
3. Worn or damaged bearings. 3. A complete disassembly will be
necessary to determine which
bearing is faulty.
4. Low charge pump pressure. 4. Refer to Problem 2. of this trouble-
shooting chart.
5. Excessive internal leakage in con- 5. Rebuild or replace transmission.
verter.
4. Overheating 1. Low oil level. 1. Fill to proper level.

2. Oil cooler vents are restricted. 2. Clean oil cooler.
3. Worn transmission bearing. 3. Replace or rebuild transmission.
4. Worn oil sealing rings. 4. Remove, disassemble and rebuild
converter assembly.
6. Pump suction line taking air. 6. Check connections, tighten
securely.
7. Open circuit between the engine 7. Isolate and repair.
ECM (Electronic Control Module)
and transmission temperature
sender.
8. Defective transmission tempera- 8. Replace transmission temperature
ture sender. sender.
5. Lack of Power 1. Low engine RPM at converter 1. Tune engine and check governor.
stall.
2. Worn oil sealing rings. 2. Remove, disassemble and rebuild
converter assembly.
4. Low oil level. 4. Fill to proper level.
5. Restriction in hydraulic circuit. 5. Remove restriction.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9-7

6. No Forward 1. Defective shifter circuit. 1. Perform electrical check to ensure

electrical signal has energized
solenoid. Refer to the Testing of
Electrical Components proce-
dures in Section 9C.
2. Defective brake saver relay (K31, 2. Refer to the Testing of Electrical
Illustration 9C-2) or circuit. Components procedures in
Section 9C to troubleshoot circuit.
3. Defective solenoid or cartridge in 3. Swap the Forward and Reverse
control valve. cartridges and solenoids; if the
fault changes from Forward to
Reverse, the solenoid or cartridge
is bad. To determine which is bad,
switch the solenoids only. If the
fault did change, replace the
defective solenoid. If fault did not
change, replace cartridge.
4. Reverse clutch pack plates are 4. Place the transmission in the neu-
fused together. tral position and rev up the
engine. If the truck tries to move
in reverse, clutch plates are fused
together. Replace or rebuild
transmission.
5. Defective regulators in the modu- 5. Replace the modulator valve.
lator valve.
6. Spools are sticking in control valve 6. Clean or replace defective parts.
body.
7. No Reverse 1. Defective shifter circuit. 1. Perform electrical check to ensure

electrical signal has energized
solenoid. Refer to the Testing of
Electrical Components proce-
dures in Section 9C.
2. Defective brake saver relay (K23, 2. Refer to the Testing of Electrical
Illustration 9C-2) or circuit. Components procedures in
Section 9C to troubleshoot circuit.
3. Defective solenoid or cartridge in 3. Swap the Forward and Reverse
control valve. cartridges and solenoids; if the
fault changes from Reverse to
Forward, the solenoid or cartridge
is bad. To determine which is bad,
switch the solenoids only. If the
fault did change, replace the
defective solenoid. If fault did not
change, replace cartridge.
continued
9-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

7. No Reverse 4. Forward clutch pack plates are 4. Place the transmission in the neu-
(Continued) fused together. tral position and rev up the
engine. If the truck tries to move
in forward, clutch plates are fused
together. Replace or rebuild
transmission.
5. Defective regulators in the modu- 5. Replace the modulator valve.
lator valve.
6. Spools are sticking in control valve 6. Clean or replace defective parts.
body.
8. No Forward or 1. Shifter or input to Shifter is bad. 1. Refer to the Testing of Electrical

Reverse Components procedures in
Section 9C.
2. Parking brake switch (S11, 2. Replace parking brake switch.
Illustration 9C-2) in parking brake
valve is bad.
3. 12 VDC power on Wire #29 3. Refer to Testing of Electrical
(Illustration 9C-2). Components in Section 9C.
4. De-clutch valve is stuck or 4. Disconnect the linkage from the
engaged. inching valve to ensure that inch-
ing valve is not engaged. Push
spool in and out to ensure that the
spool is not stuck.
5. Defective brake saver relays (K23 5. Replace brake saver relays (K23
and K31). and K31).
6. Low charge pump pressure. 6. Refer to Problem 2. of this trouble-
shooting chart.
7. Low converter out pressure. 7. Refer to Problem 2. of this trouble-
shooting chart.
8. Drive shaft in truck is missing. 8. Ensure that the drive shaft is
assembled to the transmission
and drive axle.
9. Vibration 1. Defective differential. 1. Repair differential.

2. Output shaft in transmission is 2. Repair or tighten output shaft.
loose.
3. Transmission mount is loose. 3. Repair or tighten transmission
mount.
4. Engine mount is loose. 4. Repair or tighten engine mount.
5. Excessive backlash in differential. 5. Repair differential.
continued
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9-9

9. Vibration 6. Plates inside transmission are 6. Repair or replace engine clutch

(Continued) sticking or slipping. wear or plates.
7. Defective de-clutch valve. 7. Replace de-clutch valve.
8. Defective torque converter. 8. Repair or replace converter.
9. Defective charge pump. 9. Repair or replace charge pump.
10. Drive shaft is out-of-phase. 10. Correct drive shaft to be in phase.
11. Loose or missing universal joints. 11. Tighten or replace.
12. Defective universal joints. 12. Replace universal joints.
13. Accessory pumps, located on the 13. Replace or tighten.
back of the transmission, are cavi-
tating or loose.
14. Low hydraulic oil in transmission. 14. Add hydraulic oil to the recom-
mended level.
15. Transmission is overheating. 15. Troubleshoot and repair transmis-
sion.
16. Drive axle loose. 16. Tighten and re-torque drive axle.
17. Tread pattern on tires. 17. Change tread pattern.
9-10 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

9A-Transmission Cooler
Section 9A
Transmission Cooler
PORT AQ
PORT AH
TRANSMISSION
OIL COOLER
COOLER INLET
PRESSURE HOSE COOLER OUTLET
PRESSURE HOSE
Illustration 9A-1. Transmission Oil Cooler Hose Flow Diagram

Introduction. The transmission oil cooler Whenever the cooler hoses have been discon-
employs a forced air cooled method of cooling the nected and then reconnected, operate the engine
transmission oil. up to normal operating temperature and check the
transmission oil cooler hoses connections for
Transmission Oil Cooler Maintenance. The
leaks.
transmission oil cooler should be cleaned exter-
nally as conditions warrant.
Make certain used filter and
drained oil are disposed of in accordance with
In the event of transmission
failure requiring a new or rebuilt transmission,
in order for warranty to be valid, the transmis-
sion oil cooler, transmission filter, and hoses
from the transmission to the transmission oil
cooler must be replaced. It is impossible to
back flush the transmission oil cooler to
remove all contaminants from the core.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05) 9A-1
06/03)
9A-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev.
06/03)
9C-Transmission Controls
Section 9C
Transmission Controls (Electric Shift)

bad or is not fully in the accessory position.
d. Circuit breaker (CB1, see Illustration 1-6),
located in the engine compartment, is
tripped or bad.
e. A loose or broken wire between any of the
above components.
5. Troubleshoot the circuit breakers by referring
to the Components Troubleshooting of the
Circuit Breakers in Section 6.
6. If 12 VDC power is present, proceed with the
following procedures (see Illustrations 9C-2
and 9-2).
a. With shifter in Forward First Gear, find the
control valve located on transmission.
Illustration 9C-1. Electric Shifter Three solenoids will be energized if shifter
is functioning properly. Touch the nut
Introduction. This truck utilizes an electrically located at the top of the solenoid with a
operated transmission shifting system; therefore, metal object. The metal object will be
no mechanical linkage is needed. The following pulled toward the solenoid due to a mag-
procedures are to be used to test the transmission netic field that will be present if the sole-
controls. If service becomes necessary, refer to noid is energized. Some solenoids employ
the following electrical components testing proce- a metal nut, encased in plastic, which will
dures. require removal to detect a magnetic field.
Exercise care not to reverse the polarity of
the solenoid because the solenoid con-

Before servicing truck, park tains internal diodes which will be
the truck on level ground and block the destroyed if the polarity of the solenoid is
wheels. reversed. Two signals are required to
energize the Forward solenoid: 12 VDC
Testing of Electrical Components from the electric shifter, through the for-
1. Turn ignition switch to the “Accessory” posi- ward brake saver relay and ground. If the
tion. Forward solenoid did not energize, it must
be determined if one of the signals is miss-
2. Ensure that the parking brake is not applied. ing or if the coil is bad.
3. Check for 12 VDC power input to shifter
NOTE: Earlier model trucks broke the ground
at the plug located underneath the instrument
through the brake saver relays to the solenoids of
panel, near steer column, input pin 1.
the transmission control valve. It is important that
NOTE: If unable to locate input power to the shift- the technician consider this possibility when trou-
er, the truck will not start. bleshooting the electric shift forward and reverse
circuits.
4. Troubleshoot, as follows, to find the source of
shifter input power failure: b. Unplug the weatherpack connector of the
Forward solenoid. With a trouble light
a. Circuit breaker (CB10 or CB2, Illustration grounded to the chassis, make contact
9C-2, 6-16), located in the instrument pan- with the hot wire of the weatherpack on the
el, is tripped or bad. shifter side. Light will illuminate if there is
b. Truck power solenoid (L1, see Illustration a good ground through the trouble light
1-6) failed to energize or is bad. and 12 VDC is present. If trouble light fails
to illuminate, troubleshoot the circuit back
c. Ignition switch (S1, see Illustration 6-16) is
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-1

towards the shifter. If 12 VDC is present, bleshooting the electric shift forward and reverse
continue to troubleshoot as follows. circuits.
c. Re-connect the weatherpack connector a. Unplug the weatherpack connector of the
and make contact with the ground side of Reverse solenoid. With a trouble light
the Forward solenoid with the trouble light. grounded to the chassis, make contact
Light should not illuminate. If it does illumi- with the hot wire of the weatherpack on the
nate, ground to the coil is missing. shifter side. Light will illuminate if there is
d. If 12 VDC plus ground is present at the a good ground through the trouble light
solenoid and it does not energize, the sole- and 12 VDC is present. If trouble light fails
noid is bad and needs replacing. to illuminate, troubleshoot the circuit back
towards the shifter. If 12 VDC is present,
7. The energized solenoids for Forward First continue to troubleshoot as follows.
Gear are Forward, First, and Second.
b. Reconnect the weatherpack connector and
8. If all three of the solenoids are energized, make contact with the ground side of the
place the shifter in Forward Second and Reverse solenoid with the trouble light.
repeat procedure 6. again for Forward Light should not illuminate. If it does illumi-
Second. nate, ground to the coil is missing.
NOTE: Electrical operation of all the solenoids is c. If 12 VDC plus ground is present at the
easily confirmed when the magnetic field is solenoid and it does not energize, the sole-
detected by touching the nut that secures the coil noid is bad and needs replacing.
to the cartridge of the desired solenoid.
13. With the shifter in Neutral and Third Gear
9. The energized solenoids are Forward and selected, ensure that there are no energized
Second. solenoids at this point.
10. If all solenoids are energized, place the shifter 14. If shifting failure is still experienced, the prob-
in Forward Third and repeat procedure 6. lem is not electrical.
again for Forward Third.
11. The energized solenoid for Forward Third is
“Forward”. Only the Forward solenoid is ener-
gized because the highest gear selected will
always be spring applied and does not require
a solenoid operated spool to apply it.
12. If the solenoid energized, place the shifter in
Reverse. Check and ensure that the Reverse
solenoid is energized, and that the Forward
solenoid is NOT energized. There is no need
to check any of the gear select solenoids at
this point, they have been proven to be oper-
ating properly. Two signals are required to
energize the Reverse solenoid: 12 VDC from
the electric shifter through the reverse brake
saver relay and ground. If the Reverse sole-
noid did not energize, you must determine if
one of the signals is missing or if the coil is
bad.
NOTE: Earlier model trucks broke the ground
through the brake saver relays to the solenoids of
the transmission control valve. It is important that
the technician consider this possibility when trou-
9C-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Electric Shift Troubleshooting (Illustration 9C-2)
1. No Forward 1. Parking brake is applied. 1. Disengage parking brake.

2. Shifter to rear panel harness 2. Ensure that shifter to rear panel
plug (PC1) is loose or pin 2 is harness plug (PC1) has good con-
backed out of plug. nection and all pins are seated.
3. Weatherpack at control valve to the 3. Ensure weatherpack has good
forward solenoid is loose or pin is connection and all pins are seated.
backed out of weatherpack.
4. Panel harness connector (RPC1 or 4. Ensure panel harness connector
PC7) is loose or pin of connector is (RPC1 or PC7) has good connec-
backed out. tion and all pins are seated.
5. Faulty solenoid on the forward car- 5. Replace solenoid.
tridge located on the control valve.
6. Defective shifter. 6. Disconnect the shifter to rear panel
harness plug (PC1). Jumper pin 1
of plugs together. This jumper
allows input power (12 VDC) to the
shifter. Turn the ignition switch to
the accessory position. Shift the
shifter to the Forward position. On
the shifter side of the plug, check
for 12 VDC coming out of the shift-
er at pin 2. If 12 VDC is present,
the shifter is good.
7. Defective forward brake saver 7. Replace forward brake saver
relay (K31). relay (K31).
8. Shifter to rear panel harness 8. Isolate and repair wiring.
wire #312 (forward) is broken or
loose at the forward brake saver
relay (K31).
9. Forward brake saver relay (K31) to 9. Isolate and repair wiring.
terminal strip (located in rear panel
of cab) wire #352 is broken or
loose at the terminal strip.
10. Rear panel to main junction box 10. Isolate and repair wiring.
(located on the front of truck) har-
ness wire #306 (forward) is broken
or loose at the terminal strip in the
rear panel.
11. Transmission harness wire #306 11. Isolate and repair wiring.
(forward) is broken or loose at the
terminal strip in the main junction
box.
continued
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-3

1. No Forward 12. Transmission harness wire #311 12. Isolate and repair wiring.
(Continued) (forward solenoid, ground side) is
broken or loose at the terminal strip
in the main junction box.
2. No Reverse 1. Parking brake is applied. 1. Disengage parking brake.

2. Shifter to rear panel harness 2. Ensure that shifter to rear panel
plug (PC1) is loose or pin 5 is harness plug (PC1) has good con-
backed out of plug. nection and all pins are seated.
3. Weatherpack at control valve to the 3. Ensure weatherpack has good
reverse solenoid is loose or pin is connection and all pins are seated.
backed out of weatherpack.
4. Panel harness connector (RPC1 or 4. Ensure panel harness connector
PC7) is loose or pin of connector is (RPC1 or PC7) has good connec-
backed out. tion and all pins are seated.
5. Faulty solenoid on the reverse car- 5. Replace solenoid.
tridge located on the control valve.
the accessory position. Shift the
shifter to the Reverse position. On
the shifter side of the plug, check
for 12 VDC coming out of the shift-
er at pin 5. If 12 VDC is present,
7. Defective reverse brake saver 7. Replace reverse brake saver
relay (K23). relay (K23).
8. Shifter to rear panel harness 8. Isolate and repair wiring.
wire #319 (reverse) is broken or
loose at the reverse brake saver
relay (K23).
9. Reverse brake saver relay (K23) to 9. Isolate and repair wiring.
terminal strip (located in rear panel
of cab) wire #354 is broken or
loose at the terminal strip.
10. Rear panel to main junction 10. Isolate and repair wiring.
box (located on the front of truck)
harness wire #307 (reverse) is bro-
ken or loose at the terminal strip in
the rear panel.
continued
9C-4 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
2. No Reverse 11. Transmission harness wire #307 11. Isolate and repair wiring.
(Continued) (reverse) is broken or loose at the
terminal strip in the main junction
box.
12. Transmission harness wire #311 12. Isolate and repair wiring.
(reverse solenoid, ground side) is
broken or loose at terminal strip in
the main junction box.
3. No Forward or 1. Parking brake is applied. 1. Disengage parking brake.

Reverse
2. Shifter harness connector (PC1, 2. Ensure shifter harness connector
RPC1 or PC7) is loose or pins of (PC1, RPC1 or PC7) has good
connector are backed out. connection and all pins are seated.
3. Panel harness plug (RPC1 or PC7) 3. Ensure panel harness plug has
is loose at panel harness connec- good connection and all pins are
tion or pins of connector have seated.
backed out.
4. Defective park brake pressure 4. Replace park brake pressure
switch (S11). switch (S11) in parking brake.
Pressure switch (S11), if closed,
will send 12 VDC to the forward
and reverse brake saver relays
(K31 and K23), energizing both
relays, breaking the current path
from the shifter to the Forward and
Reverse solenoids. This is a valu-
able troubleshooting aid because it
affects both Forward and Reverse.
5. Forward and reverse brake saver 5. 12 VDC is present on wire #29
relays (K31 and K23) are ener- from park brake pressure switch
gized. (S11).
6. Defective shifter. 6. Replace shifter.
7. Circuit breaker (CB2 or CB10) is 7. Reset or replace circuit breaker.
tripped or defective.
8. Truck power solenoid (L1) is defec- 8. Replace truck power solenoid.
tive.
9. Defective ignition switch (S1). 9. Replace ignition switch.
10. Loose, broken, or shorted wires 10. Isolate and repair.
between any of the above compo-
nents.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 9C-5
4. Truck Stays in First 1. Defective shifter. 1. Disconnect the shifter to rear panel
Gear Only harness plug (PC1). Jumper pin 1
shifter. Turn the ignition to the
accessory position. Roll the shifter
to the First gear position. On the
shifter side of the plug, check for
12 VDC coming out of the shifter at
pins 3 and 4. If 12 VDC is present,
roll the shifter to 2nd gear position.
12 VDC will no longer be present
on pin 3, 12 VDC will be present on
pin 4. If these checks are good,
2. Shifter to rear panel harness wire 2. Isolate and remove the 12 VDC.
#314 (first gear) has 12 VDC on it
all the time.
3. Rear panel to main junction box 3. Isolate and remove the 12 VDC.
wire #304 (first gear) has 12 VDC
on it at all times.
5. Truck Stays in 1. Shifter to rear panel harness con- 1. Ensure that shifter to rear panel
Third Gear Only nector (PC1) is loose or pins 3 and harness connector (PC1) has good
4 of connector are backed out. connection and all pins are seated.
2. The ground wires #311 for the first 2. Reseat the wires at the terminal
and second gear solenoids are not strip.
properly grounded to the terminal
strip.
3. Rear panel to main junction box 3. Isolate and repair wires.
harness wire #304 (first gear) and
wire #305 (second gear) have
been cut or broken.
4. Main junction box to transmission 4. Isolate and repair wires.
harness wires #311 or #304 (first
gear) and wires #311 or #305 (sec-
ond gear) have been cut or broken.
5. Second gear solenoid or cartridge 5. Refer to the Problem 7. in this trou-
is bad. bleshooting section.
6. No First Gear 1. Weatherpack from the transmission 1. Ensure weatherpack has good
harness to the control valve for the connection and all pins are seated.
first gear solenoid is loose or dis-
connected.
continued
9C-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

6. No First Gear 2. Shifter to rear panel harness con- 2. Ensure shifter to rear panel har-
(Continued) nector (PC1) is loose or pin 3 of ness connector (PC1) has good
connector is backed out. connection and all pins are seated.
3. Defective solenoid on the first gear 3. Replace first gear solenoid.
cartridge located on the control
valve.
the accessory position. Roll the
shifter to the First gear position.
On the shifter side of the plug,
check for 12 VDC coming out of
the shifter at pin 3. If 12 VDC is
present, the shifter is good.
5. Shifter to rear panel harness wire 5. Isolate and repair wire.
#314 (first gear) has been cut or
broken.
6. Rear panel to main junction 6. Isolate and repair wire.
box harness wire #304 has been
cut or broken.
7. Main junction box to transmission 7. Isolate and repair wire.
harness wires #304 (first gear) or
#311 have been cut or broken.
8. Wire #311 is not grounded properly 8. Reseat the wires at the terminal
at the terminal strip in main junction strip.
box.
7. No Second Gear 1. Weatherpack from the transmission 1. Ensure weatherpack has good
(This failure can- harness to the control valve for the connection and all pins are seated.
not occur by itself. second gear solenoid is loose or
To have no second disconnected.
gear, means first
gear has also 2. Shifter to rear panel harness con- 2. Ensure shifter to rear panel har-
failed. Should nector (PC1) is loose or pin 4 of ness connector (PC1) has good
second gear sole- connector is backed out. connection and all pins are seated.
noid fail, the only 3. Defective solenoid on the second 3. Replace second gear solenoid.
gear available will gear cartridge, located on the con-
be third gear.) trol valve.
continued
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-7

7. No Second Gear 4. Defective shifter. 4. Disconnect the shifter to rear panel

(This failure can- harness plug (PC1). Jumper pin 1
not occur by itself. of plugs together. This jumper
To have no second allows input power (12 VDC) to the
gear, means first shifter. Turn the ignition switch to
gear has also the accessory position. Roll the
failed. Should shifter to the First gear position.
second gear sole- On the shifter side of the plug,
noid fail, the only check for 12 VDC coming out of
gear available will the shifter at pins 3 and 4. If 12
be third gear.) VDC is present, roll the shifter to
(Continued) 2nd gear position. 12 VDC will no
longer be present on pin 3, 12 VDC
will be present on pin 4. If these
checks are good, the shifter is
good.
5. Shifter to rear panel harness wire 5. Isolate and repair wire.
#315 (second gear) has been cut
or broken.
6. Rear panel to main junction box 6. Isolate and repair wire.
harness wire #305 has been cut or
broken.
7. Main junction box to transmission 7. Isolate and repair wire.
harness wires #305 (second gear)
or #311 have been cut or broken.
8. Wire #311 is not grounded properly 8. Reseat the wires to the terminal
at the terminal strip in main junction strip.
box.
9C-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

8. No Third Gear 1. Defective shifter. 1. Disconnect the shifter to rear panel

the accessory position. Roll the
shifter to the Third gear position.
On the shifter side of the plug,
check for 12 VDC coming out of
the shifter at pin 4. If 12 VDC is
present, the shifter is defective or
3rd gear is blocked out (refer to
Cause 4. of Problem 8. of this trou-
bleshooting chart).
2. 12 VDC is present on wire #315 of 2. Isolate and remove 12 VDC from
the panel harness. wire.
3. 12 VDC is present on wire #305 3. Isolate and remove 12 VDC from
of the transmission harness. wire.
4. Third gear has been blocked out. 4. To block out third gear, all that is
required is to keep the Second
gear cartridge solenoid, located on
the control valve, energized all the
times.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-9

Hoist Circuit
9C-10 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 9C-2. Electric Shift ANSI Wiring Circuit
GEAR SELECT SOLENOIDS ENERGIZED

FWD 1ST FWD, 1ST, 2ND
FWD 2ND FWD, 2ND
FWD 3RD FWD
NEUTRAL 1ST 1ST, 2ND
NEUTRAL 2ND 2ND
NEUTRAL 3RD 0
REV 1ST REV, 1ST, 2ND
REV 2ND REV, 2ND
REV 3RD REV
09C-2324 SHT. 02
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 9C-11
Hoist Circuit
9C-12 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Automatic Powershift Control
Introduction. The APC 70 module (an optional HARNESS

device) is a state-of-the-art microprocessor which PIN WIRE# FUNCTION
has been programmed to automatically shift the
transmission. A1 1 BATTERY Power (wire #301)
B1 2 BATTERY GROUND (wire #11)
APC 70 Module (Illustration 9C-3, if equipped). C1 3 Shift Fail Light Return (wire #308)
The APC 70 module continuously monitors the D1 4 Processor Output for Solenoid #1
ground speed, shifter position, and engine speed, (wire #304)
which it uses to shift the transmission automatical- E1 5 Processor Output for Solenoid #2
ly. The APC 70 module is mounted on the dash. (wire #305)
F1 6 Processor Output for Forward
The APC 70 allows directional changes only in 1st
Solenoid (wire #306)
gear and at a vehicle speed of less than 2 mph G1 7 Processor Output for Reverse
(3.2 km/h), and only allows transmission engage- Solenoid (wire #307)
ment in forward or reverse if engine speed is H1 8 Not Used In This Truck
under 1000 rpm. It prevents torque converter and J1 9 Not Used In This Truck
transmission overspeeding by only allowing a K1 10 Signal from Processor to Shift Fail
downshift if the resulting turbine speed does not Light Supply (wire #310)
exceed a pre-set value in 2nd or 3rd gear. A2 11 BATTERY Power (wire #301)
The APC 70 works in conjunction with the roll B2 12 Signal Ground for sensors (wires #348)
shifter (located on the steering column). It will C2 13 Forward Input to processor (wire
automatically upshift and downshift to the highest #352)
D2 14 Reverse Input to processor (wire
gear that is selected at the shifter. If second gear
#354)
is selected at the roll shifter, the APC 70 will shift
E2 15 Shifter Input to processor Solenoid #2
between 1st and 2nd gears. To allow manual
(active in 1st and 2nd gear, wire #315)
shifting, the auto / manual switch must be placed F2 16 RS232 Receive Input
in the manual position. The processor can be G2 17 Not Used In This Truck
bypassed in the event of processor failure with a H2 18 Not Used In This Truck
jumper plug supplied with the truck. To bypass J2 19 Not Used In This Truck
the processor, disconnect the harness from the K2 20 Not Used In This Truck
processor and plug the jumper plug into the con- A3 21 Engine speed hot (inductive pickup,
nector of the harness. wire #321)
B3 22 Used for travel alarm systems / shift
inhibit
Should any truck, equipped with C3 23 Transmission speed (inductive pickup,
an APC 70 module, require welding on its struc- wire #323)
tural members, the metri-pack connector must D3 24 Not Used In This Truck
be unplugged from the APC 70 module prior to E3 25 Shifter Input to processor Solenoid #1
any welding. Failure to comply with this caution (active in 1st gear, wire #314)
may lead to damage to the APC 70 module. F3 26 Used for travel alarm systems
G3 27 RS232 Transmit Output
Display Mode Switch. The display mode switch H3 28 Not Used In This Truck
“M” is located on the front panel (see Illustration J3 29 Manual / automatic mode select (wire
9C-3). When the switch is depressed, the display #309)
will show new information. When the APC 70 has K3 30 Not Used In This Truck
been powered, the normal display (gear position)
is shown. If the switch is depressed, the vehicle Harness Connector Pin and Wire Assignments
speed is displayed in kilometers per hour,
depressing it once again displays the vehicle If the switch is depressed and held during power
speed in miles per hour, and depressing it once up of the APC 70, the self test mode is selected.
more displays the shift lever position. Control of The APC 70 must be powered down and then
the transmission remains no matter what screen is powered up again to reset and resume normal
displayed. shifting operation.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-13

block the wheels in both directions to prevent

Death or serious injury could movement of the truck and Lock Out & Tag Out
result from a runaway truck. Park the truck on the truck.
a hard, level surface, apply the parking brake,
Display Selector Switch Operation
Normal Display Speed Display

Speed Display Input monitoring
showing gear position expressed in
expressed in km/h reflects the inputs
and error messages turbine RPM
RED (F) LED Lit when the APC 70 is in the reset condition
YELLOW (T) Lit to indicate test modes and faults

LED
Illustration 9C-3. APC 70 Module
9C-14 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Diagnostic Codes
APC 70 Normal Display Transmission Status (Display 1)
The normal display indicates the processor output to the transmission.
FWD 1st NEUT 1st REV 1st
processor is processor is processor is
in fwd 1st in net. 1st in rev 1st
gear gear gear
FWD 2nd NEUT 2nd REV 2nd

in fwd 2nd in net. 2nd in rev 2nd
gear gear gear
FWD 3rd NEUT 3rd REV 3rd

in fwd 3rd in net. 3rd in rev 3rd
gear gear gear
Vehicle Speed Display Ground Speed Expressed In km/h (Display 2)

In order to get the vehicle’s speed displayed, the display mode switch must be depressed
once. The display will indicate the vehicle’s speed expressed in kilometers per hour (km/h).
Possible codes:
indicated vehicle speed indicated vehicle speed

is 6.65 - 6.75 km/h is 11.5 - 12.5 km/h
Vehicle Speed Display Ground Speed Expressed In mph (Display 3)

In order to get the vehicle’s speed displayed (expressed in mph), the display mode switch must
be depressed once again. The display will indicate the vehicle’s speed expressed in mile per
hour (mph).
Possible codes:
indicated vehicle speed indicated vehicle speed

is 6.65 - 6.75 mph is 11.5 - 12.5 mph
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-15

Diagnostic Codes (continued)
Shift Lever Position Display (Display 4)
In order to get the shift lever position display, the display mode switch must be depressed once
more. This display indicates control signals from the shifter to the processor.
Possible codes:
FWD 1st NEUT 1st REV 1st
shifter is in shifter is in shifter is in
fwd 1st net. 1st rev 1st
FWD 2nd NEUT 2nd REV 2nd

fwd 2nd net. 2nd rev 2nd
FWD 3rd NEUT 3rd REV 3rd

fwd 3rd net. 3rd rev 3rd
Self Test Mode

Principally, there are no specific devices required for first level troubleshooting as the APC 70
incorporates several self-test features assisting in this process. However, use of digital multi-
meters and simple tools such as an indicator lamp will be required to pinpoint exact causes of
problems. More in-depth troubleshooting and system tuning involves use of an IBM Compat-
ible PC with appropriate software.
To obtain the self test mode, the mode button must be depressed and held down 3 - 5 seconds
during start up of the truck, and then released.
CAUTION: If the mode button is depressed and held more than 10 seconds, the
APC 70 module will default to a programming mode and the APC 70 will then have
to be sent to Taylor Machine Works, Inc. for re-programming.
NOTE: Shutting down the truck leaves the self test mode of the APC 70.
The test modes of the self test mode are the turbine speed monitor, engine speed monitor,
speed ratio monitor, battery voltage monitor, input test, and output test. These test modes are
described below.
9C-16 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Self Test Mode (continued)
Turbine Speed (Must be in Self Test Mode, Display 1)
In order to get the turbine speed displayed, the mode switch must be depressed once. After
releasing the mode button, the display will show the turbine speed RPM (input RPM of the
transmission). If no dot is visible on the display, the value must be multiplied by 10 in order to
get the correct value. If a dot is visible, the value must be multiplied by 100 in order to get the
correct value.
Possible codes:
this segment is flashed when the turbine speed mode has been selected
and followed by the turbine speed
indicated turbine indicated turbine

speed is 630 RPM speed is 1400 RPM
Engine Speed (Must be in Self Test Mode, Display 2)

In order to get the engine speed displayed, the mode switch must be depressed once again.
After releasing the mode button, the display will show the engine speed RPM. If no dot is vis-
ible on the display, the value must be multiplied by 10 in order to get the correct value. If a dot
is visible, the value must be multiplied by 100 in order to get the correct value.
Displayed Mode:
this segment is flashed when the engine speed mode has been selected
and followed by the engine speed
indicated turbine indicated turbine

speed is 750 RPM speed is 2200 RPM
Speed Ratio (Display 3)

In order to get the speed ratio displayed, the mode switch must be depressed once again.
After releasing the mode switch, the speed ratio in the converter will be displayed.
turbine speed
speed ratio = <1
engine speed
Displayed Modes:
this segment is flashed this segment indicates the

when the speed ratio has speed ratio must be less
been selected and is than 1
followed by
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-17

Upshift Speed Ratio (Display 4)
In order to get the upshift speed ratio displayed, the mode switch must be depressed once
again. After releasing the mode switch, the upshift speed ratio mode display will be shown and
then the upshift speed ratio in the converter will be displayed.
Displayed Modes:

when the upshift speed upshift speed ratio
ratio has been selected
and is followed by
Downshift Speed Ratio (Display 5)

In order to get the downshift speed ratio displayed, the mode button must be depressed once
again. After releasing the mode switch, the downshift speed ratio in the converter will be dis-
played.
Displayed Modes:

when the downshift speed downshift speed ratio
ratio has been selected
and is followed by
Battery Voltage (Display 6)

In order to get the battery voltage displayed, the mode switch must be depressed once again.
After releasing the mode switch, the display will show the battery voltage displayed in Volts. If
no dot is visible on the display, the value displayed will have a fractional amount from below
.5 V. If a dot is visible, the value displayed will have a fractional amount above .5 V.
Possible codes:
this segment is illuminated when the battery voltage has been selected
indicated battery voltage indicated battery voltage

is 13.0 - 13.4 V is 13.5 - 13.9 V
9C-18 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Input Test (Display 7)
In order to get the input checking display, the mode switch must be depressed once again.
Instead of showing gear positions and gear direction, the display screen will show the active
inputs. Vehicle operation is possible, the technician can follow the sequence of inputs and thus
verify the wiring of the vehicle. Each segment of the display indicates a specific input.
Different segments can be switched on simultaneously if different inputs are activated simulta-
neously.
Displayed Mode:
this segment is flashed when the input test has been selected
Followed by the possible codes below:

FWD Input
this segment is illuminated when the roll shifter is in the fwd position,
12 VDC will be present on wire 352 and on pin C2 of the harness
connector to the APC 70
REV Input
this segment is illuminated when the roll shifter is in the rev position,
12 VDC will be present on wire 354 and on pin D2 of the harness
connector to the APC 70
TV1 Input
this segment is illuminated when the shifter is in 1st gear, 12 VDC will be
present on wire 314 and on pin E3 of the harness connector to the APC
70
TV2 Input
this segment is illuminated when the shifter is in 2nd gear, 12 VDC will
be present on wire 315 and on pin E2 of the harness connector to the
APC 70
Manual / Automatic Switch

this segment is illuminated when the operator has requested manual
shifting mode, 12 VDC will be present on wire 309 and on pin J3 of the
harness connector to the APC 70
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-19

Output Test (Display 8)
The output test is only valid with the engine not running. If the mode button is depressed while
driving or if a speed sensor fault is detected, the output test will be skipped. The APC 70 gives
information about the status of the outputs. The possible states are: G (good), S (short-circuit
with ground), and O (open load, output is not connected or has a short-circuit to the battery
plus). The APC 70 tests each output sequentially. The left side of the display gives informa-
tion about which output is tested while the right side gives the status of the output. To exit this
final self test mode, the ignition switch must be turned off.
Displayed Mode:
this segment is flashed when the output test has been selected
Possible codes:
Output 1 Output 2 Output 3
wiring and wiring and wiring and
coil for TVF coil for TVR coil for TV1
is good is good is good

wiring or wiring or wiring or
coil for TVF coil for TVR coil for TV1
is shorted is shorted is shorted

wiring or wiring or coil wiring or coil
coil for TVF for TVR is for TV1 is
is open open open
Output 8
Output 4 wiring and
wiring and NOT USED bulb for shift
coil for TV2 fail light is
is good good
Output 4 Output 8
wiring or coil wiring or
NOT USED bulb for shift
for TV2 is
shorted fail light is
shorted
Output 8
Output 4 wiring or
wiring or coil NOT USED bulb for shift
for TV2 is fail light is
open open
9C-20 THDC
THDC/ /THDCP
THDCP- -954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.01/04)
06/03)
Fault Codes
In order to find out which fault was last detected, hold down the mode switch “M” for more than 2 seconds
for the normal display mode. The display will then show, alternately the fault area and the fault type. If
several faults coexist, only the severest one is shown. When this fault display is active, the T-LED will be
blinking to focus the technician’s attention of the current problems.
Listed below are the faults listed in the order of severity (severest fault on top) along with displayed
codes:
Fault Fault Area Fault Type
Direction outputs - one of the outputs has

shorted out to ground

shorted out to a positive voltage

opened
MRS speed sensor failure - open circuit

(TC20000 transmission only)
MRS speed sensor failure - short circuit

(TC20000 transmission only)
Inductive speed sensor failure (transmission or

engine)
Analog (Modulator) output - open connection
Analog (Modulator) output - short circuit
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 9C-21

Fault Fault Area Fault Type
Digital output - short circuit
Digital output - other fault
Incorrect input pattern
Battery voltage - too low
12 VDC input voltage - too high
12 VDC / 24 VDC input voltage missing
Processor Failure
(Internal problem - replace)
9C-22 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 9C-4. Electric Shift With APC 70 ANSI Wiring Circuit
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 9C-23
9C-24 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
100 Ohm, 1.5 Kw RESISTOR
REQUIRED FOR V28 AND BELOW
MODEL APC PROCESSORS
09F-0084 SHT. 02
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 9C-25
Hoist Circuit
9C-26 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Section 11
Drive Shaft
TRANSMISSION
TO AXLE
DRIVE SHAFT
SPLINES
CROSS
ASSEMBLY
CENTERLINES MUST
BE PARALLEL
Illustration 11-1. Transmission to Axle Drive Shaft

Introduction. The drive shaft connects the trans-
mission to the drive axle. It is important to always
have the transmission in phase with the drive axle
(See the note below).
Lubrication (Illustration 11-1). The drive shaft,
universal joints and slip joints should be greased
monthly or every 250 hours, whichever comes
first.
NOTE: When the transmission to axle drive shaft
is installed, the cross assemblies, on the drive
shaft, must be aligned as shown in Illustration
11-1. If the flanges are not aligned, reposition the
splines to bring the flanges into alignment.
If this is not followed, the drive shaft will be out of

phase, and vibration and noise may occur.
Drive Shaft Bolts Inspection (Illustration 11-1).
The bolts, which connect the drive shaft to the
brake disc and drive axle, should be checked for
tightness every 6 months or 1500 hours, whichev-
er comes first. If tightening is required, apply a
torque value of 110 ft-lbs to the bolts.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 11-1

1-12 RTGP-9042N (9/01)
Section 13
Steer Axle
Introduction. The steer axle is mounted to the Mounting Bolts Check (Illustration 13-1). The
frame with two pivot pins. The pivot pins are an mounting bolts of the steer axle should be
integral part of the axle. Pivot pin bushings are checked for tightness every 6 months or 1500
installed on the front and rear pivot pins. All rou- hours of operation, whichever comes first. If the
tine maintenance can be accomplished with the mounting bolts require torquing, remove the
steer axle connected to the frame. mounting bolts, clean bolts, apply LoctiteR to the
threads of the bolts and torque bolts to 405-450
Lubrication. Refer to the Lubrication section in
ft-lbs.
the Appendices for information on lubricating the
steer axle. Steer Cylinder Mounting Bolts (Illustration 13-1).
The cylinder mounting bolts should be checked for
tightness every 6 months or 1500 hours of opera-

Before checking or servicing tion, whichever comes first. If there is any evi-
the steer axle, park on level ground, apply the dence of threading or movement of the steer cylin-
parking brake, block the wheels, shut down der, then remove the mounting bolts, clean bolts,
the engine, and Lock Out & Tag Out the truck. apply LoctiteR to the threads of the bolts and
torque bolts to 405-450 ft-lbs.
STEER AXLE
MOUNTING BOLT
STEER CYLINDER
MOUNTING BOLT
Illustration 13-1. Steer Axle
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 13-1

1-12 RTGP-9042N (9/01)
Section 14
Drive Axle
1. AXLE HOUSING OIL BLEEDER VALVE

LEVEL CHECK / FILL
PLUG
2. HUB CHECK PLUG BRAKE COOLING
3. HUB DRAIN PLUG INPUT PORT
4. DRIVE AXLE 6
5. AXLE HOUSING DRAIN
PLUG
6. BREATHER 1
7. FORCED COOLING
DRAIN PLUG
HIGH PRESSURE
BRAKE APPLY PORT
BRAKE
COOLING
4 OUTPUT
PORT
5
7
POSITION PLUG HERE TO FILL

OR CHECK LEVEL
POSITION PLUG
HERE TO DRAIN
Illustration 14-1. Drive Axle with Wet Disc Brakes

Introduction. The drive axle is equipped with gear reduction at the wheels. Positive full flow
double reduction gearing. The first gear reduction lubrication assures adequate lubrication to all
is a hypoid type ring gear and pinion. The second moving parts under all operating conditions.
reduction is in the form of planetary gears inside
Checking Lube Oil Level (Illustration 14-1). The
the hubs. This arrangement permits the axle
oil in the differential and the planetary hubs should
shafts and hypoid gearing to carry only a nominal
be checked monthly or every 250 hours, whichev-
torsional load while providing the highest practical
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 14-1

er comes first. Perform the following procedures serviced.
to check the oil level and service the differential S Before checking or servicing the drive axle,
and planetary hubs. apply the parking brake, block the wheels,
shut down engine and Lock Out & Tag Out
the truck.

S The machine should be parked on a level
surface when the drive axle is being Dispose of used oil in accor-
serviced. dance with federal and local regulations.
S Before checking or servicing the drive axle,
apply the parking brake, block the wheels, 1. Differential
shut down engine and Lock Out & Tag Out a. Provide a suitable container to catch
the truck. draining oil, then remove axle housing
1. Differential drain plug (5) and axle housing oil level
check / fill plug (1).
a. Check the oil level in the differential by
removing the axle housing oil level check / b. Once oil has completely drained, install
fill plug (1). axle housing drain plug (5) and service
differential with recommended lubricant up
b. The oil level should be even with the bot- to the bottom of axle housing oil level
tom of the oil level check plug hole. Fill the check / fill plug (1) hole.
differential to this level if the oil level is too
low. c. Reinstall axle housing oil level check / fill
plug (1).
c. Reinstall the axle housing oil level check /
fill plug (1). 2. Planetary Hubs
2. Planetary Hubs a. Position the machine so that the hub drain
plug (3) for one of the planetary hubs is at
a. Maneuver the machine until the hub check the bottom of its hub.
plug (2) on one of the planetary hubs is
horizontal with the center of the hub. b. Provide a suitable container to catch oil,
then remove the hub drain plug (3).
b. Remove the hub check plug (2). The oil
level should be even with the bottom of the c. Once the oil has completely drained, rein-
oil check plug hole. Fill the planetary hub stall the hub drain plug (3). Position the
to this level if the oil level is too low. machine so that the hub check plug (2) is
in the 9 o’clock position of the hub rotation.
c. Reinstall the hub check plug (2). Fill the hub with the specified gear oil until
d. Reposition the machine as necessary and oil level is at the bottom of the hub check
service the hub on the opposite end of the plug (2). Reinstall the hub check plug.
axle by repeating the above procedures. d. Follow the above procedures for servicing
NOTE: When the drive axle is completely serv- the hub on the other side of the drive axle.
iced, the oil is at a common level in the differential General Information
and both hubs.
Oil Capacities
Changing The Oil (Illustration 14-1). The oil in Differential & Axle Housing 80 Quarts
the differential and planetary hubs should be Planetary Hub (each) 13 Quarts
changed yearly or every 3000 hours, whichever
comes first. Refer to the Fuel and Lubricant
Specifications in the Appendices for the type of Draining The Wet Disc Brakes Hydraulic Fluid
oil to be used in the drive axle. Perform the fol- From The Brake Housings (Illustration 14-1).
lowing procedures to change oil in the drive axle. The hydraulic fluid is part of the hydraulic system
and will be changed when the hydraulic tank’s
fluid is changed. Change the hydraulic fluid yearly

or 3000 hours, whichever comes first. Refer to
S The machine should be parked on a level Changing The Hydraulic Fluid in Section 22 to
surface when the drive axle is being change the hydraulic tank fluid and perform the
14-2 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
following procedures to change the hydraulic fluid NOTE: Should more detailed service of the drive
from the brake housing. axle components be required, refer to Rockwell
Wet Disc Brakes Maintenance Manual No. 4L.
Dispose of used hydraulic

fluid in accordance with federal and local regu-
lations.
1. Remove either the brake cooling input port or
brake cooling output port hydraulic hose
assembly from the brake housing.
2. Provide a suitable container to catch drained
hydraulic fluid and remove the forced cooling
drain plug (7) from brake housing to drain
cooling fluid.
3. After cleaning the forced cooling drain plug
(7), reinstall and apply a torque value of 18 -
25 ft-lbs. to tighten the drain plug.
4. Connect the hydraulic hose assembly
removed in procedure 1. to the brake housing.
5. Perform procedures 1. through 4. to remove
the hydraulic fluid from the brake housing on
the opposite end of the drive axle.
6. After filling the hydraulic tank with the specified
amount of fluid (refer to Changing The
Hydraulic Fluid in Section 22), place the
transmission in the neutral position and start
the engine to restore the movement of hydrau-
lic fluid.
Cleaning The Breather (Illustration 14-1). The
differential breather should be cleaned whenever
the drive axle hydraulic fluid is changed. Perform
the following procedures to clean the breather.
1. Wipe away any dirt or grime on the breather
(6) and surrounding area before removing the
breather.
2. Remove the breather (6).
3. Wash the breather by agitating it in solvent
and dry with compressed air.
4. Inspect the breather. If it is damaged or
clogged, install a new breather.
Inspection. The drive axle mounting bolts should
be inspected every 6 months or 1500 hours,
whichever comes first. If there is any evidence of
threading or movement of the drive axle, then
loosen locknuts, clean threads, apply LoctiteR to
threads and torque the locknuts on the mounting
bolts to 1350-1500 ft-lbs.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 14-3

Drive Axle Troubleshooting
1. Brakes Do Not 1. Empty fluid reservoir. 1. Fill reservoir to correct level with
Apply (low or no specified fluid.
pressure to
brakes) 2. Damaged brake control (air) sys- 2. Repair the brake control (air) sys-
tem. tem.
3. Leakage of brake actuation fluid. 3. Refer to Problems 7. and 8. in this
troubleshooting chart.
2. Brakes Do Not 1. Debris in the brake housing. High 1. Loosen the bleeder valve (10,
Release (truck pressure brake apply fluid enters Illustration 14-1) to bleed off high
does not move) into the brake housing, behind the pressure brake apply fluid.
piston through a small passage. Remove the high pressure brake
When the brakes are released, the apply hose from the brake housing.
high pressure fluid used to apply Insert a small piece of wire into the
the brakes must exit through the passage and dislodge the debris.
same small passage. Re-connect the high pressure
brake apply hose to brake housing
and perform the Wet Disc Brake
Bleeding procedures in Section
15.
3. Brakes Do Not 1. More than 20 psi (1.4 bar) pressure 1. Refer to Correction 1. of Problem
Release (brakes applied when brakes released. 2. in this troubleshooting chart.
dragging)
2. Damaged piston return spring 2. Repair or replace piston return
assembly. spring assembly.
3. Piston not returning. 3.
a. Check piston seals and seal
separator for swelling or dam-
age. Replace as necessary.
b. Refer to Correction 1. of Prob-
lem 2. in this troubleshooting
chart.
4. Wrong cooling and / or actuation 4. Check piston seals and seal sepa-
fluid used. rator for swelling or damage.
Replace as necessary. Purge sys-
tem and use specified fluid.
5. Tight or damaged splines (eg., fric- 5. Repair or replace parts.
tion disc-to-hub driver).
14-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

4. Braking Perfor- 1. Inadequate actuation fluid supply 1. Replenish fluid in brake system.
mance (noticeable to brakes. Check for leakage and correct
change or cause.
decrease in stop-
ping performance) 2. Inadequate pressure to apply 2. Refer to Problem 3. of the Brake
brakes. Control (Air) System Trouble-
shooting chart in Section 15.
3. Worn or damaged discs. 3. Inspect and replace discs if neces-
sary. Note: As disc wear occurs,
make sure brake system can sup-
ply adequate fluid to fully apply
brakes.
4. Overheated seals and / or discs. 4. Inspect and replace discs and
seals if necessary.
5. Dirty or contaminated cooling fluid. 5. Drain and flush cooling fluid from
brakes and entire brake system.
Replace with approved fluid. In
some cases, it may be necessary
to replace discs. Clean or replace
filter.
5. Braking Perfor- 1. Empty or low brake reservoir. 1. Fill brake reservoir to correct level
mance (brakes do (3/4” from the top of the reservoir)
not fully apply) with specified fluid.
2. Damaged brake control (air) sys- 2. Repair the brake control (air) sys-
tem. tem.
3. Leakage of brake actuation fluid. 3. Refer to Problems 7. and 8. in this
6. Braking Perfor- 1. Brakes or brake system not proper- 1. Bleed brakes and brake system.
mance (brakes ly bled.
feel spongy / soft)
7. Brakes Leak 1. Worn or damaged piston seal. 1. Replace piston seals.

Actuation Fluid
2. Melted or extruded piston seals. 2. Correct cause of overheating and
(Internal leak: fluid
replace seals.
bypasses the pis-
ton seals into 3. Corrosion, pitting, wear or other 3. Clean, smooth, rework or replace
brake cavity and damage, marks, scratches to pis- affected parts.
mixes with brake ton and / or brake housing bore in
cooling fluid). area of seal / sealing lips.
4. Damaged power cluster seals. 4. Repair power cluster.
5. Wrong type of actuation fluid. 5. Refer to the Fuel and Lubricant
Specifications in the Appendices
for the correct type of fluid to use.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 14-5

8. Brakes Leak 1. Loose bleeder screw. 1. Tighten bleeder screw to 15-20 ft-
Actuation Fluid lbs (20-27 N⋅m).
(external leak)
2. Loose inlet fitting or plugs. 2. Tighten inlet fitting to 25-35 ft-lbs
(34-47 N⋅m).
3. Damaged inlet fitting or plugs or 3. Replace inlet fitting or plug and O-
damaged seats. ring if used. Repair or resurface
area; or replace as necessary.
9. Brake Cooling 1. Face seal damaged, worn or 1. Reinstall and / or replace face seal.
Fluid Leakage improperly installed.
(coolant leaking
2. Loose drain plug, fill plug or forced 2. Tighten plug.
out of brake hous-
ing) cooling plug.
3. Damaged plug. 3. Replace plug.
4. Deteriorated or inadequate sealant 4. Disassemble, clean, re-seal and
used at joint. reassemble joint.
10. Brake Cooling 1. Worn or damaged spindle to hub 1. Replace spindle to hub seal and
Fluid Leakage seal. check seal. Journals.
(axle housing fill-
ing with fluid and
may be forced out
the breather)
11. Brake Noise and 1. Incorrect cooling fluid and / or fric- 1.

Vibration (brakes tion material used.
a. Use only specified or approved
produce noise,
materials.
chatter, vibration).
b. Drain and flush cooling fluid
from brake system. Replace
with approved fluid.
c. Replace all friction discs. Thor-
oughly clean or replace station-
ary discs.
12. Brake Overheats 1. Low pump output, blocked filter or 1. Check pump output at different
(inadequate cool- coolant lines. operating modes. Replace filter
ing fluid flow) and check lines.
2. Dirty or clogged brake cooler. 2. Externally clean brake cooler.
13. Loss of Oil Out of 1. Damaged or badly worn pinion 1. Replace oil seal and check for
Differential shaft oil seal. loose pinion bearings or pinion nut.
continued
14-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

13. Loss of Oil Out of 2. Loose carrier mounting bolts. 2. Check and tighten mounting bolts.
Differential Replace gasket if damaged or bro-
(Continued) ken.
3. Breather in differential housing 3. Clean breather; replace if dam-
plugged, forcing oil by seals. aged.
14. Noisy Differential 1. Low oil level. 1. Fill to correct level with recom-
(Constant Noise) mended lubricant (see lubricant
specifications).
2. Incorrect lubricant. 2. Drain, flush and refill with lubricant
of recommended specifications.
3. Incorrect bearing adjustment. 3. Adjust bearings. Replace any that
are damaged or excessively worn.
4. Breather in differential housing 4. Clean breather; replace if dam-
plugged. aged.
5. Oil level too high. 5. Drain oil down to check plug level
in differential.
6. Defective hub seal. 6. Replace hub seal.
7. Worn bearings. 7. Replace bearings.
8. Chipped gear teeth. 8. Replace gear.
15. Noisy Differential 1. Ring gear and pinion adjustment is 1. Adjust ring gear and pinion.
(Noise on Drive) too loose (excessive backlash).
a. Drive shaft is out-of-phase a. When the transmission to axle
drive shaft is installed, the flanges
on the drive shaft, must be aligned
as shown in Illustration 11-1. If the
flanges are not aligned, reposition
the splines to bring the flanges into
alignment. If this is not followed,
the drive shaft will be out of phase,
and vibration and noise may occur.
16. Noisy Differential 1. Ring gear and pinion adjustment is 1. Adjust ring gear and pinion.
(On Coast) too tight (insufficient backlash).
17. Noisy Differential 1. Worn or damaged differential pin- 1. Replace differential parts.
(Noise on Turns) ion gears, side gears or pinion jour-
nals.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 14-7

18. Noisy Final Drives 1. Low oil level. 1. Fill to correct level with specified
(Planetary Axles) lubricant.
2. Incorrect type and grade lubricant. 2. Drain, flush, inspect, repair if nec-
essary; install specified lubricant.
3. Wheel bearings improperly 3. Adjust wheel bearings to recom-
adjusted. mended preload.
4. Worn bearings in wheels or planet 4. Replace bearings.
gears.
5. Chipped gear teeth. 5. Replace gears.
6. Scored planet pins. 6. Inspect and replace defective
parts.
19. Loss of Oil Out of 1. Damaged or broken wheel driver 1. Replace gasket.
Final Drives gasket.
(Planetary Axles)
2. Damaged or broken hub cap gas- 2. Replace gasket.
ket.
3. Damaged or excessively worn 3. Replace oil seals and adjust wheel
wheel oil seals. bearings properly.
4. Loose wheel bearings. 4. Adjust wheel bearings properly and
replace oil seal.
20. Brake Oil Level is 1. Brake piston seals possibly leak- 1. Replace seals if necessary.
Continuously Low ing.
With No Signs of
External Leakage
21. Gear Oil Level in 1. Seal between brake housing and 1. Replace seal if necessary.
Hub is Continu- wheel hub may be leaking.
ously Too High
2. Cooling oil pressure too high. 2. Have brake coolant pressure relief
valve cartridge replaced.
22. Signs of External 1. Clean surface and then determine 1. Replace seals.
Leakage Exist location of leakage.
14-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Section 15
Brake Control (Air) System

Introduction. The brake control system controls the illustrations as indicated for identification of
the slowing down and stopping of the truck. Air parts.
pressure from the air tanks is controlled by the
Air Governor (Illustration 15-1). The air governor
foot operated brake valves (pedals), directly actu-
operates in conjunction with the air compressor
ating the brake relay valve. System air pressure,
unloading mechanism and controls system air
stored at the brake relay valve, is then routed to
pressure between a predetermined maximum and
the power cluster, applying the service brakes. If
minimum pressure. The air pressure reading of
the left brake valve is depressed, in addition to
the system should be a normal operating pressure
applying the brakes, the air pressure is routed to
of 105 psi. The air governor should be checked
the transmission control valve which de-clutches
for proper adjustment. Perform the following pro-
and neutralizes the transmission.
cedures to adjust the air governor. Refer to
Major Components (Illustration 15-2). The brake Illustration 15-1 for identification of governor parts.
control system consists of an engine driven air
1. Shutdown the engine and deplete air pressure
compressor, air governor, air tanks (one with a
by pulling the drain valve pull cable.
manual drain valve), de-clutch control / service
brake valve pedal (LH), service brake valve pedal
(RH), brake relay valve, shuttle valve, parking
When adjusting the air pres-
brake valve, parking brake actuator, power cluster, sure on the air governor, the engine must be
brake reservoir and an air horn circuit. Refer to shut down to avoid bodily injury.
INSTRUMENT PANEL
AIR PRESSURE GAUGE
1. COVER
2. AIR GOVERNOR
3. NUT
4. SETSCREW
2
4
1
CROSS SECTION OF AIR GOVERNOR
Illustration 15-1. Air Governor
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15-1

SERVICE
BRAKE VALVE
(Illustration 15-4)
DE-CLUTCH
AIR PRESSURE GAUGE
CONTROL / SERVICE
(Illustration 15-1)
BRAKE VALVE
(Illustration 15-4)
PARKING BRAKE VALVE
AIR GOVERNOR (Illustration 15-6)
(Illustration 15-1)
AIR TANKS
(Illustration 15-3)
SHUTTLE VALVE &

BRAKE RELAY VALVE
(Illustration 15-5)
BRAKE RESERVOIR
(Illustration 15-8)
AIR TANKS DRAIN

VALVE PULL CABLE
(Illustration 15-3)
BRAKE COOLING
OIL FILTER
(Illustration 15C-3)
BRAKE
MANIFOLD VALVE
POWER CLUSTER (Illustration 15C-1)
(Illustration 15-8)
PARKING BRAKE
BRAKE COOLING VALVE (Illustration 15-7)
(Illustration 15C-2)
Illustration 15-2. Brake Control System Components Identification
15-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

INDICATES SYSTEM AIR FLOW
INDICATES AIR SIGNAL TO
TURN OFF GOVERNOR
CHECK
VALVE
AIR TANK
DRAIN VALVE
SAFETY
VALVE
AIR TANK
DRAIN VALVE
PULL CABLE DRAIN
VALVE DRAIN VALVE
PULL CABLE
Illustration 15-3. Air Tanks Components

2. Unscrew the cover (1) from the air governor 6. After obtaining the correct air pressure, tighten
(2). the nut (3) and reinstall cover (1).
3. Loosen the nut (3) and turn the set screw (4) Air Tanks (Illustration 15-3). All compressors
counterclockwise to increase air pressure or pass a certain amount of oil in order to lubricate
clockwise to decrease air pressure. the cylinder walls and piston rings. Also, depend-
ing on the humidity, air entering the compressor
4. Then start the engine and check the air pres-
contains a certain amount of water. This oil and
sure by looking at the air pressure gauge on
water normally enters the air tanks in the form of
the dash instrument panel.
vapor because of the heat generated during com-
5. If air pressure is above or below the normal pression. After reaching the air tanks, they con-
operating pressure, repeat procedures 1. dense to form water emulsion that must be
through 4. to obtain the proper operating air drained off before entering the brake system. The
pressure. air tanks are used to store air in order to build
pressure for brake actuation.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15-3

Manual Drain Valve (Illustration 15-3). One of er comes first, for cracks and tight connections to
the air tanks is equipped with a manually operated the fittings on the components.
drain valve to drain any collection of oil and water
Brake Valves (Illustration 15-4). There are two
emulsion from the air tanks. The air tank
brake valves used to stop the truck. The service
equipped with the manual drain valve should be
brake valve (RH - right-hand) actuates the wheel-
drained daily by pulling the cable (located on the
end brakes when the brake pedal is applied. The
right side behind the front tires) out and holding it
de-clutch / service brake valve (LH - left-hand) dis-
open until all moisture has evacuated.
engages the transmission and applies the wheel-
end brakes when the brake pedal is applied.
The safety valve (Illustration Shuttle Valve (Illustration 15-5). The shuttle
15-3) has been preset at factory to release air valve is used to isolate the air flow from the two
pressure at 135 psi. Do not attempt to change brake valves.
the adjustment.
Brake Relay Valve (Illustration 15-5). The brake
Air Hoses. All air hoses should be checked relay valve is used to reduce the time required to
monthly or every 250 hours of operation, whichev- build maximum brake apply air pressure. The
brake relay valve is supplied with a constant 105
RH
D
S
SERVICE
BRAKE VALVE
LH
D
S
DE-CLUTCH /
SERVICE
BRAKE VALVE
SYSTEM AIR
D - DELIVERY
S - SOURCE LOW AIR
INDICATES AIR FLOW SWITCH
Illustration 15-4. Brake Valves
15-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

SHUTTLE ues to drop and falls below 60 psi, the parking
VALVE brake valve will automatically pop out and apply
the parking brake.
Air pressure in the brake system must be above
60 psi and the parking brake valve must be
pushed in to release the parking brake after it has
been applied. If the parking brake valve is pushed
in when the air pressure in the brake system is
below 60 psi, it will immediately return to the out
position and the brake will not release.
Parking Brake Linings (Illustration 15-7). The
parking brake linings should be checked for wear
every 6 months or 1500 hours, whichever comes
first (under extreme duty cycles, this check may
be required more frequently). The parking brake
linings should be replaced before the brake lining
BRAKE
friction material reaches a thickness of 0.200” (5.1
RELAY
mm). The parking brake linings must be replaced
VALVE
in pairs.
Parking Brake Linings Removal (Illustration
15-7). Perform the following procedures to
remove the parking brake linings:
1. Block the wheels of the truck, apply the park-
ing brake, shut down the engine and Lock Out
& Tag Out the truck.
2. Drain the air tanks by pulling the drain valve
INDICATES AIR FLOW
pull cable (located on the right side behind the
front tires) out and holding it open until all air
Illustration 15-5. Brake Relay Valve pressure has been exhausted.
3. Remove the front two decking panels from the
psi air pressure (system air pressure). When truck to gain access to the parking brake
either brake valve pedal is applied, an air signal is assembly.
sent to the brake relay valve, diverting the system
air pressure to the power cluster to activate the 4. Remove the release tool (1, located on the
drive axle brakes. side pocket of the air chamber).
Parking Brake Valve (Illustration 15-6). The 5. Remove the dust plug (4) from the key hole,
parking brake valve is located under the instru- located on the back of the air chamber.
ment panel and when pushed in, supplies air 6. Insert release tool’s stud (1) through the key
pressure to release the spring applied parking hole of the air chamber into the pressure plate.
brake, disengaging the parking brake caliper Note that the release tool’s stud is illustrated
located on the drive axle. When the parking brake (in Illustration 15-7), inserted into the key hole
valve is pulled out, the air pressure is released of the air chamber.
and an internal spring in the parking brake cham-
ber engages the caliper to apply the parking 7. Turn the release tool (1) 1/4 turn clockwise.
brake. 8. Pull on the release tool (1) to ensure stud
If for any reason the air pressure in the system crosspen is properly seated in the pressure
drops below 75 psi, the LOW AIR warning light, plate.
located on the dash, will illuminate and a buzzer 9. Assemble the release stud washer (3) and
will sound to warn of low air pressure in the brake nut (2) on the release tool’s stud (1) finger
system. If the air pressure in the system contin- tight.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15-5

KNOB
PARKING BRAKE
VALVE (PP1)
TO PARKING BRAKE
AIR CHAMBER
PARKING
BRAKE
SWITCH
SUPPLY FROM
INDICATES AIR FLOW LH SERVICE
BRAKE VALVE
Illustration 15-6. Parking Brake Valve
10. To retract the compression spring of the air S Do Not use an impact wrench to tighten the
chamber, tighten the release stud nut (2) with release stud nut (2).
a hand wrench. Make sure the push rod (17)
is retracting. 11. Continue to tighten the release stud nut (2)
until the release tool’s threads are a minimum
of 3.25” beyond the release stud nut.

S If the air chamber shows structural damage,
Do Not attempt to perform procedure 10.

Replace air chamber immediately. Do Not S Overtorquing of the release stud nut (2) can
attempt to repair air chamber, only replace- cause pressure plate damage.
ment is authorized. S If this minimum measurement (3.25”) cannot
S The air chamber contains a very powerful be attained by use of the hand wrench only,
compression spring. Do Not attempt to the air chamber is structurally damaged.
disassemble the air chamber. The spring in Discard and replace the air chamber.
the air chamber can release with enough 12. Locate the adjuster plug (5) on the air cham-
force to cause death or severe personal ber mounting bracket (6). Remove the adjust-
injury. er plug and washer from the air chamber
S Do not stand directly in front of the air cham- mounting bracket allowing access to the
ber when tightening the release stud nut (2). adjuster screw.
Stand to the side of the air chamber.
15-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

16 15
11 1. RELEASE TOOL
2. RELEASE STUD NUT
3. RELEASE STUD WASHER
12 4. DUST PLUG
5. ADJUSTER PLUG
6. AIR CHAMBER MOUNTING
BRACKET
14 7. RETAINER PIN
8. STABILIZER BAR PIN
10 9. STABILIZER BAR
10. BRAKE LINING
11. SPRING
12. SHIM
7 13. CALIPER
8 14. BRAKE LINING
9
15. SPRING
16. SHIM
18 13 17. PUSH ROD
18. LOAD PLATE
17 1
4
6
Illustration 15-7. Parking Brake Adjustment and Brake Lining Replacement

13. Use a 6 mm hex wrench to de-adjust the park- stop turning the hex wrench when you feel
ing brake. Turn the adjuster screw counter- resistance, which indicates that the adjuster
clockwise to increase disc clearance. During pistons are fully retracted. If you continue to
brake de-adjustment, stop turning the hex turn the hex wrench beyond the resistance
wrench when you feel resistance, which indi- point, the adjuster pistons may lock in the
cates that the adjuster pistons are fully sleeves and damage the internal components.
retracted.
14. Remove the retainer pin (7) and stabilizer bar
pin (8), and swing the stabilizer bar (9)
Use a hex wrench to manually towards the air chamber so that it is out of the
adjust and de-adjust the parking brake. Do not way.
use an air gun. During brake de-adjustment,
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15-7

15. Lift the brake lining (10) and spring (11) 8. Install the washer and adjuster plug (5). Tight-
assembly, closest to the air chamber, out of en the adjuster plug to a torque of 8 - 12 ft-lbs
the caliper assembly. (11 - 17 N⋅m).
16. Slide the caliper (13) towards the drive axle 9. Swing the stabilizer bar (9) into its original
and remove the brake lining (14) and spring position and install the stabilizer bar pin (8)
(15) assembly closest to the drive axle. and retainer pin (7).
NOTE: If the caliper (13) moves past its working 10. Reinstall the two decking panels on the truck.
position and jams on the slide pins, use a rubber Parking Brake Linings Adjustment (Illustration
mallet to move the caliper back to its working 15-7). The parking brake linings adjustment pro-
range. cedures must be performed when the parking
brake linings have been replaced. Perform the
17. Verify that the caliper (13) slides freely on the following procedures to adjust the parking brake
slide pins. linings:
18. Remove dirt and dust from the brake lining 1. Block the wheels of the truck, apply the park-
contact surfaces of the the saddle. ing brake, shut down the engine and Lock Out
19. Inspect the caliper boots. If the boots are & Tag Out the truck.
damaged, replace the caliper. 2. Drain the air tanks by pulling the drain valve
Parking Brake Linings Installation (Illustration pull cable (located on the right side behind the
15-7). Perform the following procedures to install front tires) out and holding it open until all air
the parking brake linings: pressure has been exhausted.
1. Install the brake lining (14) and spring (15) 3. Remove the front two decking panels from the
assembly in the drive axle side of the caliper. truck to gain access to the parking brake
assembly.
2. Slide the caliper (13) towards the air chamber
and install the brake lining (10) and spring (11) 4. On the air chamber mounting bracket (6),
assembly in the air chamber side of the cali- locate the adjuster plug (5). Remove the
per. adjuster plug and washer from the air chamber
mounting bracket allowing access to the
3. Remove the release stud nut (2) and release adjuster screw.
stud washer (3) from the release tool (1).
5. Adjust the initial caliper clearance:
4. Turn the release tool (1) 1/4 turn counterclock-
wise to remove the tool from the air chamber. a. Using a 6 mm hex wrench, reduce the cali-
per-to-disc clearance to zero by turning the
5. Insert the release tool in the side pocket of the wrench clockwise.
air chamber and secure with release stud
washer (3) and stud nut (2). b. Check that the load plate (18) is in full con-
tact with the lining backing plate.
6. Reinstall the dust plug (4) into air chamber key
hole. c. Turn the adjuster screw (5) counterclock-
wise 7 clicks (approximately 2/3 of a turn)
7. Adjust the initial caliper clearance: to increase the disc clearance.
a. Using a 6 mm hex wrench, reduce the cali- 6. Install the washer and adjuster plug (5). Tight-
per-to-disc clearance to zero by turning the en the adjuster plug to a torque of 8 - 12 ft-lbs
wrench clockwise. (11 - 17 N⋅m).
b. Check that the load plate (18) is in full con- 7. Reinstall the two decking panels on the truck.
tact with the brake lining backing plate.
Power Cluster (Illustration 15-8). The power
c. Turn the adjuster screw counterclockwise cluster, mounted on the right side of the chassis,
7 clicks (approximately 2/3 of a turn) to converts the air pressure to high hydraulic fluid
increase the disc clearance. pressure to apply the service brakes. The power
cluster for the PRC-7534 drive axle operates on a
14.8 to 1 ratio (example, 105 psi of air pressure
15-8 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
BRAKE RESERVOIR
AIR FROM
BOTTOM OF
RELAY VALVE
FLOW PATH
INDICATES AIR FLOW
INDICATES HYDRAULIC
FLUID FLOW
BLEEDER
VALVE POWER
CLUSTER
QUICK
PRESSURE
CHECK
TO
BRAKE BREATHER
HOUSING
Illustration 15-8. Power Cluster and Brake Reservoir Components

will yield approximately 1554 psi of hydraulic lic Fluid when adding hydraulic fluid to the brake
brake apply pressure). Should the power cluster reservoir.
overstroke, the overstroke switch (S27, Illustration
6-12) will close, sending ground to the Brake Fail
light (DS8), illuminating the Brake Fail light. Do not use DOT 3 brake fluid
in the brake reservoir. Use only the specified
The power cluster has a breather, located on the fluid found in the Fuel and Lubricant Specifica-
power cluster itself, that vents the air from the tions in the Appendices.
power cluster. Replace the breather if it becomes
clogged. Checking The Brake Reservoir Hydraulic Fluid
Brake Reservoir (Illustration 15-8). The brake (Illustration 15-8). The hydraulic fluid used for
reservoir, located on the chassis in front of the fuel brake apply is stored in the brake reservoir and
tank and can be accessed from a brake reservoir should be checked monthly or every 250 hours,
access door, contains the hydraulic fluid utilized whichever comes first, to maintain the proper fluid
by the power cluster to apply the service brakes. level. The capacity of the brake reservoir is
Refer to Checking The Brake Reservoir Hydrau- approximately 1 pint. The brake reservoir should
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 15-9
be filled 1/2” from the top of the reservoir. The tinuing to check the level of fluid in the brake
hydraulic fluid used in the brake reservoir is the reservoir. Do Not let the remote reservoir fluid
same type hydraulic fluid used in the hydraulic level get low.
tank. When adding hydraulic fluid to the brake
9. Bleed the right and left service brakes by fol-
reservoir, care must be taken to remove the rub-
lowing the procedures listed below.
ber boot from the reservoir. Use only specified
brake reservoir hydraulic fluid (refer to the Fuel Right and Left Service Brakes (Illustration 14-1).
and Lubricant Specifications in the Appen- The right and left service brakes must be bled
dices). after performing the Power Cluster bleeding pro-
cedures listed above. Perform the following pro-
cedures to bleed the service brakes.

S The rubber boot of the brake reservoir can
be sucked down as the fluid is drawn into
Before checking or servicing
the power cluster. Do not add fluid before the drive axle, park truck on level ground,
removing the rubber boot from the brake apply the parking brake and block the wheels.
reservoir housing.
1. With the engine running and at normal operat-
S Do not use DOT 3 brake fluid in the brake ing air pressure, have someone apply one of
reservoir. Use only the specified fluid found the service brake pedals and hold it down.
in the Fuel and Lubricant Specifications in
the Appendices. 2. Open the bleeder valve (15) about 1/2 turn on
the left front wheel brake housing allowing air
Changing The Brake Reservoir Hydraulic Fluid and oil to vent.
(Illustration 15-8). The fluid should be changed
only when the brake reservoir is removed or 3. Close the bleeder valve (15).
replaced. 4. Then release the brake pedal.
Wet Disc Brake Bleeding. Bleeding the wet disc 5. Repeat procedures 1., 2., 3. and 4. until a
brake system requires two servicemen; one to bubble-free flow of fluid is observed while con-
operate the service brake pedal and another to tinuing to check the level of fluid in the brake
open and close the bleeder valves. reservoir. Do Not let the remote reservoir fluid
Power Cluster (Illustration 15-8). The power clus- level get low.
ter Must be bled before bleeding the wheel brake 6. Repeat procedures 1. through 5. to bleed the
housings. Perform the following procedures to right service brake.
bleed the power cluster.
De-clutch Operation. When the left brake pedal
1. Park the truck on level ground and apply the is depressed, the transmission will be neutralized.
parking brake. With de-clutch, the transmission is fully engaged
2. Make sure brake reservoir is full (see Check- or disengaged. The right brake pedal will not
ing The Brake Reservoir Hydraulic Fluid). neutralize the transmission when the right brake
pedal is applied.
3. Start the engine and allow the air pressure to
build to normal operating pressure. Coalescing Filter (Illustration 15-9). The coalesc-
ing filter removes water and oil out of the air sup-
4. Have someone apply one of the service brake ply of the horn circuit. This air supply passes
pedals and hold it down. through an electrically-operated solenoid valve
5. Open the bleeder valve on the power cluster which activates the air horn. The coalescing fil-
about 1/2 turn, allowing air and oil to vent. ter’s sole function is to protect the solenoid valve
from water and oil, which could adversely affect
6. Close the bleeder valve. the solenoid valve’s performance. The coalescing
7. Release the service brake pedal. filter is equipped with an automatic drain.
8. Repeat procedures 3., 4., 5. and 6. until a
bubble-free flow of fluid is observed while con-
15-10 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

COALESCING
FILTER
SOLENOID
VALVE
BREATHER
INDICATES AIR FLOW
Illustration 15-9. Air Horn Components
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15-11

Brake Control (Air) System Troubleshooting
1. No brakes or weak 1. Empty or low brake reservoir. 1. Fill brake reservoir to the proper
brakes level with the specified fluid (refer
to the Fuel and Lubricant Specifi-
cations).
2. Air in brake system. 2. Bleed the brake system (refer to
Wet Disc Brake Bleeding in this
section).
3. Leak in the line between the 3. Inspect hydraulic hoses and repair
brake reservoir and the power clus- if needed.
ter.
4. Leak in line between the power 4. Inspect hydraulic hoses and repair
cluster and brake housings. if needed.
5. Defective piston seals. 5. Refer to the Rockwell Axle manual
for isolation of defective piston
seals (which side) and repairs.
6. Low air supply. 6. Refer to Problems 3. and 4. in this
7. Defective power cluster seals. 7. Replace power cluster seals.
8. Worn or damaged disc(s) inside 8. Refer to the Rockwell Axle manual
brake housing. for repairs.
9. Brakes are overheating. 9. Refer to Problem 1. of the Wet
Disc Brakes Cooling System
15C.
10. Defective brake relay valve. 10. Replace brake relay valve.
2. Brakes will not 1. Defective left or right service brake 1. Replace left or right service brake
release valve. valve.
2. Worn or damaged disc(s) in brake 2. Refer to the Rockwell Axle manual
housing. for repairing procedures.
3. High pressure brake-apply port of 3. Remove blockage from the high
the brake housing is blocked (the pressure brake-apply port of the
same port the power cluster forces brake housing.
the hydraulic oil through to move Loosen the bleeder valve to allow
the piston in the brake housing is trapped oil to escape. Remove the
the same port used to expel the oil high pressure brake-apply hose
from the brake housing). from the brake housing. Then with
a paper clip, insert a paper clip in
the port to remove the blockage,
reassemble and perform the Wet
Disc Brake Bleeding procedures
located in this section.
15-12 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

3. Low air pressure 1. Misadjusted air governor. 1. Readjust the air governor for the
(no air operated proper pressure (refer to the Air
components acti- Governor in this section for adjust-
vated) ment procedures).
2. Air leak in air system. 2. Check all connections and hoses
for leaks. Repair as required.
3. Drain valve of air tank is not fully 3. Ensure that the drain valve fully
closed or defective. closes and is sealing off the air
tank. Replace drain valve if
required.
4. Tripped or defective safety relief 4. Reset or replace safety relief valve
valve. as required.
5. Defective left or right service brake 5. Replace left or right service brake
valve. valve.
6. Defective parking brake valve. 6. Replace parking brake valve.
4. Low air pressure 1. Defective left or right service brake 1. Replace left or right service brake
(with an air oper- valve. valve.
ated component
2. Defective quick release valve. 2. Replace quick release valve.
activated)
3. Defective air seals in the power 3. Replace the air seals of the power
cluster. cluster.
4. Defective parking brake valve. 4. Replace parking brake valve.
5. Defective parking brake chamber. 5. Replace parking brake chamber.
6. Defective seals in the air inching 6. Replace the air inching cylinder.
cylinder.
5. Noisy brakes 1. Wrong type of hydraulic fluid is 1. Use the approved fluid (refer to the
being used. Fuel and Lubricant Specifica-
tions).
2. Brakes are overheating. 2. Refer to Problem 1. of the Wet
Disc Brakes Cooling System
15C.
3. Internal failure inside the wheel 3. Refer to the Rockwell Axle manual
end. for repairs.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15-13

15-14 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)
Illustration 15-10. Brake Control Circuit
LEFT HUB RIGHT HUB

BRAKE RESERVOIR
BRAKE
PARK BRAKE RELAY VALVE
LIGHT SWITCH
POWER
PARKING CLUSTER
BRAKE SHUTTLE
VALVE VALVE
OVERSTROKE
TO AIR SWITCH
PRESSURE
GAUGE PRESSURE
CHECK DE-CLUTCH
BREATHER
LOW AIR
SWITCH
LEFT
BRAKE RIGHT
VALVE BRAKE
(DE-CLUTCH) VALVE
TRANSMISSION
CONTROL VALVE
AIR HORN
COALESCING
CHECK GOVERNOR FILTER HORN
VALVE WIRE
SOLENOID
VALVE
SAFETY
(RELIEF)
VALVE BREATHER
AIR TANKS
DRAIN CUMMINS QSM11-C330 15-2461
VALVE DRAIN ENGINE
VALVE
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 15-15
15-16 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)
15C-Wet Disc Brakes
Cooling System
Section 15C
Wet Disc Brakes Cooling System

Introduction. The brake cooling system main- Auxiliary (Spreader / Brake) Pump (Illustration
tains a safe operating temperature by cooling the 22-8). The auxiliary pump, located on the back
hydraulic fluid in the wet disc brake system. side of the transmission (see Illustration 22-4), is a
tandem pump. It contains one 3/4” gear set that
Major Components (Illustration 15C-5). The
will supply 9 gpm of hydraulic fluid, at 2100 gov-
brake cooling system consists of an auxiliary
erned rpm, to the brake manifold valve and a 2”
(spreader / brake) pump, brake manifold valve,
gear set that will supply 24 gpm of hydraulic fluid,
hydraulic oil cooler, brake cooling valve, brake
at 2100 governed rpm, to the main attachment
cooling oil filter, various hoses and fittings. Com-
valve.
ponents of the brake cooling system can be
replaced individually. Refer to the Illustration 15-2 Brake Manifold Valve (Illustration 15C-5). The
for location and identification of parts. brake manifold valve, located on the left side of
the truck’s chassis (see Illustration 15-2), develops
BRAKE COOLER REMOTE CONTROLLER

PRESSURE CHECK PRESSURE CHECK
(BCA) (RCD)
PRESSURE SWITCH
(S23)
325 PSI
RELIEF
15 PSI
CHECK
400 PSI
REDUCER
175 PSI
RELIEF INDICATES BRAKE COOLING
FLUID FLOW
Illustration 15C-1. Brake Manifold Valve
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 15C-1
pilot pressure, protects the hydraulic controls and 4; its function is to ensure that anytime flow is
protects the oil cooler. It contains a 400 psi pres- present that the 10 psi, required to open pressure
sure reducer (in port 1) that ensures that the pilot switch (S23), can be obtained. Should the oil
pressure does not exceed 400 psi. The brake pressure drop below 10 psi from loss of flow, pres-
manifold valve also contains a 175 psi pressure sure switch (S23) will close, sending ground to the
relief (in port 3), ensuring minimum pilot pressure Brake Fail light (DS8), illuminating the light.
of at least 175 psi. It contains a 10 psi, normally
Hydraulic Oil Cooler (Illustration 15C-5). The
closed, pressure switch (S23, Illustration 15C-1) in
hydraulic oil cooler, located in front of the radiator
port B and a relief valve (in port 2) set for 325 psi.
(see Illustration 5-3), is forced-air cooled. Hydrau-
Should back pressure in the oil cooler circuit
lic fluid is circulated through its tubes and the fan
exceed 325 psi, the relief valve will open and
circulates air across the cooler and through the
relieve pressure to the hydraulic tank. The brake
fins, cooling the hydraulic fluid.
manifold valve also contains a 15 psi check in port
15 PSI CHECK
VALVES
BRAKE COOLING
PRESSURE
CHECK (BCC)
INDICATES BRAKE TEMPERATURE

COOLING FLUID FLOW SWITCH (S24)
Illustration 15C-2. Brake Cooling Valve
15C-2 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
Brake Cooling Valve (Illustration 15C-5). The
brake cooling valve, located above the differential Dispose of oil and filter in
of the drive axle, divides the flow equally to each accordance with federal and local regulations.
brake housing and monitors brake coolant temper-
ature. Nominally 9 gpm of hydraulic fluid will enter 1. Make certain filter is cool to the touch and pro-
the brake cooling valve. There are two modulat- vide a suitable container to catch any draining
ing orifices, internal to the valve, that will regulate oil.
and divide the flow of fluid equally to each brake 2. Apply an even film of fresh oil on the gasket
housing (4.5 gpm). In addition, there are two 15 surface of the replacement filter element.
psi check valves, located on the brake cooling
valve, that limit the wheel ends from seeing no 3. Unscrew filter and dispose of properly.
more than 15 psi of pressure, protecting the wheel 4. Thread the new filter onto filter head.
end face seals. The temperature switch (S24,
Illustration 15C-2), a normally open switch, will 5. Hand tighten filter element 3/4 turn past point
close when the oil temperature exceeds 190_F. where gasket first contacts filter head surface.
When the temperature switch (S24) closes, it will
provide ground to the Brake Fail light (DS8), illumi-
nating the Brake Fail light.
FILTER
HEAD
FILTER
ELEMENT
Illustration 15C-3. Brake Cooling Oil Filter
Changing The Brake Cooling Oil Filter Element

(Illustration 15C-3). The brake cooling oil filter ele-
ment (refer to Illustration 15-2 for location) should
be changed every six months or 1500 hours,
whichever comes first. The interval above is
based on normal environmental condition, exces-
sive dust may require a more frequent filter
change interval. Perform the following procedures
to change the filter element:
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15C-3

Wet Disc Brakes Cooling System Troubleshooting
1. Brakes Overheat 1. Low cooling fluid flow. 1. Refer to Problem 2. of this trouble-
shooting chart.
2. Improper hydraulic fluid. 2. Use specified fluid (refer to the
Fuel and Lubricant Specifica-
tions in the Appendices).
3. Oil cooler fins are restricted. 3. Clean the oil cooler or remove
restriction.
4. Excessive duty cycle (excessive 4. Allow hydraulic oil to cool and
application of brakes). adjust duty cycle.
5. Brakes at wheel ends are not fully 5. Refer to Problem 2. in the Brake
releasing. Control (Air) System Trouble-
shooting chart in Section 15.
6. Defective pressure relief valve (325 6. Replace the pressure relief valve
psi) in the brake manifold valve. (325 psi) in the brake manifold
Pressure relief valve is stuck open. valve.
7. Restriction in the brake cooling 7. Remove restriction from the brake
valve. cooling valve.
2. Low Cooling Fluid 1. Low hydraulic fluid supply. 1. Fill hydraulic tank to the proper
Flow fluid level.
2. Restricted suction strainer. 2. Replace auxiliary (spreader /
brake) pump.
3. Plugged breather filter(s). 3. Replace breather filter(s).
4. Air leak in suction hose to auxiliary 4. Locate leak and repair.
(spreader / brake) pump.
5. Defective auxiliary (spreader / 5. Replace the auxiliary (spreader /
brake) pump. brake) pump.
6. Restricted cooler core. 6. Replace cooler.
7. Restriction in the brake manifold 7. Remove restriction from the brake
valve. manifold valve.
3. One Side of Drive 1. Defective checks in brake cooling 1. Replace defective checks.
Axle Overheats valve.
2. Defective brake cooling valve. 2. Replace brake cooling valve.
15C-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 15C-4. Brake Cooling Circuit
15C-0080 SHT. 01
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 15C-5
Illustration 15C-5. Brake Cooling ANSI Circuit
15C-0080 SHT. 02
15C-6 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
7/05)
15D-Air Dryer
Section 15D
Air Dryer System

Introduction. In the air dryer system (if Air Dryer Operation and Leakage Tests. The
equipped), an air dryer collects and removes air following air dryer operation and leakage test pro-
system contaminates in solid, liquid, and vapor cedures should be performed every 3 months.
form before they enter the brake system. The air
1. Test the outlet port check valve assembly by
dryer provides clean, dry air to the components of
building the air system to governor cut-out and
the brake system which increases the life of the
observing a test air gauge installed in the air
system.
tank. A rapid loss of pressure could indicate a
Major Components (Illustration 15D-3). The air failed outlet port check valve. This can be
dryer system consists of an air dryer, wire har- confirmed by bleeding the system down,
ness, and hoses. removing the check valve assembly from the
end cover, subject air pressure to the unit and
Changing the Desiccant Cartridge. The desic-
apply a soap solution to the check valve side.
cant cartridge should be changed every 3 years.
Leakage should not exceed a 1 inch bubble in
The desiccant change interval may vary. Although
1 second.
typical desiccant cartridge life is 3 years, many will
perform adequately for a longer period of time. In 2. Check for excessive leakage around the purge
order to take maximum advantage of desiccant life valve. With the compressor in loaded mode
and assure that replacement occurs only when (compressing air), apply a soap solution to the
necessary, it is important that the “Air Dryer purge valve housing assembly exhaust port. If
Operation and Leakage Tests” procedures be per- the leakage exceeds a 1” bubble in 1 second,
formed. service the purge valve housing assembly.
NOTE: A small amount of oil in the system may 3. Close reservoir drain valve. Build up system
be normal and should not, in itself, be considered pressure to governor cut-out and note that
a reason to replace the desiccant; oil stained des- AD-9 purges with an audible escape of air.
iccant can function adequately. “Fan” the service brakes to reduce system air
pressure to governor cut-in. Note that the sys-
Air Dryer Inspection. The following should be tem once again builds to full pressure and is
checked every 3 months to maintain proper opera- followed by an AD-9 purge.
tion of the air dryer. 4. Check the operation of the safety valve by
1. Check for moisture and the presence of water pulling the exposed stem while the compres-
in the air brake system by opening the drain sor is loaded (compressing air). There must
valve, located on the bottom of air tank. If be an exhaust of air while the stem is held and
moisture is present, the desiccant cartridge the valve should reseat when the stem is
may require replacement; however, the follow- released.
ing conditions can also cause water accumula- 5. Check all lines and fittings leading to and from
tion and should be considered before replac- the air dryer for leakage and integrity.
ing the desiccant.
6. Check the operation of the end cover heater
a. An outside air source was used, bypassing and thermostat assembly during cold weather
the air dryer. operation as follows:
b. In areas where more than a 30 degree
range of temperature occurs in one day, a. Electric Power to the Dryer. With the
small amounts of water can accumulate in ignition or engine kill switch in the On posi-
the air brake system due to condensation. tion, check for voltage to the heater and
Under these conditions, the presence of thermostat assembly using a voltmeter or
small amounts of moisture is normal and test light. Unplug the electrical connector
should not be considered as an indication at the air dryer and place the test leads on
that the dryer is not performing properly. each of the pins of the male connector. If
there is no voltage, look for a blown fuse,
2. Check mounting bolts for tightness. Re-torque
broken wires or corrosion in the vehicle
bolts to 23 - 32 ft-lbs. if necessary.
wiring harness. Check to see if a good
ground path exists.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15D-1

b. Thermostat and Heater Operation. Turn Warm the end cover assembly to over
off the ignition switch and cool the end 90_F and again check the resistance. The
cover assembly to below 40_F. Using an resistance should exceed 1000 ohms. If
ohmmeter, check the resistance between the resistance values obtained are within
the electrical pins in the female connector. the stated limits, the thermostat and heater
The resistance should be 1.5 to 3.0 ohms assembly is operating properly. If the
for the 12 volt heater assembly. resistance values obtained are outside the
stated limits, replace the purge valve hous-
NOTE: Some early models of the AD-9 will have ing assembly which includes the heater
resistance readings of 1.0 to 2.5 ohms for the 12 and thermostat assembly.
volt heater assembly. If the resistance is higher
than maximum stated, replace the purge valve
housing assembly which includes the heater and
thermostat assembly.
DESICCANT
CARTRIDGE
AIR DRYER
DISCHARGE
HOSE
INDICATES AIR FLOW
Illustration 15D-1. Air Dryer Components Identification
15D-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Air Dryer Troubleshooting
1. Dryer is constantly 1. Excessive leakage in fittings, 1. Using soap solution, test for leak-
“cycling” or purging. hoses, and tubing connected to the age all fittings, drain valve (if any)
compressor, air dryer, and first res- and safety valve in first reservoir.
ervoir. Repair or replace as necessary.
2. Defective check valve assembly in 2. Remove check valve assembly
AD-9 air dryer end cover. from end cover. Subject air pres-
sure to delivery side of valve.
Apply soap solution at opposite
end and check for leakage. (Per-
missible leakage - 1” bubble in five
seconds.) If excessive leakage,
replace check valve assembly.
3. Defective governor. 3. Test governor for proper cut-in and
cutout pressures and excessive
leakage in both positions.
4. Leaking purge valve housing 4. With the supply port open to atmo-
assembly and / or O-rings in AD-9 sphere, apply 120 psi at the control
air dryer end cover. port. Apply a soap solution to the
supply port and exhaust port
(purge valve seat area). Permissi-
ble leakage - 1” bubble in five
seconds.
5. Compressor unloader mechanism 5. Remove air strainer or fitting from
leaking excessively. compressor inlet cavity. With com-
pressor unloaded, check for
unloader piston leakage. Slight
leakage permissible.
6. Rapid cycling of the governor due 6. With gauge installed at RES port of
to air starvation at the RES port of governor, pressure should not drop
the governor. below “Cut-in” pressure at the
onset of the compressor
“Unloaded” cycle. If pressure
drops, check for “kinks” or restric-
tions in line connected to RES port.
Line connected to RES port on
governor must be same diameter,
or preferably larger than, lines con-
nected to UNL port(s) on governor.
2. Water in vehicle. 1. Desiccant requires replacement - 1. Replace desiccant cartridge.

excessive contaminants in desic-
cant cartridge assembly.
continued
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15D-3

2. Water in vehicle. 2. Air system charged from outside air 2. If system must have outside air fill
(Continued) source (outside air not passing provision, outside air should pass
through air dryer). through air dryer. This practice
should be minimized.
3. Air dryer not purging (see Problem 3. See cause and correction for Prob-
5.). lem 5.
4. Purge (air exhaust) time insufficient 4. Check causes and corrections for
due to excessive system leakage Problem 1.
(see causes for Problem 1.).
5. Air by-passes desiccant cartridge 5. Replace desiccant cartridge / end
assembly. cover O-ring.
Check to make sure desiccant car-
tridge assembly is properly
installed.
6. Purge time is significantly less than 6. Replace desiccant cartridge / end
minimum allowable. cover O-ring.
Check to make sure desiccant car-
tridge assembly is properly
installed.
Replace desiccant cartridge
assembly.
3. Safety valve on air 1. Desiccant cartridge plugged. 1. Check compressor for excessive oil
dryer “popping off” or passing and / or correct compres-
exhausting air. sor installation. Repair or replace
as necessary. Rebuild or replace
cartridge.
2. Defective discharge check valve in 2. Test to determine if air is passing
end cover of the AD-9. through check valve. Repair or
replace.
3. Defective fittings, hose, or tubing 3. Check to determine if air is reach-
between air dryer and first reser- ing first reservoir. Inspect for kinked
voir. tubing or hose. Check for undrilled
or restricted hose or tubing fittings.
4. Safety valve setting lower than the 4. Reduce system pressure or obtain
maximum system pressure. a higher setting safety valve.
15D-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

4. Constant exhaust 1. Air dryer purge valve leaking 1. With compressor loaded, apply
of air at air dryer excessively. soap solution on purge valve
purge valve exhaust exhaust, to test for excessive leak-
or unable to build age. Repair purge valve as
system pressure. necessary.
(Charge mode) 2. Defective governor. 2. Check governor for proper “cut-in,”
“cutout” pressure and excessive
leakage in both positions. Repair
or replace as necessary.
3. Purge control line connected to 3. Purge control line must be con-
reservoir or exhaust port of gover- nected to unloader port of gover-
nor. nor.
4. Purge valve frozen open - faulty 4. Test heater and thermostat.
heater and thermostat, wiring,
blown fuse.
5. Inlet and outlet air connections 5. Compressor discharge to inlet port.
reversed. Reconnect lines properly.
6. Kinked or blocked (plugged) dis- 6. Check to determine if air passes
charge line. through discharge line. Check for
kinks, bends, and / or excessive
carbon deposits.
7. Excessive bends in discharge line 7. Discharge line should be constant-
(water collects and freezes). ly sloping from compressor to air
dryer with as few bends as pos-
sible.
8. Excessive system leakage. 8. See Problem 1.’s Causes and
Corrections.
9. Purge valve stays open - supply air 9. Replace purge valve housing
leaks to control side. assembly O-rings.
5. Air dryer does not 1. Broken, kinked, frozen, plugged, or 1. Test to determine air flows through
purge or exhaust air. disconnected purge control line. purge control line when compres-
sor unloaded. Check for undrilled
fittings. (see Problem 4., Correction
3.)
2. See Causes 2., 5., and 7. for Prob- 2. Refer to Corrections 2., 5., and 7.
lem No. 4. for Problem 4.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 15D-5

6. Desiccant material 1. This problem is almost always 1. See Causes and Corrections for
being expelled from accompanied by one or more of Problems 1., 2., 3., 4., and 5.
air dryer purge valve Problems 1., 2., 3., 4., and 5. See
exhaust (may look related causes for these problems
like a whitish liquid, above.
paste, or small 2. Air dryer not securely mounted. 2. Vibration should be held to a mini-
beads). (Excessive vibration) mum. Add bracket supports or
or change air dryer mounting location
Unsatisfactory if necessary.
desiccant life.
3. Defective cloth covered perforated 3. Replace desiccant cartridge
plate in air dryer. assembly.
4. Compressor passing excessive oil. 4. Check for proper compressor
installation; if symptoms persist,
replace compressor.
5. Desiccant cartridge not assembled 5. Check the torque on the desiccant
properly to end cover. (Loose cartridge to end cover attachment.
attachment) Refer to assembly section of this
data sheet.
7. Constant seepage 1. Defective check valve assembly in 1. Refer to Correction 3. of Problem 1.

of air at air dryer AD-9 air dryer and cover.
purge valve exhaust
(non-charging
mode).
8. The air dryer 1. Compressor fails to “unload.” 1. Faulty governor installation; no air
purge piston cycles line from governor to compressor
rapidly in the com- or line is “kinked” or restricted.
pressor unloaded Install or repair air line.
(non-compressing)
mode.
15D-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 15D-3. Air Dryer Circuit
AIR DRYER
DISCHARGE
HOSE
GOVERNOR
10 AMP
FUSE
15D-0029
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 15D-7
1-12 RTGP-9042N (9/01)
Section 16
Steering System
Introduction. The steering system provides guid- not being used, will supply the main control valve.
ance control of the truck. The steering circuit has This gear set is the sole source of hydraulic fluid
priority over hydraulic fluid flow. for the tilt section. The other gear set supplies
hydraulic fluid to the lift section only. The pres-
Major Components (Illustration 16-3). The steer-
sure of the steering / tilt gear set can be checked
ing system consists of the main pump, steer sens-
at pressure check (PC1). The pressure of the
ing valve, steering valve, steer cylinder, hoses and
second gear set, dedicated to the lift section, can
various fittings.
be checked at pressure check (PC2). See Illustra-
Main Pump (Illustration 16-4). The main pump is tion 22-4 for both pressure check locations.
a tandem gear pump that provides hydraulic fluid
Steer Sensing Valve (Illustration 16-4). The steer
flow to operate the hydraulic circuit. When the
sensing valve, located on the left inboard side of
pump is turned, it creates a vacuum at the pump
the chassis in front of the transmission (see
inlet which allows atmospheric pressure to force
Illustration 22-1), provides the logic for the steer-
hydraulic fluid through a suction strainer in the
ing circuit. It is linked to the steering valve and
tank into the inlet line of the pump. The pump
main pump. When the steering valve is turned,
then mechanically pushes this fluid to its outlet
pressure in a load sense line increases, between
port for use in the hydraulic circuit.
the steering valve and steer sensing valve, shift-
The main pump has two sections, each containing ing the spool of the steer sensing valve, directing
a pumping gear set. Each pumps at a maximum a flow of fluid from the main hydraulics to the
rate of 62 gpm at 2100 governed rpm. One of the steering valve. The steer sensing valve also con-
gear sets is dedicated to the steering circuit. It tains a 2500 psi steer circuit relief valve. To trou-
supplies fluid to the steer sensing valve and will bleshoot the steer sensing valve, refer to Steer
supply the main control valve when not steering. Sensing Valve of the Troubleshooting The
When steering, the gear set will supply only the Major Components in Section 22.
amount of fluid required to steer. The excess flow,
STEER RELIEF
VALVE SET SCREW
STEER RELIEF VALVE
Illustration 16-1. Steer Sensing Valve
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 16-1

1. STEERING COLUMN
2. STEERING VALVE
3. STEER CHECK
VALVE (SCV)
Illustration 16-2. Steering Components
Steering Valve (Illustration 16-2). The steering

valve, located on the base of the steering column,
directs and meters the flow of hydraulic fluid to the
steer cylinder depending on which way and how
fast the steering valve is turned.
Steer Cylinder (Illustration 16-4). The steer cylin-
der is a double-acting cylinder that turns the steer
tires.
Setting Hydraulic Pressures. Refer to Setting
Hydraulic Pressures in Section 22 for proce-
dures to set the pressures for the steer sensing
valve.
16-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Steering System Troubleshooting (Illustrations 16-3 and 16-4)
1. Slow or Hard 1. Limited hydraulic fluid flow. 1. Refer to Problem 6. in this trouble-
Steering shooting chart.
2. Low steering pressure. 2. Refer to Problem 7. in this trouble-
shooting chart.
3. Hydraulic fluid is bypassing the 3. Repack steer cylinder.
steer cylinder piston packing.
4. Spool in the steer sensing valve is 4. Remove spool, then visually
sticking. inspect spool and spool housing for
debris.
5. Defective steer sensing valve. 5. Repair or replace steer sensing
valve.
6. Steering cylinder rod bent. 6. Replace cylinder rod or cylinder.
7. Defective steering valve. 7. Replace steering valve.
8. Load sense line from steering 8. Remove restriction.
valve to steer sensing valve is
restricted.
2. No Response 1. Low hydraulic fluid flow. 1. Refer to Problem 6. in this trouble-

When Steering shooting chart.
Wheel is Turned
2. Hydraulic fluid is bypassing the 2. Repack steer cylinder.
steer cylinder piston packing.
3. Incorrect steering relief valve pres- 3. Set steer relief valve pressure for
sure setting. correct pressure.
4. Defective steering relief valve. 4. Replace steering relief valve.
5. Spool in the steer sensing valve is 5. Remove spool, then visually
sticking. inspect spool and spool housing for
debris.
6. Defective steer sensing valve. 6. Repair or replace steer sensing
valve.
7. Steering cylinder rod bent. 7. Replace steering cylinder.
8. Defective steering valve. 8. Replace steering valve.
9. Load sense line from steering 9. Remove restriction.
valve to steer sensing valve is
restricted.
3. Steering Tires Do 1. Binding in linkage. 1. Re-align linkage.

Not Track with
Steering Wheel 2. Broken centering springs in steer- 2. Replace centering springs.
ing valve.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 16-3

4. Wrong Response 1. Hoses to ports in steering valve are 1. Reconnect in the correct hose
to Steering Wheel crossed. layout.
5. Continuous Steer- 1. Defective steering valve. 1. Replace steering valve.

ing Wheel Rotation
2. Defective steer column. 2. Replace steer column.
3. Hydraulic fluid bypassing steer cyl- 3. Repack the steer cylinder.
inder piston packing.
4. Loose or broken hydraulic hose 4. Tighten or replace hydraulic hose.
between steering valve and steer
cylinder.
6. Limited Hydraulic 1. Clogged suction strainer. 1. Clean suction strainer.

Fluid Flow
2. Low hydraulic fluid supply. 2. Fill tank to the correct fluid level.
3. Incorrect type of fluid. 3. Drain and flush hydraulic circuits.
Use the specified hydraulic fluid.
4. Cold hydraulic fluid. 4. Due to extended periods of cold
temperatures, the viscosity of the
hydraulic fluid can increase. Con-
sider adding a cold weather
package.
5. Breather filter stopped up. 5. Replace the breather filter.
6. Worn / defective main / steering 6. Replace or rebuild pump.
pump.
7. Low Steer Pres- 1. Incorrect steer relief valve pressure 1. Adjust steer relief valve for correct
sure setting. pressure.
2. Defective steering relief valve. 2. Replace steering relief valve.
3. Limited hydraulic fluid flow. 3. Refer to Problem 6. in this trouble-
shooting chart.
4. Defective seal in the steer cylinder. 4. Repack steer cylinder.
5. Defective steer sensing valve. 5. Repair or replace steer sense
valve.
8. Kick-back in Steer- 1. Defective steering check valve 1. Replace steering check valve
ing Wheel (SCV). (SCV).
16-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 16-3. Steering Circuit
STEER
VALVE
STEER
SENSE
VALVE MAIN LIFT / TILT
VALVE
HYDRAULIC
TANK
MAIN
PUMP
16-2274 SHT. 01
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 16-5

Illustration 16-4. Steering ANSI Circuit
16-2274 SHT. 02
16-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Section 17
Tires and Wheels

Introduction. This section contains safety warn- Tire Inflation. The tire pressure should be
ings that must be adhered to, to prevent serious checked on a daily basis (refer to the serial data
personal injury or death when servicing tires and plate, located on the left side of the truck in front
wheels. Also included are procedures for properly of the steer tire, for proper tire pressure).
torquing the wheel nuts.

Maintain the proper tire

Under no circumstances inflation pressures listed on the truck serial
should anyone mount or demount tires without data plate.
proper training as required in OSHA Rules and
Regulations 1910.177 “Servicing multi-piece Tire Overinflation. Overinflation results in high
and single piece rim wheels.” Follow all pro- cord stress even when the tire isn’t overloaded.
cedures and safety instructions. Stress reduces resistance to blowouts from
impacts. It also increases the danger of the tire
Tires. Tires may represent one of the major direct being cut. The problem can be compounded by
expenses of equipment operation. Refer to the poorly maintained working terrain.
Goodyear Tire Maintenance Manual for proper
Tire Underinflation. An underinflated tire will
maintenance and repair of tires for optimal tire life.
deflect too much. It also leads to excessive side-
The Goodyear Tire Maintenance Manual is a
wall flexing. It is very important, in wheel ends
generic tire maintenance manual covering tire
employing dual tire pairs, that each tire have the
maintenance that apply to all brands of tires.
correct air pressure. This prevents one tire from
Check the tires and valve caps daily for any dam-
carrying more of the load than the other tire. Flex-
age.
ing of an underinflated tire in a dual pair could
lead to the underinflated tire rubbing the other tire

which could lead to premature tire failure. Tires
S All tire related safety warnings in the Safety with radial cracks indicate continuous underinfla-
Check booklet and this section must be tion operation. Other underinflated indications
understood before performing any tire main- include the following:
tenance. 1. Spotty or uneven tread wear
S Never sit on or stand in front of a tire and rim 2. Ply separation
assembly that is being inflated. Use a clip-
on chuck and make sure the inflation hose is 3. Loose or broken cords inside the tire
long enough to permit the person inflating 4. Fabric carcass fatigue
the tire to stand to the side of the tire, not in
front or in back of the tire assembly. Rims. The rims hold the tires on the hub. The
wheels and mounts require a run-in period. The
S Keep tires free of grease and oil. Grease
torque of the wheel nuts must be checked every
and oil are highly damaging to tires. If
10 hours of operation until rim is fully seated. Per-
grease or oil are allowed to remain on tires
form the Torquing Procedure to tighten the
for extended periods of time, rubber deterio-
wheel nuts of each hub each time tires are
ration may occur.
removed from the drive or steer axle. Inspect the
S Tire assemblies operated as a dual pair must wheel studs daily.
have the same outside diameter, be from the
same manufacturer, be of the same type
(industry code) and be of the same construc-
If one wheel stud has broken
tion (both bias or both radials). off, some of the rim’s clamping force will be
S Bias and radial constructions must never be lost. Remove machine from service and repair
mixed on dual pair. immediately.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 17-1

WHEEL NUT TORQUE VALUE[
Drive Axle:
PRC-7534........330 - 350 ft-lbs
[ This value is located on the truck 24 1 17
serial plate for reference. 12 26
20 7
5 28
18 11
8 23
14 3
4 15
22 9
10 19
6
21
27 13
16 2 25
Illustration 17-1. Drive Axle Wheel Nuts Torquing Sequence

Torquing Procedure (Illustrations 17-1 and 17-2). been applied to each wheel nut. Procedure 1.
Perform the following procedures to torque the may have to be repeated several times to
wheel nuts: tighten the wheel nuts to the proper torque
value.

Every time the wheels are Inspection
removed, a run-in period is required. The
wheel nuts must be re-torqued every 10 hours

of operation until rims are fully seated.
S Mixing parts of one manufacturer’s rims with
1. Start at position #1 and tighten the wheel nut those of another is potentially dangerous.
to the specified torque value listed in Illustra- Always check manufacturer for approval.
tion 17-1 or 17-2. Proceed in the illustrated S Do not be careless or take chances. If you
numerical order to torque the other wheel are not sure about the proper mating of rim
nuts. and wheel parts, consult a wheel and rim
expert. This may be the tire man who is
2. Repeat procedure 1. until none of the wheel servicing your fleet or the rim and wheel
nuts move and the proper torque value has distributor in your area.
17-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

WHEEL NUT TORQUE VALUE[
Steer Axle.............145 - 155 ft-lbs
[ This value is located on the truck
serial plate for reference. 1
14 15
7 5
9 12
4 3
11 10
6 8
13
2
Illustration 17-2. Steer Axle Wheel Nuts Torquing Sequence

1. Check rim components periodically for fatigue Tire / Wheel Jacking
cracks. Replace all cracked, badly worn, dam-
aged, and severely rusted components. Use a
wire brush to remove dirt and rust if necessary.

S Never rely solely upon jacks or hoists to
2. Clean and repaint rims to stop detrimental support the lift truck while removing tire /
effects of corrosion. Be very careful to clean wheel.
all dirt and rust from the lock ring gutter. This
is important to secure the lock ring in its proper S Before placing jack in position, block tire
position. Using air inflation equipment, and wheel on the other side of the truck.
equipped with a filter, helps remove moisture S Always place oak or other hardwood block
from the air line, preventing some corrosion. cribbing under the load after the jack or
hoist has lifted the load. Make sure the crib-
3. Ensure that the correct parts, that match your
bing is large enough to have sufficient con-
type of wheels, are being used in assembly.
tact with the supported load to be stable.
Check with manufacturer if you have any
doubts. S Never get under, near or between heavy
objects that are supported only by a jack or
hoist.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 17-3

S Always use hardwood blocks under jack. ing inflation. Misassembled parts may fly
apart with explosive force during inflation.
Demounting
S Do not seat rings by hammering while the
tire is being inflated. If a part is tapped, it or

the tool can fly out with explosive force.
S Do not let anyone mount or demount tires S Never sit on or stand in front of a tire and rim
without proper training as stated in OSHA assembly that is being inflated. Use a clip-
Rules and Regulations 1910.177 “Servicing on chuck and make sure the inflation hose is
multi-piece and single piece rim wheels.” long enough to permit the person inflating
S Do not stand in front of the tire during the tire to stand to the side of the tire, not in
deflation. front or in back of the tire assembly.
S Demounting tools apply pressure to rim S Mixing parts of one manufacturer’s rims with
flanges to unseat tire beads. Keep your those of another is potentially dangerous.
fingers clear. Slant the demounting bead Always check manufacturer for approval.
tool about 10° to keep it firmly in place. If it S Do not be careless or take chances. If you
slips off, it can fly with enough force to kill. are not sure about the proper mating of rim
Always stand to one side when you apply and wheel parts, consult a wheel and rim
hydraulic pressure. expert. This may be the tire man who is
S Never force or hammer rim components, servicing your fleet or the rim and wheel dis-
especially rim components under pressure. tributor in your area.
S Never attempt to weld on an inflated tire / rim S Do not inflate the tire before all side and lock
assembly. rings are in place. Double check to make
S Do not under any circumstances, attempt to sure all components are properly seated.
rework, weld, heat or braze any rim compo- 1. Refer to Illustration 17-3 for hardware and its
nents that are cracked, broken, or damaged. orientation for wheel mounting.
Replace with new parts, or parts that are not
cracked, broken, or damaged, and which are 2. Check components for proper assembly again
of the same size, type and make. after inflating to approximately 5 psi (34.47 kPa).
S Do not hammer on rims or components with Operation
steel hammers. Use rubber, lead, plastic, or
brass faced mallets, if it is necessary, to tap
components together.

S Do not overload rims or over-inflate tire / rim
S Always exhaust all air from a single tire and assembly. Check your rim manufacturer if
from both tires of a dual assembly prior to special operating conditions are required.
removing any rim components such as nuts
and rim clamps. S Do not use undersized rims. Use recom-
mended rim for the tire.
S Make sure to remove the valve core to
exhaust all air from the tire. Remove both S Never run a vehicle on one tire of a dual
cores from a dual assembly. assembly. The carrying capacity of the
single tire and rim is dangerously exceeded
S Check the valve stem by running a piece of and operating a vehicle in this manner can
wire through the stem to make sure it is not result in damage to the rim and tire.
plugged.
S Do not reinflate a tire that has been run flat
Mounting And Inflation without first inspecting the tire, rim and
wheel assembly. Double check the lock ring
for damage; make sure that it is secure in

the gutter before inflation.
S Inflate tire in a safety cage. Use safety
chains or equivalent restraining devices dur- S Excessive turning of the steering axle tires,
when the truck is stopped, should be
17-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

avoided. It can cause excessive wear (flat S Do not use alcohol, methanol, or other
spots) to develop. flammable agents in the compressor to pre-
Servicing Tire And Rim On Vehicle vent freezing of the condensation inside the
compressor. Drain the compressor tank
frequently or locate the compressor inside to

eliminate the freezing problem.
S Block the other tires of the vehicle before S Do not locate the compressor near a battery
you place the jack in position. charger. Batteries emit hydrogen gas, which
S Regardless of how hard or firm the ground is highly flammable, during the charging pro-
appears, put hardwood blocks under the cess, and could be sucked into the compres-
jack. Always crib up vehicle with blocks just sor intake.
in case the jack should slip.
S Remove the bead seat band slowly to pre-
vent it from dropping off and crushing your
toes. Support the band on your thigh and
roll it slowly to the ground. This will protect
your back and toes.
S When using a cable sling, stand clear; it
might snap and lash out.
Compressor Precautions
There have been instances of tires exploding vio-
lently while on vehicles. The forces involved in
this type explosion are sufficient enough to cause
serious personal injury to anyone in the immediate
vicinity. Some of these explosions are believed to
have been caused by flammable vapors entering
the tire during inflation. When the machine is
operating, the temperature of the air and vapor
mixture inside the tire will increase. The tempera-
ture inside the tire will also increase with an
increase in ambient temperature and when sub-
jected to direct sunlight. If the vapor and air mix-
ture inside the tire are within the ratio limits that
will support combustion, and any or all of the
above heat increasing factors cause the tempera-
ture to rise, an explosion may occur. The follow-
ing are some warnings that can prevent flam-
mable vapors from entering the compressor and
subsequently being entrapped in tires.

S Do not locate the compressor in a utility
room used for storing flammable solvents,
paints, thinners, etc. The flammable vapors
will be sucked into the compressor intake
while the compressor is charging.
S Do not clean the compressor air filter with a
flammable solvent. Use a non-flammable
solvent, such as carbon tetrachloride.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 17-5

1. DRIVE AXLE
2. RIM
8 3. SPACER
4. WEDGE RING
9 5. NUT
6. LOCKWASHER
7. WHEEL CLAMP
9 8. RIM
9. FLANGE
10. O-RING
11. BEAD SEAT BAND
12. LOCK RING
11
10
12
3 7
NOTE: TO OPERATOR
5
Wheel and mounts require run in period on a
new machine and after each tire change. 2
Refer to serial plate on the side of machine for
torque specifications before machine is put in
service and re-torque nuts each 10 hours until 4 6
clamps are seated.
Care should be taken to keep grease and other

foreign material from rim seating surfaces.
Illustration 17-3. Wheel Mounting Hardware and Tightening Procedures
17-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Section 18
Chassis
Introduction (Illustration 18-1). The chassis is hangers, drive axle mounts, tilt cylinder anchors
carefully engineered and ruggedly constructed. and steer axle mounts.
Welded steel structures always contain undetect-
able cracks, especially welded joints. When these
joints are subject to fluctuating stresses of signifi-

cant magnitude, these cracks will grow. This is S Periodic inspection is required to detect
known as fatigue crack growth. No matter how fatigue cracks that have grown to a signifi-
low the stress levels are kept, some fatigue crack cant size in order to avoid serious failure of
growth will occur in all welded structures. the structural weldment. When a crack is
found, the truck must be immediately taken
Structural Inspection and Reporting Procedure out of service and repaired.
(Refer to SIRR in the Appendices). Follow the
OSHA rules, 29 CFR, 1910.178 (Q)(1), (5), & (7) S Under no circumstances, without prior
which require inspecting industrial trucks daily approval from Taylor Machine Works, Inc.
before being placed in service, removing trucks Engineering Department, should the chassis
from service if cracks are found, and making be modified, i.e. adding of additional coun-
repairs only if authorized by the manufacturer. If terweights. As per OSHA 29 CFR1910.178
trucks are used on a round-the-clock basis, they (a) (4).
shall be examined after each shift. OSHA 29 CFR S If the fatigue crack is allowed to grow, cata-
1910.178 (p)(1) requires that trucks in need of strophic failure could occur in the chassis or
repair be taken out of service. Areas to be other welded components, causing serious
inspected on the truck chassis include mast injury to personnel and / or property.
Chassis Troubleshooting
1. Cracks in welds 1. Metal fatigue. 1. Have cracks in welds repaired

(Refer to SIRR in the immediately.
Appendices) 2. Overloading. 2. Refer to Correction 1. above and
Notify Taylor avoid overloading the truck.
Machine Works, 3. Rough terrain. 3. Refer to Correction 1. above and, if
Inc. for proper possible, avoid operating truck on
repair procedures. rough terrain.
4. Travelling with load in an unrecom- 4. Refer to Correction 1. above and
mended travel position (excessive the Operator’s Guide for proper
height and / or fully side-shifted, travelling positions.
one side or the other).
5. Severe duty cycles. 5. Have cracks in welds repaired
immediately.
2. Engine support 1. Engine vibration. 1. Refer to Problem 23. in the Engine

mounts broken Troubleshooting chart in Section
1.
2. Transmission vibration. 2. Refer to Problem 9. in the Trans-
mission Troubleshooting chart in
Section 9.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 18-1

3. Transmission sup- 1. Transmission vibration. 1. Refer to Problem 9. in the Trans-

port mounts bro- mission Troubleshooting chart.
ken
2. Engine vibration. 2. Refer to Problem 23. in the Engine
1.
4. Hinged doors are 1. Door hinges are not properly 1. Lubricate door hinges.
difficult to open lubricated.
18-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Note: Photocopy this sketch to identify fatigue cracks or
structural damage to the chassis. Be very descriptive of
damage to the chassis, i.e. location, depth, length.
Illustration 18-1. Chassis
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 18-3

1-12 RTGP-9042N (9/01)
Section 20
Cab
Illustration 20-1. Cab

Introduction (Illustration 20-1). The cab has 7. The tilt steering must lock firmly into position.
been carefully designed with the operator’s safety
and comfort in mind. The components in the cab
have been laid out for easy access.

S Failure to adhere to any of the above could
Cab Maintenance Checks. The following checks lead to personal injury, death or property
must be performed before operating the truck. damage.
1. Steps and operator’s compartment must be S Avoid stepping on the top Lexan cover while
free of oil, grease and trash. servicing the truck.
2. All glass and mirrors of the cab should be S Always use OSHA approved ladders, stands,
cleaned daily to keep vision from being or manlifts to reach high places on the truck.
impaired. S The top Lexan cover is a part of the OSHA
3. Under no circumstance should objects be mandated FOPS (Falling Object Protective
allowed in the cab which would restrict the Structure). Do not remove or replace cover
operator’s vision or exit. with glass.
4. The seat must lock firmly into position. Troubleshooting
5. The seat belt must always be intact and 1. Should abnormal vibration or shifting of cab
operable. structure occur, check mounting bolts for tight-
ness and ensure that rubber mounts are not
6. The door latch must always function properly. damaged.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05) 20-1

06/03)
2. Should leak occur from the seals of the
glasses, repair seal.
Lubrication. The grease fittings, on the door
hinges, should be greased monthly or every 250
hours, whichever comes first.
20-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

20A-Air Conditioning
System
Section 20A
Air Conditioning System

Introduction. The air conditioning / heating sys- NOTE: Any time repairs are made to the air con-
tem provides the operator with a comfortable ditioning system which require the recovery of the
operating environment. Provided all shut-off val- refrigerant, it is recommended that the drier be
ves are open when the engine coolant tempera- changed and 4 ounces of AC ester lubricating oil
ture opens the thermostat, heated coolant flows be added to the dryer.
from the engine block through the heater coils,
through the heater shut-off valve, through the Condenser. The condenser changes the refriger-
heater coil of the air conditioner / heater unit, ant from a hot, high pressure gas (from the com-
through the defroster, and returns back to the pressor) to a warm, high pressure liquid (to the
water pump. drier) by cooling the refrigerant. The condenser is
powered by 12 VDC from a 20 amp circuit breaker
Major Components (Illustrations 20A-2 and (CB26).
20A-3). The air conditioning system consists of a
floor-mounted air conditioner / heater unit, ceiling- Heater (Illustration 20A-4, if equipped). The heat-
mounted air conditioner unit, condenser, compres- er is powered by 12 VDC from a 15 amp circuit
sor, heater, defroster, two 15 amp circuit breakers breaker (CB8), employs a two speed switch (S5),
(CB8 and CB9), heater shut-off valve, two and is rated at 40,000 BTUs.
engine-mounted shut-off valves, controls and Drier. The drier stores a volume of refrigerant.
hoses that connect the heater and defroster to the Additionally, it filters and removes moisture from
cooling system of the engine. the refrigerant. The drier receives a warm, high
Air Conditioner / Heater Unit. The floor- pressure liquid (from the condenser) and sends a
mounted air conditioner / heater unit is capable of warm, high pressure liquid (to the expansion
delivering 26,000 BTUs of cooling capacity, valve). The drier is equipped with a binary switch
26,000 BTUs of heating capacity, and is powered which protects the compressor.
by 12 VDC from a 38 amp circuit breaker (CB16). The binary switch is normally closed when the
The air conditioner / heater unit is a three speed system pressure is within operating specifications.
unit with a preset thermostat. The air conditioner / The binary switch will open when the system pres-
heater unit has a cool / heat switch that allows the sure exceeds 312 psi. The binary switch will not
operator to select for cooling or heating of the cab. close again until the pressure has dropped below
The air conditioning system is charged with 225 psi. When the pressure drops below 2 psi,
approximately 4.5 lbs. of R134a Freon. the binary switch will open. The binary switch will
not close again until the pressure is above 28 psi.
NOTE: The Clean Air Act, passed in 1992, speci-
The binary switch can be replaced without recov-
fies that anyone who works on vehicle air condi-
ering the refrigerant. The binary switch is located
tioning systems must be certified by an EPA
in the air conditioner unit on the high pressure
approved agency.
side. The fitting that holds the binary switch is
Air Conditioner Unit. The ceiling-mounted air equipped with a check valve, that prevents the
conditioner unit is capable of delivering 18,500 high pressure coolant from exhausting if the
BTUs of cooling capacity and is powered by switch is removed.
12 VDC from a 38 amp circuit breaker (CB27). Evaporator / Heater Coil. The evaporator / heat-
The air conditioner unit is a three speed unit with er coil is located inside the air conditioner / heater
adjustable thermostat. This air conditioner unit is unit. The evaporator and heater coils are inte-
combined with the floor-mounted air conditioner / grated into one unit. The evaporator coil changes
heater in the air conditioning system circuit. the warm, metered pressure liquid refrigerant
Compressor. The compressor is belt driven and (from the expansion valve) into a cold, low pres-
circulates the refrigerant through the air condition- sure gas. The cold, low pressure gas is sent back
ing system when its clutch is engaged. It receives into the expansion valve. The temperature of this
a cool, low pressure gas and pumps a hot, high low pressure gas is what controls the expansion
pressure gas to the condenser. When the thermo- valve. The colder the gas, the closer a ball will
stat signals for cooling, an electrical signal is sent seat and restrict the refrigerant into the evaporator
to the compressor clutch, engaging the clutch and coil.
driving the compressor.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 20A-1
The heater coil is the medium by which heat is Air Conditioner / Heater Unit (Illustration 20A-1).
transferred from the engine coolant to the opera- Perform the following procedures to remove the
tor’s compartment. A heater shut-off valve is filter for cleaning or replacement:
located on the air conditioner / heater unit and
1. Remove the air screen cover from the air con-
when opened, allows the heat transfer to occur.
ditioner / heater unit’s housing.
When operating the air conditioner, close the
heater shut-off valve for maximum cooling 2. Take the filter out and clean with low pressure
efficiency. air. Replace it with a new filter if necessary.
Defroster (Illustration 20A-4, if equipped). The 3. Install the filter in the air conditioner / heater
defroster is powered by 12 VDC from a 15 amp unit’s housing.
circuit breaker (CB9), employs a two speed switch
4. Install the air screen cover.
(S6) and is rated at 22,000 BTUs.
Air Conditioner Unit (Illustration 20A-2). Perform
Circuit Breakers. Refer to Circuit Breakers in
the following procedures to remove the filter for
the Component Troubleshooting in Section 6
cleaning or replacement:
for troubleshooting of circuit breakers.
1. Grasp the sides of the air conditioner filter, pull
Air Conditioner / Heater Maintenance. The
filter down and remove filter.
remote mounted condenser of the air conditioning
system should be cleaned every 3 months to 2. Clean with low pressure air. Replace it with a
remove debris. The condenser can be cleaned new filter if necessary.
with a fin comb, air hose and nozzle, or soap and
3. Install the filter in the air conditioner unit’s
water. The evaporator / heater coils in the air con-
housing.
ditioner / heater unit should be cleaned every
3 months with compressed air. Inspection. In the event of a cooling problem,
perform the following inspection procedures.
Heater Shut-off Valves (Illustration 20A-4). The
heater shut-off valves control the circulation of
heated coolant through the heat system. One

valve is located on the air conditioning / heater S Death or serious injury could result from a
unit while the other two are located on the engine. runaway truck. Park the truck on a hard,
All three shut-off valves must be fully open for level surface, apply the parking brake and
maximum heating. If any of the heater shut-off block the wheels in both directions to
valves are closed, there will be no circulation of prevent movement of the truck.
heated coolant through the system.
S Rotating fan and belts can cause severe
Hoses. Periodically check the hoses and elbows injury. Stay clear of fan and belts when
for chafing or cracking. Replace as conditions engine is running.
require.
1. Check the compressor drive belt tension and
pulley alignment. Tension on the drive belt

Allow the engine to cool should be such that a firm push with the thumb
completely before removing heater hoses from at a point midway between the two pulleys will
engine. Severe burn potential exists. deflect the belt approximately 3/8”. If the
deflection of the belt is more than 3/8”, adjust
Cleaning and / or Changing The Air Condition- the belt tension.
er Filter
2. Check the condenser for debris and clean if
The air conditioner filter should be cleaned every required.
3 months or as conditions warrant. The filter must
3. Check all electrical connections and ensure
be replaced once a year or as conditions warrant.
that the circuit breakers are set.
If the filter is not cleaned regularly, it may become
partially clogged with lint, dirt, grease or other 4. Checking the compressor clutch will require
debris. The filter should be cleaned or changed starting the engine. When 12 VDC is sent
as conditions warrant. from the thermostat through the binary switch
to the compressor, the compressor’s clutch will
20A-2 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
pop towards the compressor pulley (this will be 6. The 12 VDC signal from the thermostat must
heard). The clutch will then begin to rotate pass through a binary switch, which monitors
with the pulley (this will be seen). low pressure and high pressure in order to
engage the clutch of the compressor (refer to
5. Ensure that the evaporator coil, located inside
Drier in this section).
the air conditioner / heater unit (and ceiling-
mounted air conditioner unit), is not iced up. 7. Check the air conditioning hoses and fittings
The thermostat’s capillary should be posi- for leaks. If a leak is detected, the refrigerant
tioned in the center of the evaporator coil fins. must be recovered prior to making repairs.
If the thermostat is functioning properly when
the fins ice up, the thermostat will remove the NOTE: The Clean Air Act, passed in 1992, speci-
12 VDC to the compressor. This will allow the fies that anyone who works on vehicle air condi-
compressor pulley to free-spin and no refriger- tioning systems must be certified by an EPA
ant will be circulated to the evaporator coil. approved agency.
The ambient temperature will then defrost the
evaporator coil fins. 8. For any further repairs, contact a certified air
conditioning repair technician.
HEATER ÂÂÂÂÂÂÂÂÂÂ
ÂÂÂÂÂÂÂÂÂÂ
FILTER
SHUT-OFF VALVE
CONTROL KNOB
AIR SCREEN
COVER
AIR CONDITIONER /
HEATER UNIT
CONTROLS
Illustration 20A-1. Air Conditioner / Heater Unit
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 20A-3
AIR CONDITIONER
CONTROLS
FILTER
Illustration 20A-2. Ceiling-mounted Air Conditioner
20A-4 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
Air Conditioning and Heating System Troubleshooting (Illustrations 20A-3 and 20A-4)
1. Air conditioning 1. Circuit breaker (CB16 - air condi- 1. Reset or replace circuit breaker
unit does not tioner / heater unit or CB27 - air (CB16 or CB27). Refer to Circuit
power up conditioner unit) is tripped or defec- Breakers of the Component Trou-
tive. bleshooting in Section 6.
2. Harness connector is disconnected 2. Connect or tighten harness
or loose. connector.
3. Loose pin in harness connector. 3. Isolate and repair.
4. Broken or shorted wires. 4. Troubleshoot, isolate and repair.
2. Fan blows limited 1. Heater shut-off valve is open. 1. Close heater shut-off valve
or no cold air
2. Compressor clutch is slipping or 2. Tighten drive belt or replace clutch.
defective.
3. Low Freon charge. 3. Have certified technician recharge
air conditioning system.
4. Thermostat is defective. 4. Replace thermostat.
5. Evaporator coil is iced up. 5. Thermostat is defective. Replace
thermostat.
6. The condenser fan is seized or 6. Unseize fan, replace or check wir-
defective. ing to fan motor.
7. The evaporator / heater coils are 7. Clean with compressed air or
dirty or stopped up. remove restriction.
8. Filter is dirty or stopped up. 8. Clean or replace filter.
9. Binary switch in condenser is 9. Isolate and repair.
defective.
10. Circuit breaker(s) is tripped or 10. Isolate and repair.
defective.
11. The heat / air switch of the air con- 11. Place the heat / air switch in the air
ditioner / heater unit is in the heat position.
position.
12. Defective heat / air switch of air 12. Replace heat / air switch.
conditioning unit.
13. Harness connector(s) is discon- 13. Connect or tighten harness
nected or loose. connector(s).
14. Air conditioner compressor is 14. Contact certified technician to
defective. repair or replace.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 20A-5
3. Air conditioning 1. Drainage hoses are restricted. 1. Remove restriction from hoses.
unit is leaking
water in the cab 2. Drainage hoses have shifted 2. Reposition the drainage hoses.
upwards. The drainage hoses should run
downward to prevent water from
standing in the hoses.
3. Drain vent in drainage pan is 3. Remove restriction from drain vent.
restricted.
4. Heater fan not 1. The heater switch (S5) is defective. 1. Replace heater switch (S5).
turning
2. Circuit breaker (CB8) is tripped or 2. Reset or replace circuit breaker
defective. (CB8). Refer to Circuit Breakers
of the Component Troubleshoot-
ing in Section 6.
3. Defective fan motor. 3. Replace fan motor.
4. Broken or shorted wire. 4. Troubleshoot, isolate and repair.
5. Weatherpack connector or the 5. Ensure weatherpack connector or
male / female wire connectors are male / female wire connectors are
loose or unplugged. connected.
5. Heater fan turning, 1. The shut-off valve(s) is closed. 1. Open shut-off valve(s).
but no warm air
2. Heater hoses kinked or restricted. 2. Unkink or remove restriction from
hoses.
3. Defective engine thermostat (stuck 3. Replace engine thermostat.
open).
4. Low coolant. 4. Check and fill radiator.
5. Engine did not rise to operating 5. Allow engine enough time to reach
temperature. operating temperature.
6. Heater operates in 1. Defective heater switch (S5). 1. Replace heater switch (S5).
only one speed
7. Defroster fan not 1. Defective defroster switch (S6). 1. Replace defroster switch (S6).
turning
ing in Section 6.
continued
20A-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

7. Defroster fan not 5. Weatherpack connector or the 5. Ensure weatherpack connector or

turning male / female wire connectors are male / female wire connectors are
(Continued) loose or unplugged. connected.
8. Defroster fan turn- 1. The shut-off valve(s) is closed. 1. Open shut-off valve(s).
ing, but no warm
2. Defroster hoses kinked or 2. Unkink or remove restriction from
air
restricted. hoses.
open).
5. Engine did not rise to operating 5. Allow engine enough time to reach
temperature. operating temperature.
9. Defroster operates 1. Defective defroster switch (S6). 1. Replace defroster switch (S6).
in only one speed
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 20A-7

Hoist Circuit
20A-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 20A-3. Air Conditioning / Heating Circuit
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 20A-9
20A-10 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
20A-2332 SHT. 01
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 20A-11
Hoist Circuit
20A-12 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 20A-4. Heating Circuit
HEATER
SHUT-OFF VALVE
AIR
CONDITIONER /
HEATER UNIT
CUMMINS
SHUT-OFF VALVE QSM11-C330
ENGINE
20A-2332 SHT. 02
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 20A-13
Hoist Circuit
20A-14 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

20H-Heating System
Section 20H
Heating System
SHUT-OFF VALVE
CUMMINS QSM11-C330
ENGINE
20H-0056
Illustration 20H-1. Heating System Circuit

Introduction. The heating system provides a ered by 12 VDC from a 15 amp circuit breaker
comfortable working environment in a cold climate (CB8), employs a two speed switch (S5), and is
and is essential in removing condensation from rated at 40,000 BTUs.
the windshield in which otherwise would impair
Defroster (Illustration 20H-1). The defroster is
vision. Provided the shut-off valves are open, the
powered by 12 VDC from a 15 amp circuit breaker
engine coolant flows through the heater coils,
(CB9), employs a two speed switch (S6) and is
through the defroster(s) and returns back to the
rated at 22,000 BTUs.
engine block.
Circuit Breakers. Refer to Circuit Breakers in
Major Components (Illustration 20H-1). The
the Component Troubleshooting in Section 6
heater system consists of a heater, defroster(s) (if
for troubleshooting of circuit breakers.
equipped), two 15 amp circuit breakers (CB8 and
CB9), diodes, shut-off valves and hoses. Shut-off Valves (Illustration 20H-1). The shutoff
valves control the flow of heated coolant to the
Heater (Illustration 20H-1). The heater is pow-
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 20H-1

heater and defroster circuits. They must be fully
open for maximum operation. If the shut-off
Allow the engine to cool
valves are closed, there will be no flow of heated completely before removing heater hoses from
coolant to circulate in the circuits. engine. Severe burn potential exists.
Hoses. Periodically check the hoses and elbows
for chafing or cracking. Replace as conditions
require.
Heating System Troubleshooting (Illustration 20H-1)
1. Heater fan not 1. The heater switch (S5) is defective. 1. Replace heater switch (S5).
turning
2. Circuit breaker (CB8) is tripped. 2. Reset circuit breaker (CB8).
3. Circuit breaker (CB8) keeps trip- 3. Circuit is shorted. Troubleshoot,
ping. isolate and repair short.
4. Circuit breaker (CB8) is defective. 4. Replace circuit breaker.
6. Open or shorted wire. 6. Troubleshoot, isolate and replace
wire.
2. Heater or defroster 1. One of the shut-off valves is 1. Open shut-off valve.

fan is turning, but closed.
no warm air is
2. Heater hoses kinked or restricted. 2. Unkink or remove restriction from
present
hoses.
open).
5. Engine is not at operating tempera- 5. Allow engine enough time to reach
ture. operating temperature.
3. Heater operates in 1. Defective heater switch (S5). 1. Replace heater switch (S5).
only one speed
2. Defective wire between heater 2. Troubleshoot, isolate and repair.
switch (S5) and motor.
20H-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

4. Defroster fan not 1. Defective defroster switch (S6). 1. Replace defroster switch (S6).
turning
2. Circuit breaker (CB9) is tripped. 2. Reset circuit breaker (CB9).
3. Circuit breaker (CB9) keeps trip- 3. Circuit is shorted. Troubleshoot,
ping. isolate and repair short.
4. Circuit breaker (CB9) is defective. 4. Replace circuit breaker.
6. Open or shorted wire. 6. Troubleshoot, isolate and replace
wire.
5. Defroster operates 1. Defective defroster switch (S6). 1. Replace defroster switch (S6).
in only one speed
2. Defective wire between defroster 2. Troubleshoot, isolate and repair.
switch (S6) and motor.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 20H-3

Hoist Circuit
20H-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Section 22
Hydraulic System
Introduction. The hydraulic system controls the able for the main hydraulic circuit.
lift, tilt, steering and spreader functions of the Hydraulic Joystick Controls (Illustration 29-2).
truck. The following functions are accomplished by
Major Components (Illustration 22-1). Major depressing the enable switch and maneuvering
components of the hydraulic system include a the joystick:
hydraulic tank, main pump (main / steering), steer 1. Tilt Back. Shift the joystick to the left to tilt the
sensing valve, joystick, lift / tilt valve, lift soft land- mast towards the operator.
ing solenoid valve, auxiliary (spreader / brake)
pump, brake manifold valve, controller enable 2. Tilt Out. Shift the joystick towards the right to
solenoid valve, joystick controller valves, various tilt the mast away from the operator.
actuating cylinders and an accumulator. 3. Lower. Shift the joystick forward to lower the
Hydraulic Tank (Illustration 22-10). The hydraulic attachment. The lower operation is sus-
tank has a 160 gallon capacity. The tank is pended once the amber light is obtained by a
equipped with suction strainers and full-flow return lift soft landing solenoid valve (LSL) which,
line filters. All air entering the tank is filtered when energized, will dump the pilot pressure
through two 10 micron disposable breathers. at port A of the lift valve to the hydraulic tank.
Main Pump (Illustration 22-15). The main pump 4. Lift. Shift the joystick rearward to lift the
is a tandem gear pump that provides hydraulic attachment.
fluid flow to operate the hydraulic circuit. When Controller Enable. The controller enable function
the pump is turned, it creates a vacuum at the is controlled by the seat belt, and the red and
pump inlet which allows atmospheric pressure to green container lights. Unless the seat belt is
force oil through a suction strainer in the tank into buckled and either the red or green container light
the inlet line of the pump. The pump then is illuminated, there will be no pilot pressure for
mechanically pushes this fluid to its outlet port for the lift, lower, tilt-in, and tilt-out functions of the
use in the hydraulic circuit. joystick.
The main pump has two sections, each containing Controller Enable Solenoid Valve (Illustration
a pumping gear set. Each pumps at a maximum 22-15). The controller enable solenoid valve is
rate of 62 gpm at 2100 governed rpm. One of the 3-way solenoid valve located behind the cover
gear sets is dedicated to the steering circuit. It plate on the back of the cab. In a de-energized
supplies fluid to the steer sensing valve and addi- state (seat belt not buckled, or either the red or
tionally supplies the lift / tilt valve. When steering, green container light is not illuminated), hydraulic
the gear set will supply only the amount of fluid pilot pressure will enter port 3 and be dead-
required to steer. The excess flow, not being headed. At the same time, port 1 and port 2 will
used, will supply the lift and tilt valves. This gear be connected, venting the hydraulic pilot pressure
set is the sole source of hydraulic fluid for the tilt of the joystick back to the hydraulic tank. In an
section. The other gear set supplies hydraulic energized state (seat belt buckled and either the
fluid to the lift valve only. The pressure of the red or green container light is illuminated), hydrau-
steering / tilt gear set can be checked at pressure lic pilot pressure will enter port 3 and exit port 1 to
check (PC1). The pressure of the second gear the joystick controller.
set, dedicated to the lift section, can be checked
at pressure check (PC2 or PC1). Lift / Tilt Valve (Illustration 22-15). The lift / tilt
valve, located on the left side in front of the brake
Steer Sensing Valve (Illustration 22-15). The manifold valve, directs the flow of fluid to the lift
steer sensing valve is mounted on the left side in and tilt circuits. It consists of an inlet, tilt, mid inlet,
front of the transmission. It contains a steering lift and outlet sections (Illustration 22-12).
relief valve set at 2500 psi. When the steering
valve (i.e. steering wheel) is turned, the steer The inlet section of the lift / tilt valve receives a
sensing valve directs fluid to the steering valve. maximum of 62 gpm at 2100 rpm from one of the
Any flow not used by the steering circuit is sent to gear sets of the main pump. The main relief,
the lift / tilt valves. When the steering wheel is not located in the inlet, is set at 2900 psi.
being turned, all of the steering pump flow, except The tilt section contains an A port (tilt out) and a B
for a small amount in the load sense line, is avail- port (tilt back). It is connected to the tilt cylinders
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22-1

JOYSTICK
CONTROLLER VALVES
(Illustration 22-14)
CAB TILT
CYLINDER CAB TILT FLOW
(Illustration 22D-2) CONTROL VALVE
(IF EQUIPPED)
(Illustration 22D-2)
LIFT CYLINDER
(Illustration 22-14) STEERING VALVE CONTROLLER
(Illustration 16-2) ENABLE
SOLENOID VALVE
TILT CYLINDER (Illustration 22-14)
CAB TILT
SOLENOID VALVE
(IF EQUIPPED)
(Illustration 22D-1)
MAIN PUMP
AUXILIARY
(SPREADER / BRAKE)
PUMP
SPREADER
RELIEF VALVE
HYDRAULIC TANK
STEER SENSING VALVE

(Illustration 16-1)
LIFT / TILT VALVE
(Illustration 22-12) ACCUMULATOR
LIFT SOFT
LANDING
SOLENOID VALVE
Illustration 22-1. Hydraulic System Components Identification
22-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

by hydraulic hoses. The A port contains a port 2 of the lift soft landing valve. The pilot pressure
relief (located behind the end cap) to limit maxi- to the A port (lower) of the lift valve will be vented
mum tilt out pressure to 2500 psi. When the tilt to the hydraulic tank, disabling lowering capabili-
function of the joystick is operated, pilot pressure ties. In a de-energized state (amber container
is applied to the A or B port endcap to shift the light is not illuminated), hydraulic pilot pressure
main spool of the valve. This directs hydraulic from the B1 port of the joystick will enter the lift
fluid flow to and from the tilt cylinders to tilt the soft landing valve at port 2 and exit port 1. From
mast. The tilt pressure can be checked by instal- here, the hydraulic pilot pressure will be applied to
ling an appropriate gauge on pressure check the A port end cap of the lift section, shifting the
(PC1) and fully retracting and dead-heading the main spool, lowering the inner mast.
tilt cylinders. The tilt out pressure can be checked
Auxiliary (Spreader / Brake) Pump (Illustration
at pressure check (PC1) by placing the attach-
22-15). The auxiliary (spreader / brake) pump,
ment at its lowest position and fully extending and
located on the back side of the transmission, is a
dead-heading the tilt cylinders. Tilt lock valves
tandem gear pump that provides hydraulic fluid
connected to the rod end of the tilt cylinders limit
flow to operate the attachment hydraulic circuit
outward tilt speed to prevent the load from falling
and brake cooling circuit.
out. The hydraulic fluid is restricted in one direc-
tion and free flows in the other. The auxiliary pump has two sections, each con-
taining a pumping gear set. One gear set, pump-
The mid inlet section of the lift / tilt valve receives
ing at a maximum rate of 24 gpm at 2100 rpm, is
62 gpm at 2100 rpm from the other gear set of the
dedicated to the attachment hydraulic circuit. This
main pump. If the tilt function is not being used,
gear set is the sole source of hydraulic fluid for the
the other gear set’s fluid supply will be combined
main attachment valve. The other gear set,
at the mid-inlet section, generating 124 gpm at
pumping at a maximum rate of 9 gpm at 2100
2100 rpm to the lift section. The mid-inlet section
rpm, supplies hydraulic fluid to the brake manifold
contains a pressure relief valve, located in port A,
valve. The pressure of the main attachment gear
that is set at 2900 psi.
set can be checked at pressure check (SHC1).
The lift section contains an A port (lower) and a B The pressure of the brake cooling gear set can be
port (hoist). It is connected through hydraulic checked at pressure check (BCA) on the brake
hoses to the lift cylinders on the mast. When the manifold valve at port A (see Illustration 15C-1).
lift control is operated, pump flow is diverted
Brake Manifold Valve (Illustration 15C-1). The
through this section into the piston end of the lift
brake manifold valve, located on the left side of
cylinders, causing the lift cylinders to extend.
the truck’s chassis, develops pilot pressure, pro-
Maximum pressure is limited by the main relief
tects the hydraulic controls and protects the oil
valve as well as the mid-inlet relief valve. When
cooler. It contains a 400 psi pressure reducer (in
lowering, the operation is reversed and fluid is
port 1) that ensures that the pilot pressure does
directed out of the lift cylinders back into the tank
not exceed 400 psi. The brake manifold valve
passage of the valve. It combines with pump flow
also contains a 250 psi pressure relief (in port 3),
and is directed through the return hose on the out-
ensuring minimum pilot pressure of, at least, 250
let of the valve and back to tank.
psi. It contains a 10 psi, normally closed, pres-
The outlet section provides the connection from sure switch (S23, Illustration 15C-1) in port B and
the return hose back to the hydraulic tank. When a relief valve (in port 2) set for 325 psi. Should
no hydraulic functions are operated, the pump back pressure in the oil cooler circuit exceed 325
output flows from the inlet down the center of the psi, the relief valve will open and relieve pressure
valve to the outlet and returns through the return to the hydraulic tank. The brake manifold valve
filter that is mounted in the tank. also contains a 15 psi check in port 4; its function
is to ensure that anytime flow is present that the
Lift Soft Landing Solenoid Valve (Illustration
10 psi, required to open pressure switch (S23),
22-15). The lift soft landing solenoid valve is a
can be obtained. Should the oil pressure drop
3-way solenoid valve located on the A port end
below 10 psi, pressure switch (S23) will close,
cap of the lift section. When the amber container
sending ground to the Brake Fail light (DS8), illu-
light is illuminated, the solenoid is energized. In
minating the light.
an energized state, hydraulic pilot pressure from
the B1 port of the joystick is dead-headed at port
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22-3

Joystick Controller Valves (Illustration 22-15). light illuminated when approaching the container.
The joystick controller valves, located beneath the The red light operates as follows: 12 VDC is pres-
joystick, when activated, will direct the pilot fluid to ent at both the white and red wires of proximity
the corresponding side of the lift / tilt valve to shift switch (S45). 12 VDC is present on the red wire
the selected main spool (lift or tilt). They control of proximity switch (S37). The 12 VDC present on
the amount of pilot pressure delivered to the lift / the red wire is used for proximity switch coil opera-
tilt valve end caps. By metering the fluid, greater tion only. As each of the proximity switches is tar-
control over the load is obtained. geted, they close the internal contacts of the white
and orange wires respectively. When S45 senses
Lift Cylinders (Illustration 22-15). The lift cylin- its target, 12 VDC is sent from the white wire #200
ders operate on the principle of power up and to the orange wire #234 to the terminal strip in the
gravity down. There are flow control regulators, right end beam electrical box. Wire #234 is jump-
located on the piston end of these cylinders, that ered to wire #235 at this terminal strip. 12 VDC
restrict the flow of fluid exiting the cylinders, allow- on wire #235 is sent to the white wire #235 of
ing greater control of the load when lowering. The proximity switch (S37). When S37 senses its tar-
regulators variably restrict the flow of fluid, accord- get, the internal contacts close and the 12 VDC on
ing to the weight of the load, in one direction only. the white wire #235 is sent out orange wire #236
The regulators allow free-flow in the other direc- to the terminal strip in the left end beam electrical
tion for lifting. The rod end of the lift cylinders are box. Wire #236 is jumpered to wire #237 at this
vented back to an air space in the top of the terminal strip. 12 VDC on the wire #237 is sent to
hydraulic tank. terminal #1 of diode bank (DB5). 12 VDC will
Accumulator (Illustration 22-15). The accumula- pass from terminal #1 to terminal #2 of DB5 to the
tor acts as a shock absorber in the hydraulic sys- Red container light, illuminating the light. Addi-
tem. When the driven member of the hydraulic tionally, 12 VDC on terminal #1 of DB5 is jump-
system stops suddenly, it creates a pressure wave ered to terminal #5 of DB3. 12 VDC will pass from
that travels back through the system. This shock terminal #5 to terminal #6 of DB3 down wire #289
wave can develop peak pressures several times to the controller enable relay (K20, see Relay K20
greater than normal working pressures and can be Operation). Additionally, the 12 VDC on wire
the source of system failure. The gas cushion in #237 will provide operating power to the 40-ft.
an accumulator will minimize this shock, protecting expand switch (S32) and the 20-ft. retract switch
expensive hydraulic components. (S33). 12 VDC on wire #237 also energizes the
work light relay (K19). K19 will energize, connect-
The accumulator is connected to the lift pipe ing pins 5 to 3 and 6 to 4. 12 VDC at pin 5 will
assembly and is a hydro-pneumatic piston type pass out pin 3, down wire #242 to the left work
accumulator which is precharged to 1250 psi of light (DS32), illuminating it. 12 VDC at pin 6 will
dry nitrogen. Refer to Section 22E for procedures pass out pin 4, down wire #242 to the right work
for checking the precharge and charging the accu- light (DS33), illuminating it. Additionally, 12 VDC
mulator. at pin 4 of relay (K19) is sent down wire #263 to
Tilt Cylinders (Illustration 22-15). The tilt cylin- the red container light mounted on the attach-
ders are double-acting. They alternately receive ment, illuminating the light.
pressurized fluid on one side of the piston, while Green Light Operation (Locked). The green
the fluid on the other side returns to tank. There light operates as follows: 12 VDC is present at
are tilt lock valves (preset at 2250 psi) connected both the white and red wires of proximity switch
to the rod end of these cylinders. These valves (S44). 12 VDC is present on the red wire of prox-
regulate the flow of fluid exiting the cylinders, limit- imity switch (S36). The 12 VDC present on the
ing the outward tilt speed to prevent the load from red wires is used for proximity switch coil opera-
falling out. To change tilt cylinder direction, the tion only. As each of the proximity switches is tar-
pressurized and vented sides of the piston are geted, they close the internal contacts of the white
exchanged through the valving. and orange wires respectively. When S44 senses
Lift / Tilt Pilot Pressure Operation its target, 12 VDC is sent from the white wire #200
(Illustration 29-33) to the orange wire #230 to the terminal strip in the
right end beam electrical box. Wire #230 is jump-
Red Light Operation (Unlocked). Under normal ered to wire #231 at this terminal strip. 12 VDC
operation, the red container light will be the only on wire #231 is sent to the white wire #231 of
22-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

proximity switch (S36). When S36 senses its tar- tion of the red or green container light will send
get, the internal contacts close and the 12 VDC on 12 VDC through a bank of three diodes (DB3).
the white wire #231 is sent out orange wire #232 The diodes are used to isolate the red container
to the terminal strip in the left end beam electrical light from the green container light. From here,
box. Wire #232 is jumpered to wire #233 at this the 12 VDC will be placed on wire #289 to pin 86
terminal strip. 12 VDC on the wire #233 is sent to of the controller enable relay (K20), energizing the
terminal #3 of diode bank (DB5). 12 VDC will relay provided the operator presence switch
pass from terminal #3 to terminal #4 of DB5 to the (OPS) is closed. When the operator is in the seat,
Green container light, illuminating the light. Addi- the OPS switch will close and send ground to pin
tionally, 12 VDC on terminal #3 of DB5 is jump- 85 of relay K20. When K20 energizes, 12 VDC
ered to terminal #1 of DB3. 12 VDC will pass from (supplied from CB15 to pin 30) will be sent out pin
terminal #1 to terminal #2 of DB3 down wire #289 87 of K20 down wire #79. This will energize the
to the controller enable relay (K20, see Relay K20 controller enable solenoid valve (CDS) and allow
Operation). 12 VDC on wire #233 also energizes pilot pressure present at port 3 to pass out port 1
the relay (K29). K29 will energize, connecting of this valve, and supply pilot pressure to the joys-
pins 9 and 5. 12 VDC at pin 9 will pass out pin 5, tick for lift / tilt hydraulic functions. When the
down wire #262 to the green container light Green or Red container light is not illuminated,
mounted on the attachment, illuminating the light. 12 VDC will not be supplied to pin 86 of relay K20
and K20 will not energize unless the override
Amber Light Operation (On Container). The
switch is activated. The override switch is a key
amber light operates as follows: 12 VDC is pres-
type switch that must be held in its closed state to
ent at both the white and red wires of proximity
override the interlock operation of the Red, Green,
switch (S46). 12 VDC is present on the red wire
and Amber container lights. 12 VDC is supplied to
only of proximity switches (S49, S38 and S41).
the override switch from CB18 on wire #210 to the
The 12 VDC present on the red wires is used for
B post of the override switch. Activation of the
proximity switch coil operation only. As each of
override switch will send 12 VDC from the B post
the proximity switches is targeted, they close the
out the S post of the override switch and down
internal contacts of the white and orange wires
wire #221 to pin 14 of relay K54, energizing K54.
respectively. When S46 senses its target, 12 VDC
Additionally, 12 VDC on wire #221 is sent to termi-
is sent from the white wire #200 to the orange wire
nal #3 of diode bank DB4. 12 VDC on terminal #3
#238. This voltage is sent to the white wire #238
will pass out terminal #4 of DB4 to the output side
of S49. When S49 senses its target, the internal
of DB3, down wire #289 to the controller enable
contacts close and the 12 VDC on wire #238 is
relay [(K20, pin 86), Illustration 22-15].
sent out the orange wire #239 to S38 on the white
wire #239. When S38 senses its target, 12 VDC Relay K59 Operation (Illustrations 22-15 and
is sent from the white wire #239 to the orange wire 29-28). Relay K59 operates as follows: 12 VDC
#240. This voltage is sent to the white wire #240 is present at pins 14 and 9 of the relay. Relay
of S41. When S41 senses its target, the internal K59 will energize when the operator occupies the
contacts close and the 12 VDC on wire #240 is seat. When the operator occupies the seat, the
sent out wire #241 to pin 14 of the twistlock inter- operator present switch (OPS) will close and pass
lock relay (K14), energizing K14. When K14 ener- ground to pin 13 of relay K59, energizing K59.
gizes, ground at pin 5 is sent out pin 9 to pin 13 of When relay K59 energizes, 12 VDC at pin 9 will
relays (K6 and K7). 12 VDC on wire #241 is sent be sent out pin 5 to the micro-switches of the joys-
to terminal #5 of diode bank (DB5). 12 VDC will tick. When the operator is not in the operator’s
pass from terminal #5 to terminal #6 of DB5 to the seat, both electrical and hydraulic operations of
Amber on-container light, illuminating the light. the joystick are suspended.
12 VDC on wire #241is additionally sent to pin 1
Relay K54 / K58 Operation (Illustration 29-28).
of relay (K54) and to pin 14 of relay (K30). This
Relay K54 is controlled by the override key switch
will energize K30, connecting pins 9 and 5.
only. K54 in conjunction with the on-container
12 VDC at pin 9 is sent out pin 5, down wire #261,
proximity switches (S46, S49, S38, S41) control
illuminating the amber on-container light mounted
the lift soft landing solenoid. K54 operates as fol-
on the attachment.
lows: The coil of relay K54 is controlled by pins
Relay K20 Operation (Illustrations 22-15 and 13 and 14. Ground is connected to pin 13. Wire
29-28). Relay K20 operates as follows: illumina- #221, from the override key switch terminal S, is
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 22-5
connected to pin 14 and jumpered to diode bank
(DB4) at terminal #3. The common pin 9 (wire SETUP PUSH
BUTTON MULTICOLOR
#90) is connected to pin 1 (wire #241) in a de-en-
RED L.E.D.
ergized state and in an energized state, the com-
L.E.D.
mon pin 9 is connected to pin 5 (no wire at-
tached). 12 VDC is supplied to pin 1 (wire #241)
from the activation of all four on-container proximi-
ty switches (S46, S49, S38, S41). When 12 VDC
is present at pin 9 of relay K54, relay K58 will
energize. When relay K58 energizes, 12 VDC at
pin 9 is sent out pin 5 onto wire #90; this will ener-
gize the lift soft landing valve. When the lift soft
landing valve is energized, lowering pilot pressure
(from the joystick, present at port 2 of the lift soft
landing valve) is dead-headed at the lift soft land-
ing valve and is not allowed to stroke the spool of
the lift valve. Pilot pressure, which supplied the
spool of the lift valve, is now vented to the hydrau-
lic tank from port 1 to port 3 of the lift soft landing
valve. The spool of the lift valve (located in the lift Illustration 22-2. Ultrasonic Proximity Sensor
/ tilt valve bank) then spring returns to its neutral
state and lowering capabilities are suspended un- Damage Free System (Optional)
less the override switch has been activated.
The damage free system is designed to help pre-
Override Switch (Illustration 29-29). There is a vent damage to the top of the container by
key type override switch, located on the back of decreasing the lowering speed when the tips of
the control stand, that is used to bypass the inter- the twistlocks are within 18 inches of the top of the
lock circuitry (red, green and amber container container. An Ultrasonic Proximity sensor detects
lights). The override switch operates as follows: the container and sends a electrical control signal
The switch must be held into the on position for to a Slow Down Manifold, that restricts the hydrau-
12 VDC to be present at the B terminal. When lic flow back to the tank.
this switch is activated, 12 VDC will be sent out
terminal S (wire #221) to the coil of relay K54. Ultrasonic Proximity Sensor (Programming)
This will energize K54 and open the circuit of the (Illustration 22-2)
lift soft landing solenoid, de-energizing the lift soft 1. Position the truck and a container on a hard
landing valve. This allows lowering pilot pressure level surface. Place the shifter in the neutral
to reach the spool of the lift valve even when the position and apply the parking brakes.
amber light is illuminated. Wire #221 is jumpered
from the coil of relay K54 to diode bank DB4, ter-
minal #3. With the override switch activated, 12
Death or Serious injury can
VDC will pass from terminal #3 out terminal #4 of occur from falls. Always use OSHA approved
diode bank DB4. Terminal #4 of DB4 is con- ladders, stands or manlifts to reach high
nected to diode bank DB3, terminal #2. The out- places on the truck.
puts of DB3 are all jumped together and con-
nected to wire #289. Wire #289, in conjunction 2. Depress and hold the setup push button. The
with the seat belt switch (S18), control the control- multicolored L.E.D. will rapidly flash amber for
ler enable relay K20 (see Relay K20 Operation). approximately 3 seconds and then flash
green.

The override switch should 3. Release the setup push button, the multicol-
only be used while maintenancing the machine ored L.E.D. will continue to flash green. This
or in an emergency. signifies that the sensor is ready for the first
limit.
22-6 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
4. Lower the attachment until the tips of the twist- the lowering speed of the container will not be
locks are 6 inches from the top of a container. affected.
Depress the setup push button once and
To Set The Lowering Speed
release. The multicolored L.E.D. will flash
amber, indicating the first limit has been set 1. Park the truck on level ground. Place the shift
and that the sensor is ready for the second control in the neutral position and apply the
limit. parking brake.
5. Raise the attachment until the tips of the twist-
locks are approximately 18 inches above the
container. Depress the setup push button occur from being crushed. Do not attempt to
once and release. The multicolored L.E.D. adjust the slow down manifold from ground
turns the color that indicates where the object level in front of the truck. Always adjust the
is located. The sensor has no time out for set- slow down manifold from the access plate
ting the limits. provided on the deck of the chassis.
Multicolor L.E.D. Color Indications
2. Remove the access plate from the deck of the
OFF – Object is not being detected. chassis for access to the slow down manifold.
Red – Object detected outside the window 3. Loosen the jam nut and turn the set screw
limits. clockwise to reduce the lowering speed. Turn
Green – Object detected inside the window limits. the set screw counterclockwise to increase the
lowering speed.
The red L.E.D. indicates the output states. If the
L.E.D. is on the outputs are active (on). If the 4. When the desired lowering speed has been
L.E.D. is off, the outputs are non active (OFF). achieved, tighten the jam nut and re-install the
access plate.
Slow Down Manifold (Illustrations 22-3, 22-4,
22-15, and 29-60). The slow down manifold is
controlled by the Ultrasonic Sensor through relays
(K55 and K56). When the slow down manifold is FLOW CONTROL
energized, the hydraulic flow exiting the lift cylin- ADJUSTMENT
ders is restricted and lowering speed is reduced. SOLENOID
The lowering speed can be adjusted by the Flow
Control Adjustment Set screw located on top of
the Manifold. The Slow Down Manifold is located
inside the chassis above the drive axle. Electrical
operation is as follows: When the attachment is
18 inches above the container, the ultrasonic
proximity sensor (UPR3) will energize, placing
12 VDC on wire #284. Wire #284 is connected to
the common pin 9 of relay K55. In a de-energized
state, 12 VDC at pin 9 will pass out pin 1, down
wire #288 to pin 14 of relay K56. This will ener-
gize K56. 12 VDC at the common pin 9 will be
sent out pin 5, down wire #285 and will energize
the solenoid of the slow down valve (DFV). This
will shift an internal spool and restrict the hydraulic SLOW DOWN
flow exiting the lift cylinders to the hydraulic tank. MANIFOLD
Additionally, 12 VDC at pin 5 of relay K56 is sent
down wire #285A to a clear slow down light, illumi-
nating the light. K55 is energized by illumination Illustration 22-3. Slow Down Manifold
of the Green container light. If K55 is energized,
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 22-7
22-6).
NOTE: The only way to stop the lowering of the
load is by closing the manual lowering valve.
4. After the load has been fully lowered, close
the manual lowering valve (refer to Closing
The Manual Lowering Valve).
STEM
SCREW
COLLAR
TO TO / FROM TO / FROM
HYDRAULIC LIFT LIFT
TANK VALVE CYLINDERS LOCK
PLATE
Illustration 22-4. Slow Down Manifold
Manual Lowering Valve Operation VALVE

STEM
The manual lowering valve should only be opened
when normal lowering methods cannot be per-
formed.

S Death or serious injury could result from
being crushed. Do not allow anyone near
the container handling truck - certainly not
walking, standing under, or beside the load
or lifting mechanism.
S Death or serious injury could result from a
runaway truck. Apply the parking brake,
block the wheels in both directions to Illustration 22-5. Manual Lowering Valve
prevent movement of the truck and Lock Out
& Tag Out the truck. Closing The Manual Lowering Valve (Illustration
22-5). The manual lowering valve must be closed
Opening The Manual Lowering Valve (Illustration and locked before operating the container han-
22-5). Perform the following procedures to open dling truck. Perform the following procedures to
the manual lowering valve: close the manual lowering valve:
1. Remove the stem screw and collar. 1. Turn the valve stem clockwise 1/4 turn until the
2. Remove the lock plate. notches, located on top of the valve stem,
point toward the sides of the valve block (note
3. Turn the valve stem counterclockwise 1/4 turn position of valve stem in Illustration 22-7).
until the notches on top of the valve stem align
with the hydraulic fittings of the valve block 2. Install the lock plate over the valve stem.
(note position of valve stem in Illustration Ensure that the notch of the lock plate is secu-
red by the stud on the valve block (see Illustra-
22-8 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
tion 22-5). Servicing The Hydraulic System
3. Install collar over valve stem. Hydraulic Operation. All hydraulic functions
should be checked daily for free operation (see
4. Install stem screw and tighten.
the Daily Checks section in the Operator’s
Guide).
Checking The Fluid Level (Illustration 22-10).
The hydraulic fluid level can be checked at the
sight glasses located on the side of the hydraulic
FULLY tank. The hydraulic fluid level must be maintained
OPEN
between the upper (Full) and lower (Low) sight
glasses. This check must be performed daily.
Before adding hydraulic fluid to the tank, ensure
that the lift cylinders are fully retracted and refer to
the Fuel and Lubricant Specifications in the
1/4 turn Appendices for the type of fluid to be used.
Remove the filler cap with dipstick (8) and check
the condition of the strainer (9) before adding
hydraulic fluid. Add hydraulic fluid until the fluid
Illustration 22-6. Opening The Lowering Valve level is even with the FULL mark on the dipstick.
When the dipstick and filler cap are reinstalled, be
sure the cap is tightened securely. The filler cap
is a pressure type cap that requires 4 PSI internal
pressure to unseat the cap.
Not adhering to the above pro-

cedure can lead to overfilling of the hydraulic
tank. As a result, hydraulic fluid will come out
the breathers.
1/4 turn
NOTE: The filler neck has a link that can be
raised into position above the filler cap and pad-
locked, preventing unauthorized access to the
FULLY CLOSED hydraulic tank.
Illustration 22-7. Closing The Lowering Valve Breather Filters (Illustration 22-10). Replace the
breather filters (3) after the first 50 hours of opera-
tion and thereafter yearly or 3000 hours, whichev-
er comes first. More frequent replacement may
be necessary if the machine is being operated
under extremely dusty conditions.
Return Hydraulic Filters (Illustration 22-10). The
return hydraulic filters are made up of 10 micron
corrugated paper and are non-reusable. These
filters should be changed after the first 50 hours of
operation and every 6 months or 1500 hours,
whichever comes first, thereafter. Perform the fol-
lowing procedures to service the return hydraulic
STUD filters:
Illustration 22-8. Lock Plate Position

Used return hydraulic filters
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 22-9
should be disposed of according to federal 6. Remove the suction access cover (14) and
and local regulations. gasket (15).
1. Remove the two nuts (10) and lockwashers 7. Remove the suction strainers (2) from the
(11). hydraulic tank and clean in solvent. Dry with
compressed air.
2. Lift the filter head assembly off the studs of the
return filter assembly (7) to gain access to the 8. Steam clean the interior of the hydraulic tank
filter. (6).
3. Remove the filter.

Do Not clean the interior of
4. Inspect the O-ring for serviceable condition
the hydraulic reservoir with a flammable
and replace if necessary.
solvent; this can create a serious fire hazard.
5. Install the return filter assembly (7) by revers-
ing the removal procedures. Torque nuts to 9. Install new return filters (7).
10-12 ft-lbs. 10. Re-install suction strainers (2).
Suction Strainers (Illustration 22-10). The suc- 11. Re-install suction access cover (14) and
tion strainers (2) should be cleaned yearly or gasket (15).
every 3000 hours, whichever comes first.
12. Re-install the drain plug (1).
Changing The Hydraulic Fluid (Illustration
22-10). The hydraulic fluid should be changed 13. Install new breather filters (3).
yearly or every 3000 hours, whichever comes first. 14. Clean and re-install strainer (9).
The hydraulic fluid must be also be changed in the
event of a catastrophic failure of a hydraulic com- 15. Fill tank with approximately 5 gallons of
ponent. Refer to the Fuel and Lubricant Specifi- hydraulic fluid. Inspect suction access cover
cations chart in the Appendices for the proper and gasket for leaks. If there are no leaks
type of fluid to be used and perform the following detected, fill the hydraulic tank to the FULL
procedures to change the hydraulic fluid. mark on the dipstick. If a leak is detected,
repair before adding hydraulic fluid.
16. Inspect hydraulic tank fittings and hoses for
leaks. Tighten connections / bolts as required.
S Dispose of drained hydraulic fluid in accor-
dance with federal and local regulations.
S The lift cylinder should be fully retracted to
keep dilution of the new hydraulic fluid to a
minimum.
S Plug all hoses when they are disconnected
to prevent foreign matter from entering the
hydraulic system.
1. Park on level ground, block the wheels and
Lock-Out and Tag-Out truck.
2. Provide a suitable container and remove the
drain plug (1) and drain the hydraulic fluid.
The drain plug must be removed to completely
drain the hydraulic tank.
3. Remove the filler cap with dipstick (8) and
strainer (9).
4. Remove the breather filters (3).
5. Remove the return filters (7). Illustration 22-9. Detecting Hydraulic Leaks
22-10 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
10
11
1. DRAIN PLUG 7
2. SUCTION STRAINER 3
3. BREATHER FILTER 6
4. O-RING
8 4
5. ADAPTER
6. HYDRAULIC TANK 5
7. RETURN FILTER ASSEMBLY
8. FILLER CAP w/DIPSTICK
9. STRAINER
10. NUT
11. LOCKWASHER 9
12. SIGHT GLASS
13. BOLT w/WASHER
14. SUCTION ACCESS COVER
15. GASKET
2
12
1
15
14
13
Illustration 22-10. Hydraulic Tank Components Identification
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22-11

Hydraulic Hose Assemblies and Fittings. All should a relief be blown loose, hot, pressur-
hydraulic hose assemblies should be checked ized fluid will be forced from the open port.
daily for chafed or cracked hoses. Check daily to This could cause severe bodily injury.
ensure that there are no loose fittings on the
hydraulic connections. Lift / Tilt Valve (Illustration 22-12)
The lift / tilt valve contains the main inlet relief
valve in the inlet section, a port relief valve in port

Do Not use hands to check
A of the tilt section (for tilt out only) and a relief
for hydraulic leaks. Because the hydraulic
valve in the A port of the mid-inlet section.
system is under high pressure, leaks could
develop that can not be seen, but will pene- Main Relief Valve (located in the inlet section)
trate the skin and possibly cause other serious
1. Install an appropriate pressure gauge into
injuries. When checking for hydraulic leaks,
pressure check (PC1, Illustration 22-11).
wear heavy gloves and safety goggles, and
use a piece of cardboard or wood to find leaks. 2. Tilt the mast all the way back and dead-head
(See Illustration 22-9). the tilt cylinders making certain the cylinders
are fully retracted, otherwise the gauge will
never read the correct pressure.
AUXILIARY
3. At high idle, observe gauge and set pressure
(SPREADER / BRAKE)
PUMP
for 2900 psi. Refer to procedures 4. through
PRESSURE 6. to set the pressure.
CHECK (PC2)
4. Remove the cover cap and loosen the locknut
PRESSURE on the main relief valve (see Illustration
CHECK (PC1) MAIN 22-12).
PUMP 5. Turn the setscrew clockwise to increase the
pressure or counterclockwise to decrease the
pressure.
6. Tighten the locknut after the pressure has
been set and re-install the cover cap.
Tilt Port Relief Valve (located in the A port of the
tilt section). The tilt port relief valve limits the tilt
out pressure only.
Illustration 22-11. Hydraulic Pressure Checks
2. Tilt the mast fully forward and dead-head the
Setting Hydraulic Pressures tilt cylinders making certain the cylinders are
fully extended, otherwise the gauge will never
Hydraulic pressures must be set at recommended read 2500 psi.
engine speed. The hydraulic fluid should be at
operating temperature before adjusting hydraulic 3. At high idle, observe gauge and set pressure
pressures. for 2500 psi as required. Refer to procedures
4. through 6. to set the pressure.
4. Loosen the locknut on the tilt relief valve (see

Illustration 22-12).
S Under no circumstances, when setting pres-
sures, allow any portion of your body to be 5. Turn the setscrew clockwise to increase the
positioned in front of the relief. It is possible pressure or counterclockwise to decrease the
that the relief could be blown loose with pressure.
great force which could cause severe bodily 6. Tighten the locknut after the pressure has
injury or death. been set.
S Fluid passing over a relief generates heat;
22-12 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
TILT SECTION
INLET SECTION LIFT SECTION
MAIN RELIEF VALVE

(SET TO 2900 PSI
AT HIGH IDLE)
TILT PORT RELIEF

(LOCATED BEHIND
THE END CAP)
(SET TO 2500 PSI
AT HIGH IDLE)
MID INLET
SECTION
OUTLET SECTION
PRESSURE
RELIEF VALVE
(SET TO 2900 PSI
AT HIGH IDLE)
Illustration 22-12. Lift / Tilt Valve

Mid-inlet Pressure Relief Valve (located in the A 5. Install an appropriate pressure gauge in pres-
port of the mid-inlet section) sure check (PC2, Illustration 22-11).
1. Install an appropriate pressure gauge into 6. Fully extend and dead-head the lift cylinders.
7. At high idle, observe gauge and set the mid-in-
2. Tilt the mast all the way back and dead-head let pressure relief valve for 2900 psi. Refer to
the tilt cylinders making certain the cylinders procedures 9. through 11. to set the pressure.
are fully retracted, otherwise the gauge will
8. Loosen the locknut on the mid-inlet pressure
never read the correct pressure.
relief valve (see Illustration 22-12).
3. Remove the cover cap and loosen the locknut
9. Turn the setscrew clockwise to increase the
on the main relief valve of the inlet section
(see Illustration 22-12).
pressure.
pressure to 3000 psi.
been set.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 22-13
11. Re-install pressure gauge in pressure check pressure check (Illustration 22-9).
(PC1) and perform the pressure setting proce-
2. Fully extend and dead-head the tilt cylinders.
dures to set the main relief valve (located in
the inlet section) back to 2900 psi. 3. Observe the pressure gauge (gauge should
indicate 2250 psi at low idle). If unable to
Steer Sensing Valve (Illustration 16-1). The
obtain this pressure reading, perform proce-
pressure relief is located in the bottom of the steer
dures 4. through 8.
sensing valve.
4. Remove the cap from the pressure relief valve.
1. Install 3000 psi pressure gauge into pressure
check (PC1, Illustration 22-11). 5. Loosen the locknut on the pressure relief
valve.
2. Steer truck all the way to either side and dead-
head the steer cylinder. 6. Fully extend and dead-head the tilt cylinders.
3. At high idle, observe gauge and set pressure 7. Turn the setscrew clockwise to increase the
for 2500 psi if required. Refer to procedures pressure or counterclockwise to decrease the
4. through 6. to set the pressure. pressure. Adjust the setscrew until the pres-
sure gauge indicates 2250 psi.
4. Remove the nut on the top of the steer sens-
ing valve at the PP port. The adjustment 8. Tighten the locknut and re-install the cap after
screw is located inside this port. the pressure has been set.
5. Turn the setscrew clockwise to increase the Brake Manifold Valve (Illustration 15C-1)
The brake manifold valve contains a 250 psi pres-
pressure.
sure relief in port 3, a 325 psi pressure relief in
6. Re-install the nut in the PP port after the pres- port 2 and a 400 psi pressure reducer in port 1.
sure has been set.
250 psi Pressure Relief
pressure check (BCA, located on port A of the
brake manifold valve, Illustration 22-15).
2. At low idle, observe gauge and set pressure
for 250 psi if required. Refer to procedures 3.
through 5. to set the pressure.
3. Remove the end cap and loosen the locknut
on the 250 psi relief.
pressure or counter-clockwise to decrease the
pressure.
5. Tighten the locknut and re-install the end cap
PRESSURE
after the pressure has been set.
RELIEF VALVE
CAP 325 psi Pressure Relief. This relief has been pre-
PRESSURE CHECK set at the factory. If adjustment of it is required,
remove the wire tie from the end cap.
Illustration 22-13. Tilt Lock Valve
NOTE: The 250 psi pressure relief must be set
prior to procedure 1.
Tilt Lock Valve (Illustration 22-13). The pressure
relief valve of the tilt lock valve is located on the 1. Install an appropriate pressure gauge into
bottom of the tilt lock valve, facing the piston end pressure check (BCA, located on port A of the
of the tilt cylinder. Perform the following proce- brake manifold valve, Illustration 22-15).
dures to set the pressure.
2. Remove the hydraulic hose from port C of the
1. Install an appropriate pressure gauge into the
22-14 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
7/05)
brake manifold valve. Cap the hose and plug strainers. Refer to Changing The Hydraulic
the port. Fluid in the front of this section. Visually inspect
and clean strainers with solvent. Clogged suction
strainers may lead to any of the following:
for 500 psi if required (the gauge reading at
pressure check (BCA) will be the sum of both 1. Pump cavitation.
the 250 psi relief and the 325 psi relief). Refer
2. Reduced flow rate.
to procedures 4. through 7. to set the pres-
sure. 3. Increased response time of the hydraulic
system.
4. Remove the end cap and loosen the locknut
on the 325 psi relief. 4. Premature pump failure.
5. Turn the setscrew clockwise to increase the Main Pump. Troubleshoot the main pump by
pressure or counter-clockwise to decrease the using a flowmeter on the output side of the pump
pressure. to determine if the pump is producing the correct
flow. At high idle (2100 rpm), pump output flow
should be approximately 62 gpm per gear set. At
after the pressure has been set.
low idle (750 rpm), pump output flow should be
7. Reconnect the hydraulic hose to port C of the approximately 19 gpm (per gear set). It is pos-
brake manifold valve. sible, due to pump slippage which will increase
with wear, that the pump may produce enough
400 psi Pressure Reducer. This reducer has
flow at high idle and not produce enough flow at
been preset at the factory. If adjustment of it is
low idle. Therefore, it is critical that the flow rate
required, remove the wire tie from the end cap.
at high idle and low idle be checked. The pump
1. Install an appropriate pressure gauge into must produce the required flow rate at the
pressure check (RCD, located on port D of the required pressure setting.
brake manifold valve, Illustration 22-15).
Should flow rate be low, troubleshoot as follows:
1. Low hydraulic fluid.
for 400 psi if required. Refer to procedures 3.
through 5. to set the pressure. 2. Improper hydraulic fluid.
3. Remove the end cap and loosen the locknut 3. Suction hose not clamped properly.
on the 400 psi reducer.
4. Suction line is restricted or crimped.
5. Hydraulic strainers, located in the bottom of
pressure or counter-clockwise to decrease the
the tank, are clogged.
pressure.
6. Defective pump.
after the pressure has been set. Auxiliary (Spreader / Brake) Pump. Trouble-
shoot the auxiliary pump by using a flowmeter on
Troubleshooting The Major Components
the output side of the pump to determine if the
pump is producing the correct flow. At high idle
This section contains information that will assist in (2100 rpm), pump output flow should be approxi-
determining the operational status of the major mately 24 gpm for the attachment gear set and 9
components. gpm for the brake cooler gear set. At low idle
(750 rpm), pump output flow should be approxi-
Hydraulic Tank. Visually inspect for leaks on the
mately 7 gpm for the attachment gear set and 2.5
hydraulic tank at the fittings, breathers, welds and
gpm for the brake cooler gear set. It is possible,
connecting hoses. Ensure that the hydraulic tank
due to pump slippage which will increase with
has the proper fluid level. In time or after cata-
wear, that the pump may produce enough flow at
strophic failure of a hydraulic component the suc-
high idle and not produce enough flow at low idle.
tion strainers, located in the bottom of the tank,
Therefore, it is critical that the flow rate at high idle
can become clogged. The most efficient way to
and low idle be checked. The pump must pro-
determine that this condition has occurred is to
duce the required flow rate at the required pres-
drain the hydraulic tank and remove the suction
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 7/05)

06/03) 22-15
sure setting. the piston packing. Repack the cylinder.
Should flow rate be low, troubleshoot as follows: e. If fluid flow is minimum (not sustained
flow), reconnect the hose and continue to
1. Low hydraulic fluid.
troubleshoot the steering circuit.
2. Improper hydraulic fluid.
4. Install a flowmeter in the main hydraulic line at
3. Suction hose not clamped properly. the steer sensing valve and check the flow
rate. In a non-steering state, approximately 62
4. Suction line is restricted or crimped.
gpm at 2100 rpm will be read. While steering,
5. Hydraulic strainers, located in the bottom of the flow rate should decrease. This proves
the tank, are clogged. that the spool in the load sense valve has
shifted to the steering circuit. Fully tilt back
6. Defective pump.
and dead-head the tilt cylinders. Ensure that
Steer Sensing Valve. In a non-steering state, you have 62 gpm at 2100 rpm at 2900 psi.
hydraulic fluid flow will enter the steer sensing
5. If flow rates are correct, adjust the pressure
valve at the P (pressure) port and will exit the
setting of the steer sensing valve (refer to the
steer sensing valve at the EF (excess flow) port
Setting Hydraulic Pressures procedures for
with the exception of a small amount that is sent
setting the hydraulic pressure for the steer
out the LS (load sense) port, used to charge the
sensing valve). If unable to obtain the correct
steering valve. In a steering state, hydraulic fluid
pressure setting:
flow will enter the steer sensing valve at the P
port. Pressure in the load sense line will increase, a. Defective steer sense relief.
diverting a percentage of the main flow, from the P
b. Defective steer sensing valve.
port, out the CF (control flow) port, through the
steer sensing valve to the steer cylinder. The per- c. Defective steering valve.
centage of this fluid to the CF port can vary great-
Lift / Tilt Valve. Perform the following procedures
ly depending on how fast and how long the steer-
to troubleshoot (refer to the Setting Hydraulic
ing valve is turned. The remaining percentage of
Pressures procedures of the Lift / Tilt Valve if the
unused fluid flow not used in the steering circuit
required pressure readings are incorrect):
will be sent out the EF port to the lift / tilt valve.
Troubleshoot the steer sensing valve for proper 1. Inlet Section
operation. Perform the following procedures to
a. Install appropriate pressure gauge into
troubleshoot:
1. Install a 3000 psi pressure gauge into pres-
b. Fully retract and dead-head tilt cylinders.
sure check (PC1, Illustration 22-11).
c. Observe the pressure gauge at 2100 rpm.
2. Fully steer tires to one side or the other and
The pressure gauge should read 2900 psi.
refer to the Pressure Setting section of the
steer sensing valve for the proper steer pres- d. Shut truck down and install a flowmeter in
sure reading. the 1-1/4” hose connected to the inlet sec-
tion.
3. If pressure is low:
e. Start truck and the flowmeter should indi-
a. Remove the hose from the low pressure
cate approximately 62 gpm (at 2100 rpm)
side of the steer cylinder. The low pres-
of flow.
sure side is the side which the steer cylin-
der rod is extended from. Cap the hose. 2. Tilt Section
b. Steer the truck in the same direction as in a. Install an appropriate pressure gauge into
procedure 2. so as to dead-head the fluid pressure check (PC1, Illustration 22-11).
against the packing.
b. Fully retract and dead-head tilt cylinders.
c. There should be minimum fluid flow
c. Observe the pressure gauge at 2100 rpm.
through the open port.
The pressure gauge should read 2900 psi.
d. If fluid flow is excessive, fluid is bypassing The main relief valve located in the inlet
22-16 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
section controls this pressure. oughly lubricated and to reach the same tempera-
ture as the fluid.
d. Fully extend and dead-head the tilt cylin-
ders. Hydraulic System Troubleshooting (Illustration
22-15)
e. Observe the pressure gauge at 2100 rpm.
The gauge should read 2500 psi. One of the most misunderstood systems is the
hydraulic system incorporated in industrial trucks.
3. Lift Section
What appears to be a simple failure of a compo-
a. Install an appropriate pressure gauge into nent is usually corrected by replacement of that
pressure check (PC2, Illustration 22-11). component, without due regard to the cause of
the failure. There may be several individual sys-
b. Fully extend and dead-head the lift cylin-
tems such as lift, steer, and attachment tied
ders.
together to become one overall hydraulic system.
c. Observe pressure gauge at 2100 rpm. In which event, what happens to one subsystem
The pressure gauge should read 2900 psi. may affect every other subsystem. Therefore, it is
absolutely necessary that special attention be giv-
4. Outlet Section
en to pressures and cleanliness.
a. Install a flowmeter in the 1-1/2” hose con-
The most meaningful system check a serviceman
nected to outlet section.
can use in diagnosing a problem is the check of
b. The flowmeter should indicate approxi- the hydraulic circuit pressure on any machine that
mately 124 gpm at 2100 rpm (no hydraulic uses hydraulic components. The two cardinal
functions being operated). rules that should be followed are:
Lift / Tilt Valve Summary. All of the procedures 1. Excessive pressure does not offer any opera-
that have been listed to troubleshoot the lift / tilt tional advantage. It only shortens component
valve are for normal operation. Should abnormal life.
operation of the hydraulic system be detected,
2. Pressure just high enough to achieve compo-
you must be capable of isolating the fault, whether
nent function is always the most desirable set-
it be upstream or downstream. Listed below are
ting.
some guidelines to consider:
We must also remember that the only reasons for
1. Restrictions in hydraulic circuits will increase
making a hydraulic pressure check are to verify
pressure downstream and decrease flow rate
that the system is to specifications or to trouble-
upstream.
shoot the system to pinpoint a malfunction.
2. In order to build pressure, the flow must be Before an accurate reading can be obtained the
restricted to the circuit. following steps must be taken:
Replacement of Pump 1. The hydraulic fluid must be to Taylor specifica-
tions. Any fluid not to these specifications can
give a faulty reading.
If a pump or valve is being
replaced, always take a preliminary pressure 2. The hydraulic system should have been run
reading of the cold fluid, at idle rpm, because if long enough to bring the system temperature
there is a malfunctioning pressure relief valve to approximately 125_ to 150_F (51.6_ to
in the system, it can burst the pump housing. 65.5_C).
Normally, if a cylinder is dead-headed, the One of the best ways to attain this tempera-
engine will stop before bursting the pump. If ture is to dead-head a cylinder for a short peri-
your gauge reading begins to exceed the maxi- od of time, passing fluid over the relief valve to
mum allowed pressure, do not dead-head the generate heat.
function completely. 3. It is extremely important that pressure read-
ings on Taylor equipment be taken at the point
When a new pump is installed, allow the engine to and engine speed specified. If the pressure
idle for 15 or 20 minutes before pressurizing the gauge is installed at another point in the sys-
system. This allows the pump to become thor- tem, readings other than the correct one can
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 22-17
or will be obtained due to back pressure and vehicle engine is running at the recommended
other causes. It should be noted that readings rpm (refer to Illustration 22-15 for the Pressure
for accuracy should be obtained when the Setting Chart).
1. No lift or tilt 1. Low pilot pressure. 1. Refer to Problem 7. of this trouble-

shooting chart.
2. Low hydraulic fluid flow. 2. Refer to Problem 9. of this trouble-
shooting chart.
3. Worn or damaged main pump. 3. Repair or replace main pump.
2. No tilt in or slow 1. Low pilot pressure. 1. Refer to Problem 7. of this trouble-

tilting in shooting chart.
shooting chart.
3. Spool in the work section is 3. Remove spool, visually inspect
sticking. spool and spool housing for debris.
4. Fluid is bypassing in the tilt cylinder 4. Isolate and repack tilt cylinders. To
piston packing. isolate the defective cylinder, per-
form the following:
a. With the tilt cylinders fully
retracted and dead-headed,
disconnect the hydraulic hoses
from the piston ends of the tilt
cylinders and plug.
b. Shift the joystick to the tilt back
position.
c. Observe the open ports on the
piston ends of the tilt cylinders.
If a flow of fluid is detected from
either of the tilt cylinders, this is
the bad cylinder and requires
repacking.
5. Incorrect main relief valve pressure 5. Set main relief valve for correct
setting. pressure.
6. Defective main relief valve. 6. Replace main relief valve.
3. No tilt out or slow 1. Low pilot pressure. 1. Refer to Problem 7. of this trouble-
tilting out shooting chart.
shooting chart.
continued sticking. spool and spool housing for debris.
22-18 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
3. No tilt out or slow 4. Fluid is bypassing in the tilt cylinder 4. Repack the tilt cylinder.
tilting out piston packing.
(Continued)
setting. pressure.
7. Incorrect tilt relief valve pressure 7. Set tilt relief valve for correct
setting (in port A). pressure.
8. Incorrect tilt relief valve pressure 8. Refer to Problem 4. of this trouble-
setting or defective tilt lock valve shooting chart
(mast will rack).
4. Mast racks 1. Improper tilt lock valve pressure 1. Refer to Tilt Lock Valve in the Set-
relief setting. ting Hydraulic Pressures of this
section.
5. No lift or slow 1. Low pilot pressure. 1. Refer to Problem 7. of this trouble-

lifting shooting chart.
shooting chart.
sticking. spool and spool housing for debris.
4. Fluid is bypassing the lift cylinder 4. Isolate and repack lift cylinders. To
piston packing. isolate the defective cylinder, per-
form the following:
a. Remove the vent hydraulic
hoses from the rod ends of the
lift cylinders.
b. Fully extend and dead-head
the lift cylinders.
rod ends of the lift cylinders. If
a flow of fluid is detected from
either of the lift cylinders, this is
the bad cylinder and requires
repacking.
setting. pressure.
7. Incorrect mid-inlet relief valve pres- 7. Set mid-inlet relief valve for the cor-
sure setting. rect pressure.
continued 8. Defective mid-inlet relief valve. 8. Replace mid-inlet relief valve.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22-19

5. No lift or slow 9. Vent hoses to the lift cylinders are 9. Reposition vent hoses at the
lifting (Continued) positioned at the hydraulic fluid hydraulic tank.
level in tank.
6. No lowering or 1. Amber container light is illumi- 1. This is proper operation.

slow lowering nated.
2. Defective lift soft landing solenoid. 2. Replace lift soft landing solenoid.
3. Defective lift soft landing solenoid 3. Replace lift soft landing solenoid
cartridge. cartridge.
4. Defective lift soft landing solenoid 4. Replace lift soft landing solenoid
valve. valve.
5. Low pilot pressure. 5. Refer to Problem 7. of this trouble-
shooting chart.
6. Spool in work section is sticking. 6. Remove spool, visually inspect
spool and spool housing for debris.
7. Defective flow regulator in one of 7. Replace flow regulator.
the lift cylinder.
7. Low or no pilot 1. Seat belt is not fastened. 1. Fasten seat belt.

pressure
2. Defective seat belt relay (K20). 2. Replace seat belt relay.
3. Red or green container light is not 3. Refer to Red Light Operation
illuminated. (Unlocked) or Green Light Opera-
tion (Locked) in this section to
troubleshoot.
4. Circuit breaker (CB15) is tripped or 4. Refer to Circuit Breakers in the
defective. Component Troubleshooting in
Section 6.
5. Defective diode bank. 5. Replace diode bank.
6. Incorrect pilot relief valve pressure 6. Adjust pilot relief valve for correct
setting (located in port 3 of the pressure (250 psi).
brake manifold valve).
7. Defective pilot relief valve (located 7. Replace pilot relief valve.
in port 3 of the brake manifold
valve).
8. Incorrect pressure reducing valve 8. Set pressure reducing valve for
pressure setting (located in port 1 correct pressure (400 psi).
of the brake manifold valve).
9. Defective pressure reducing valve 9. Replace pressure reducing valve.
(located in port 1 of the brake man-
ifold valve).
continued
22-20 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

7. Low or no pilot 10. Defective seat belt switch. 10. Replace seat belt.
pressure
(Continued) 11. Defective controller enable sole- 11. Refer to Solenoids in the Compo-
noid or cartridge. nent Troubleshooting in Section
6 to determine whether the sole-
noid coil or cartridge is defective.
12. Loose, broken or shorted wire(s) 12. Isolate and repair wire(s) #38, #79
#38, #79 or #289. or #289.
13. Loose or crimped pilot pressure 13. Isolate and repair.
hose.
14. Loose connection or pin broken at 14. Isolate and repair.
electrical connector.
15. Defective brake manifold valve. 15. Replace brake manifold valve.
16. Defective controller enable sole- 16. Replace the controller enable sole-
noid valve. noid valve.
17. Defective controller valve. 17. Replace controller valve.
18. Worn auxiliary (spreader / brake) 18. Replace or rebuild pump.
pump.
8. Low or no pilot 1. Refer to Problem 7. of this trouble- 1. Refer to Problem 7. of this trouble-
pressure (if shooting chart. shooting chart.
equipped with cab
tilt system) 2. Fluid is bypassing in the cab tilt cyl- 2. Isolate and repack cab tilt cylin-
inder piston packing. ders. To isolate the defective cylin-
der, perform the following:
a. With the cab and mast down,
disconnect the hydraulic hoses
from the piston ends of the cab
tilt cylinders and plug.
b. Energize the cab tilt switch
(S21).
piston ends of the cab tilt cylin-
ders. If a flow of fluid is
detected from either of the cyl-
inders, this is the bad cylinder
and requires repacking.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22-21

9. Low or no hydrau- 1. Low hydraulic fluid supply. 1. Fill tank to the correct fluid level.
lic fluid flow
2. Cold hydraulic fluid. 2. Due to extended periods of cold
temperatures, the viscosity of the
hydraulic fluid can increase. Con-
sider adding a cold weather pack-
age.
3. Breather filter(s) plugged. 3. Replace the breather filter(s).
4. Incorrect type of fluid. 4. Drain and flush hydraulic circuits.
Refer to the Fuel and Lubricant
Specifications in the Appendices.
5. Clogged suction strainer. 5. Clean suction strainer.
6. Low pilot pressure. 6. Refer to Problem 7. of this trouble-
shooting chart.
7. Air leak in suction hose to pump. 7. Locate leak and repair.
8. Worn / defective pump. 8. Replace or rebuild pump.
9. Stripped flex plate on transmission. 9. Replace flex plate.
22-22 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 22-14. Main Hydraulic Circuit
22-2834 SHT. 01
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 22-23
Hoist Circuit
22-24 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Hoist Circuit
PLACE THE FOLLOWING ILLUSTRATION IN

A FOLDER ENVELOPE:
Illustration 22-15 - 22 2834 SHT. 2 (ANSI)
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 3/05)

06/03) 22-25
22-26 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)
22D-Cab Tilt System
Section 22D
Cab Tilt System

Introduction. The cab tilt system controls the tilting Hydraulic fluid from the rod end of the tilt cylinders
of the truck cab. is vented back through the A ports through a flow
restrictor which will restrict the flow back to the
Major Components (Illustration 22D-3). The major
hydraulic tank.
components of the cab tilt system consists of a
auxillary (spreader / brake) pump, brake manifold Manual Override (Illustration 22D-1). The cab tilt
valve, cab tilt solenoid valve, cab tilt cylinders, solenoid valve is equipped with a manual override
hoses and various fittings. knob. In the event of an electrical failure, the knob
of the cab tilt solenoid valve can be pushed in and
Main Steering Pump. Refer to Section 22 for a
rotated clockwise to shift the main spool, sending
detailed description of how the main steering pump
flow out the B ports, overriding solenoid (S1) to tilt
works.
the cab. The knob can be pulled out and turned
Brake Manifold Valve (Illustration 15C-1). Refer counterclockwise to shift the spool, sending flow out
to Section 15C for a detailed description of how the A ports, overriding solenoid (S2) to lower the
the brake manifold valve works. cab. The manual override knob must be adjusted
Cab Tilt On / Off Rocker Switch (S21, Illustration to its neutral position, after either of the two proce-
29-2). Push the switch forward to enable the cab dures above have been performed to allow normal
tilt circuit; push the switch rearward to disable the operation of the cab tilt solenoid valve. The neutral
cab tilt circuit. position allows the manual override knob to free-
spin in either direction and can be move in and out
Cab Tilt Solenoid Valve (Illustrations 22D-1 and (approximately 1/4”).
22D-3). The cab tilt solenoid valve is located
underneath the cab, located above the engine on Cab Tilt Cylinders (Illustration 22-1). The cab tilt
the left-hand side. It is controlled by the cab tilt cylinders are double-acting. They alternately
switch (S21) and proximity switch (S52). With the receive pressurized fluid on one side of the piston,
cab tilt switch (S21) energized, 12 VDC will be while the fluid on the other side returns to the
applied to S52 on the white and red wires (wire hydraulic tank. To change the cab tilt cylinder
#26). S52 is targeting the inner mast. If the mast is direction, the pressurized and vented sides of the
fully lowered, S52 will be energized (L.E.D. is illumi- piston are exchanged through the valving.
nated on the back of the proximity switch). 12 VDC Hydraulic Hose Assemblies and Fittings. All
on the white wire will be sent out the orange wire of hydraulic hose assemblies should be checked daily
S52 through wire #74 to solenoid (S2) of the cab tilt for chafed or cracked hoses. Check daily to ensure
solenoid valve, energizing the solenoid. Once the that there are no loose fittings on the hydraulic
solenoid is energized and the spool has shifted, the connections.
pilot pressure at the P port of the cab tilt solenoid
valve will be sent around a flow restrictor and out Cab Tilt / Flow Control Adjustment (Illustrations
the A ports to the rod end of the cab tilt cylinders, 22D-1 and 22D-3). The cab’s lifting and lowering
retracting the cab tilt cylinders. Hydraulic fluid from speeds can be adjusted for desired speed. Perform
the piston end of the tilt cylinders is vented back procedure 1. to change the lifting speed or proce-
through to the B ports through a flow restrictor dure 2. to change the lowering speed.
which will restrict the flow back to the hydraulic tank. 1. Perform the following procedures to increase
When the proximity switch (S52) loses its target or decrease the lifting speed:
(inner mast) and the cab tilt switch (S21) is ener- a. Loosen the locknut on the 1-1 port flow con-
gized, S52 will de-energize (L.E.D. is not illumi- trol cartridge of the cab tilt solenoid valve.
nated) and 12 VDC on the white wire will be sent
out the blue wire of S52, down wire #75 to sole- b. Turn the setscrew of the flow control car-
noid (S1) of the cab tilt solenoid valve. Once the tridge counterclockwise to increase the lifting
solenoid is energized and the spool has shifted, speed or clockwise to decrease the lifting
pilot pressure at the P port of the cab tilt solenoid speed.
valve will be sent around a flow restrictor and out c. Once the desired speed has been obtained,
the B ports and to the piston end of the cab tilt cyl- tighten the locknut.
inders, extending them and tilting the cab.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 7/05)

06/03) 22D-1
CONNECTOR
(CTC2)
CONNECTOR
(CTC1)
PRESSURE
CHECK
(CPCP)
SOLENOID
PRESSURE (UP)
CHECK (S1)
(CPCB)
MANUAL
OVERRIDE
PRESSURE SOLENOID KNOB
CHECK (DOWN)
(CPCA) (S2)
INDICATES HYDRAULIC FLOW
Illustration 22D-1. Cab Tilt Solenoid Valve
22D-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

2. Perform the following procedures to increase tridge counterclockwise to increase the lifting
or decrease the lowering speed: speed or clockwise to decrease the lifting
speed.
a. Loosen the lock nut on the 1-2 port flow
control cartridge of the cab tilt solenoid c. Once the desired speed has been obtained,
valve. tighten the locknut.
b. Turn the setscrew of the flow control car-
Cab Tilt System Troubleshooting (Illustrations 22D-2 and 22D-3)
1. Cab will not tilt 1. Cab tilt switch (S21) is in the off 1. Turn cab tilt switch (S21) on.
position.
2. Proximity switch (S52) is energized. 2. Cab tilt switch (S21) only supplies
12 VDC to the proximity switch
(S52). It does not energize sole-
noid (S1) of the cab tilt solenoid
valve. Only when S52 de-ener-
gizes will the cab tilt automatically.
in the Component Troubleshoot-
ing in Section 6.
4. Loose, broken or shorted wire(s). 4. Isolate and repair wire(s).
5. Defective cab tilt switch (S21). 5. Replace cab tilt switch (S21).
6. Defective proximity switch (S52). 6. Replace proximity switch (S52).
Refer to 30mm Proximity Switches
ing in Section 29.
7. Defective cab tilt solenoid valve 7. Refer to Solenoids in the Compo-
solenoid (S1) or cartridge. nent Troubleshooting in Section 6
to determine whether the solenoid
coil or cartridge is defective.
8. Defective cab tilt solenoid valve. 8. Replace cab tilt solenoid valve.
9. Spool sticking in the cab tilt sole- 9. Repair or replace cab tilt solenoid
noid valve. valve.
2. Cab will tilt slowly 1. Low pilot pressure. 1. Check and adjust pilot pressure
(400 psi) if required.
2. Hydraulic fluid is bypassing the tilt 2. Repack tilt cylinder.
cylinder packing.
3. Spool sticking in the cab tilt sole- 3. Repair or replace cab tilt solenoid
noid valve. valve.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22D-3

3. Cab will not come 1. Cab tilt switch (S21) was turned off 1. Turn cab tilt switch (S21) on.
down after the cab fully tilted.
2. Proximity switch (S52) is de-ener- 2. Cab tilt switch (S21) only
gized. supplies 12 VDC to the proximity
switch (S52). It does not energize
solenoid (S2) of the cab tilt sole-
noid valve. Only when S52 ener-
gizes will the cab come down auto-
matically.
3. Circuit breaker (CB18) is tripped or 3. Refer to Correction 3. of Problem 1.
defective.
5. Defective cab tilt switch (S21). 5. Replace cab tilt switch (S21).
6. Defective proximity switch (S52). 6. Replace proximity switch (S52).
Refer to 30mm Proximity Switches
ing in Section 29.
7. Defective cab tilt solenoid valve 7. Refer to Solenoids in the
solenoid (S2) or cartridge. Component Troubleshooting in
Section 6 to determine whether
the solenoid coil or cartridge is
defective.
8. Defective cab tilt solenoid valve. 8. Replace cab tilt solenoid valve.
9. Defective flow control cartridge of 9. Replace or repair flow control
the cab tilt solenoid valve. cartridge.
22D-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 22D-2. Cab Tilt Hydraulic Circuit
22D-0019 SHT. 01
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22D-5

Illustration 22D-3. Cab Tilt Hydraulic ANSI Circuit
22D-0019 SHT. 02
22D-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

22E-Accumulator
Section 22E
Accumulator
Introduction. The accumulator acts as a shock Charging The Accumulator (Illustration 22E-1).
absorber in the hydraulic system. When the driv- Perform the following procedures to charge the
en member of the hydraulic system stops sudden- accumulator:
ly, it creates a pressure wave that travels back
through the system. This shock wave can devel-
op peak pressures several times greater than nor-
mal working pressures and can be the source of S Use only dry nitrogen to charge the
system failure. The gas cushion in an accumula- accumulator.
tor will minimize this shock, protecting expensive S When precharging, the initial 50 psi of dry
hydraulic components. nitrogen should be introduced slowly into
Accumulators. There are two accumulators used the accumulator.
in the hydraulic circuits of this truck. These accu- 1. Install the charging kit (Illustration 22E-1) as
mulators are hydro-pneumatic piston type accu- explained in the Checking Precharge proce-
mulators which are precharged with dry nitrogen. dures above.
One of the accumulators is located below the
main control valve (see Illustration 22-1) while the 2. Connect the charging kit to a nitrogen bottle
other is attached to the main frame of the attach- with the charging hose (8).
ment (see Illustration 29-13). The accumulator, 3. Inflate the accumulator to the predetermined
located on the truck, is precharged to 1250 psi pressure by opening the valve on the nitrogen
while the attachment accumulator is precharged to bottle slowly, closing it occasionally to allow
65 psi. the needle of the pressure gauge (2) to settle
Checking Precharge. The precharge check into position giving an accurate pressure read-
should be performed monthly or every 250 hours, ing.
whichever comes first. Follow the procedures 4. When the proper precharge pressure is
listed below to check precharge (a charging kit is reached, close the valve on the nitrogen
available from Taylor, part number 1000-503). bottle.
See Illustration 22E-1 for charging kit.
1. To read and adjust the gas pressure or “pre- 5. To release pressure in excess of the desired
charge” pressure, all of the hydraulic fluid must precharge, slowly open the bleeder valve (6)
be drained from the fluid side of the accumula- until the pressure drops to the desired level.
tor to zero hydraulic pressure. To accomplish 6. Rotate the bar handle counterclockwise to the
this, let the lift cylinder down and hold lever in full stop position and then disconnect the swiv-
the DOWN position for approximately one min- el (7) from the adapter (3).
ute.
7. Remove the air chuck (4) from the accumula-
2. Remove the valve guard and cap from the tor valve stem.
accumulator.
8. Check the valve stem for leaks with a soapy
3. Ensure that the shaft of the air chuck (4) is ful- water solution or oil. If the core is leaking,
ly retracted by turning the bar handle counter- depress it quickly, once or twice, to reseat the
clockwise until it stops. core. It may be necessary to further tighten or
4. Do not have the charging hose (8) connected replace the core if leakage persists.
to the gauging head assembly (1) unless free 9. Install the accumulator valve stem cap, then
end of charging hose is plugged. tighten 1/2 turn beyond hand tight.
5. Mount the swivel of the air chuck (4) on the 10. Install the accumulator valve guard.
accumulator’s valve stem and hand tighten to
compress the gasket in the swivel to prevent 11. Recheck precharge one week after charging
gas leakage. for pressure loss.
6. Turn the bar handle clockwise until the shaft
depresses the valve stem core of the accumu-
lator. The precharge pressure should now be
indicated by the pressure gauge (2).
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 22E-1

Accumulator Part Number / Size Precharge
2215-121 / 1 qt. 1000 psi
2 2788-970 / 1 qt. 1000 psi
2215-124 / 1 qt. 1500 psi
3 2788-955 / 1 qt. 1500 psi
BAR
7 1
HANDLE 2788-940 / 1 gal. 65 psi
4 2788-960 / 1 gal. 800 psi

2788-949 / 1 gal. 1250 psi
5 2788-950 / 1 gal. 1000 psi
8 2788-951 / 1 gal. 1500 psi
2788-952 / 1 gal. 1500 psi
2788-953 / 1 gal. 1500 psi
2788-961 / 1 gal. 1500 psi
2788-965 / 2-1/2 gal. 800 psi
6 ACCUMULATOR 2788-966 / 2-1/2 gal. 1500 psi
9 11 We have a charging kit available. Taylor part

10
number 1000-503.
NITROGEN
BOTTLE
Charging Kit
1. GAUGING HEAD ASSEMBLY
2. PRESSURE GAUGE
3. ADAPTER
4. AIR CHUCK
5. TANK VALVE ASSEMBLY
6. BLEEDER VALVE
7. SWIVEL CONNECTOR
8. CHARGING HOSE
9. COUPLING
10. GLAND
11. GLAND NUT
Illustration 22E-1. Charging Accumulator
22E-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Section 27
Mast Assembly
Introduction. The mast assembly, in conjunction Maintenance / Inspections. There are several
with the carriage and container attachment, is inspectional requirements which must be per-
responsible for lifting and lowering loads. formed daily. These inspections must include
Major Components. The mast assembly consists checking all welds and structural members for
of the inner mast, outer mast, two hydraulic lift cyl- cracks. Check all mast mounting hardware and lift
inders, main rollers, chain rollers, slide bearing chains for damage or loose bolts. Hydraulic
blocks, backrest slide blocks and two multiple leaf hoses and fittings must be checked for leaks and
lift chains. signs of wear or damage.
Structural Inspection and Reporting Procedure
(Refer to SIRR in the Appendices). Follow the

OSHA rules, 29 CFR, 1910.178 (Q)(1), (5), & (7) S Do not climb on the mast of the lift truck, on
which require inspecting industrial trucks daily top of the cab or on other high places of the
before being placed in service, removing trucks truck while performing maintenance.
from service if cracks are found, and making S Always use OSHA approved ladders, stands,
repairs only if authorized by the manufacturer. If or manlifts to reach high places on the truck.
trucks are used on a round-the-clock basis, they
shall be examined after each shift. OSHA 29 CFR S Do not use a material handling lift truck as a
1910.178 (p)(1) requires that trucks in need of means to elevate personnel.
repair be taken out of service. Main Rollers (Illustration 27-4). The main rollers
Mast Assembly Structure. This is a nested chan- of the inner mast employ greaseable, shielded,
nel type mast with two multiple leaf lift chains and tapered roller bearings for increased durability. The
two lift cylinders that are located behind the mast main rollers must be greased monthly or every
rails. The mast assembly is carefully engineered 250 hours, whichever comes first. To access the
and ruggedly constructed, although welded steel grease fittings for the main rollers, the inner mast
structures always contain undetectable cracks, must be raised so that the grease fitting of each
especially welded joints. When these joints are main roller aligns with the grease holes located in
subject to fluctuating stresses of significant magni- the outer mast (refer to the Lubrication section in
tude, these cracks will grow. This is known as the Appendices). The main rollers should be
fatigue crack growth. No matter how low the inspected for flat spots or evidence of sliding any
stress levels are kept, some fatigue crack growth time the inner mast is taken apart from the outer
will occur in all welded structures. mast.

The roller assemblies must not
S Periodic inspection is required to detect be over lubricated. Excess grease inside the
fatigue cracks that have grown to a signifi- mast rails may cause the rollers to slide when
cant size in order to avoid serious failure of subjected to a heavy load. If this happens, a
the structural weldment. When a crack is flat spot will be worn on the rollers and the
found, the truck must be immediately taken rollers will continue to slide until replaced with
out of service and repaired. new rollers.
S Under no circumstances, without prior Chain Rollers (Illustration 27-4). The chain rollers
approval from Taylor Machine Works, Inc. use sealed ball bearings. Check the chain rollers
Engineering Department, should the mast for looseness, cracks or flat spots.
assembly be modified. As per OSHA 29 Slide Bearing Blocks Shimming (Illustrations
CFR1910.178 (a) (4). 27-1 and 27-3). The slide bearing block life
S If the fatigue crack is allowed to grow, cata- depends on the duty cycle and operation of the
strophic failure could occur in the mast truck. Periodically, the slide bearing blocks may
assembly or other welded components caus- require shimming to adjust for wear. To prevent
ing serious injury to personnel and / or prop- undue flexing of the inner mast on a telescopic
erty. mast assembly, it is essential for all slide bearings
to be properly shimmed. Perform the following
procedures to correctly shim the mast assembly.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 27-1

PROCEDURE 2
PROCEDURE 3
PROCEDURE 1
PROCEDURE 4
PROCEDURE 5
Illustration 27-1. Mast Slide Bearing Shimming Procedure

1. Raise the carriage to allow enough room to 3. Raise the carriage until the bottom carriage
install shims in the outer mast slide bearings. slide bearings are aligned with the outer mast
The carriage and inner mast should then be slide bearings. Pry the carriage from side to
secured in position by an appropriate means side and measure the movement. The car-
or they can be lowered to a height where they riage and inner mast should then be secured
can more easily be blocked in position and in position by an appropriate means or they
shimmed. Shim the outer mast until the clear- can be lowered to a height where they can
ance is 1/16” to 1/32”. (See NOTE below pro- more easily be blocked in position and
cedure 5.) shimmed. Calculate the thickness of the
shims needed by subtracting 1/32” from the
2. Raise the carriage until the top carriage slide
distance the carriage moved and shim the bot-
bearings are aligned with the outer mast slide
tom carriage slide bearings. (See NOTE
bearings. Pry the carriage from side to side
below procedure 5.)
and measure the movement. The carriage
and inner mast should then be secured in 4. Align the bottom carriage slide bearings and
position by an appropriate means or they can the inner mast top slide bearings. Pry the
be lowered to a height where they can more inner mast from side to side (this must be
easily be blocked in position and shimmed. done from the rear of the mast) and measure
Calculate the thickness of the shims needed the movement. Calculate the thickness of the
by subtracting 1/32” from the distance the car- shims needed by subtracting 1/32” from the
riage moved and shim the top carriage slide distance the inner mast moved. Raise the car-
bearings. (See NOTE below procedure 5.) riage to allow access to the inner mast top
slide bearings. The carriage and inner mast
27-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

should then be secured in position by support- Care, Maintenance, and Replacement section in
ing with an appropriate means. (See NOTE the Appendices). Refer to the Lubrication sec-
below procedure 5.) tion in the Appendices for the type of lubricant to
be used to lubricate the lift chains.
5. Align the bottom carriage slide bearings and
the inner mast bottom slide bearings. Pry the Lubrication. Refer to the Lubrication section in
inner mast from side to side (this must be the Appendices for information on the lubrication
done from the rear of the mast) and measure of the mast assembly.
the movement. Calculate the thickness of the
shims needed by subtracting 1/32” from the
distance the inner mast moved. Raise the car-
riage to allow access to the inner mast bottom
slide bearings. The carriage and inner mast
should then be secured in position by support-
ing with an appropriate means. (See NOTE
below)
NOTES:
S Clearance at each position should be between
1/16” and 1/32”. Repeat the above procedure
if the clearance is not as specified. Shims
should be divided as evenly as possible
between the slide bearings.
S Replace any slide bearing blocks that
become cracked, damaged or worn to 1 - 3/4”
thickness (see Illustration 27-3).
Do Not attempt to eliminate

inner mast slide bearing slack in procedures 4.
and 5. by adding shims to the carriage slide
bearings. This can result in broken slide
bearings.
Back Rest Slide Blocks (Illustrations 27-2). The
back rest slide block life depends on the duty
cycle and operation of the truck. Periodically, the
back rest slide blocks may require shimming to
adjust for wear. Perform the following procedures
to shim the back rest slide blocks:
1. Raise the carriage and note the position of the
inner mast when the distance between it and
the back rest slide block is the least amount.
Shims should be added at this position.
2. Shim the back rest slide blocks until the slide
blocks just touch the inner mast.
NOTE: Replace any slide bearing blocks that
become cracked, damaged or worn to 1” thick-
ness.
Lift Chains. The lift chains must be lubricated
every 500 hours of operation (refer to Leaf Chain
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 27-3

INNER MAST
OUTER MAST
BACK REST
SLIDE BLOCK
Illustration 27-2. Back Rest Slide Blocks
Troubleshooting
1. Cracks in Welds, 1. Metal fatigue. 1. Have cracks in welds repaired

especially at the immediately.
point where the
mast is pinned to 2. Overloading. 2. Refer to Correction 1. and avoid
the chassis. overloading the truck.
(Refer to SIRR in the 3. Rough terrain. 3. Refer to Correction 1. and, if pos-
Appendices) sible, avoid operating truck on
rough terrain.
Notify Taylor
Machine Works, 4. Travelling with load in an unrecom- 4. Refer to Correction 1. and the
Inc. for proper mended travel position (excessive Operator’s Guide for proper travel-
repair procedures. height and / or fully side-shifted, ling positions.
one side or the other).
5. Severe duty cycles. 5. Have cracks in welds repaired
immediately.
27-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

MAST RAIL
SHIM
SLIDE BEARING HOUSING
SLIDE BEARING BLOCK
CRACKED OR
DAMAGED SLIDE
BEARING BLOCK
1-3/4” MINIMUM
REPLACE BEARING BLOCKS
WORN TO 1-3/4” THICK OR BLOCKS
THAT ARE CRACKED OR BROKEN
Illustration 27-3. Slide Bearing Block Replacement
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 27-5

OUTER MAST BACKREST
SLIDE BEARING SLIDE BEARING
BLOCK BLOCK
CHAIN
ROLLER LIFT
CYLINDER
INNER MAST
OUTER MAST
INNER MAST
MAIN ROLLERS
SLIDE
BEARING
BLOCKS
Illustration 27-4. Mast Assembly Components
27-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Note: Photocopy this sketch to identify fatigue cracks or
structural damage to the mast assembly. Be very descriptive
of damage to the mast assembly, i.e. location, depth, length.
Illustration 27-5. Mast Assembly
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 27-7

Lift Chain Installation (Illustrations 27-6 through 6. Tighten the mast chain anchor nuts until 2” of
27-8). Perform the following procedures to install thread remains visible below the lower nut.
the lift chains.
7. Slowly lower the lifting device until all the chain
weight is supported by the mast chain anchor.

S Death or serious injury could result from a 8. Remove the lifting device and choker from the
runaway truck. Park the truck on a hard, lift chain and connect this end to the carriage
level surface, block wheels in both chain anchor.
directions to prevent movement of the truck
and apply the parking brake.
S Do not climb on the mast of the lift truck, on
top of the cab or other high places of the
truck while performing maintenance.
S Always use approved ladders, stand, or CARRIAGE
manlifts to reach high places on the truck.
S Do not use a material handling lift truck as a UPPER
means to elevate personnel. ANCHOR
NUT
1. Park the truck on a hard, level surface, block
wheels in both directions to prevent movement
of the truck and apply the parking brake. LOWER
ANCHOR
2. Provide an appropriate lifting device capable NUT
of lifting the length of chain (Approximately
1,000 lbs). ANCHOR
3. Attach an appropriate choker in the center of THREADS
the chain length.
4. Lift the chain from the front side of the mast Illustration 27-7. Carriage Chain Anchor
until the end is level with the chain roller.
5. Slide or pull one end of the chain over the roll- 9. Tighten the carriage chain anchor nuts until
er and attach it to the mast chain anchor. 1.5” of thread remains visible below the lower
nut.
CHAIN
MAST
UPPER
ANCHOR
NUT
LOWER
ANCHOR
NUT
CHAIN
ANCHOR ROLLER
THREADS
Illustration 27-6. Mast Chain Anchor Illustration 27-8. Chain Roller
27-8 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
1/05)
10. Run the mast up and down several times to 3. If adjustment is required, check the deflection
allow the lift chains to find their travel paths of each lift chain. The deflection of each lift
over the respective chain roller. The chain will chain should be approximately the same. On
not necessarily center up on the chain roller. each chain at the approximate mid point, apply
the same force in the direction of chain articu-
Lift Chain Adjustment (Illustrations 27-9 through
lation (see Illustrations 27-10 and 27-11).
27-11). The lift chains will periodically require
adjustments to compensate for wear.
1. Park the truck on a hard, level surface and
apply the parking brake.
LIFT CHAINS
CARRIAGE
APPROXIMATE
MID POINT
OUTER ALIGNMENT INNER

MAST MAST
Illustration 27-9. Mast Assembly Alignment
2. If the lift chains are properly adjusted, the

outer mast, inner mast and carriage will be
aligned (see Illustration 27-9). Illustration 27-11. Mast Assembly
4. Should the deflection differ, position the

attachment on a container. When the yellow
on container light illuminates, rotate the twist-
lock override switch to the on position and
continue to lower the attachment until the lift
chains go slack.
APPLIED
FORCE DEFLECTION 5. Loosen the lower nut on the chain anchor of
the slacker lift chain anchor and rotate the
upper nut clockwise to decrease chain deflec-
tion. Tighten the lower nut to lock the upper
nut into position.
6. Lift the attachment off the container and
repeat procedures 3. through 5. if required.
Illustration 27-10. Deflection
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.2/05)
06/03) 27-9
1-12 RTGP-9042N (9/01)
Section 29
Container Attachment
SLIDER BEAM
TRUCK SIDE
CARRIAGE
RIGHT
SUB-TROLLEY
WIDE
EXPANSION FRAME NARROW
EXPANSION FRAME
MAIN FRAME
LEFT
TWISTLOCKS
Illustration 29-1. Attachment Components Locations
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-1

Introduction. The container attachment is a top lift end) of the left slew cylinder to retract the cylinder
attachment that is constructed of high-strength steel (or extend the cylinder).
and features side-shift adjustment. Hydraulic cylin- Right Slew Circuit Operation (Illustration 29-24).
ders provide sufficient force to slide the attachment, To perform the slew function depress the right in
complete with load, in either direction. The attach- or out slew switch (S29). 12 VDC will be sent on
ment is equipped with sensors to indicate, by cab- wire #208 (right slew in) or wire #209 (right slew
mounted container lights, when the twistlocks are out) to relay (K12 or K13), energizing the relay’s
fully locked or unlocked and on container. coil. Once the relay coil is energized, 12 VDC will
Major Components. The container attachment be sent from pin 9 to pin 5 on wire #228 (right
consists of the operator controls, safety interlock slew in) or wire #229 (right slew out) to port B or
circuitry, solenoid-operated directional control port A of the left slew work section (WS3) which
valves and the attachment assembly. will shift the pilot control solenoid, allowing pilot
Attachment Assembly. The attachment assem- pressure to shift the main spool. From here, the
bly consists of a three-beam assembly: a main main attachment fluid flow is diverted to the rod
frame, two expansion frames with twistlocks. end (or piston end) of the right slew cylinder to
Refer to Illustration 29-1 for components locations retract the cylinder (or extend the cylinder).
and to the Lubrication section in the Appendices 40 FT. Expand Circuit Operation (Illustration
for attachment lubrication information. 29-25). The twistlocks must be fully unlocked (red
Attachment Proximity Switches Locations. container light illuminated) before 12 VDC operat-
Refer to Illustrations 29-3 and 29-4 for the loca- ing power is supplied to wire #237 for the 40-ft.
tions of the attachment proximity switches. expand switch (S32). To select the 40-ft. position,
depress the 40-ft. expand switch (S32) to the start
Electrical Joystick / Control Stand Switches. position and release. 12 VDC will be sent on wire
Refer to Illustration 29-2 for the location of the #212 to pin 14 of the double-latching relay (K15)
joystick / control stand switches. which will set the relay. Wire #200, which has 12
Side Shift Circuit Operation (Illustration 29-23). VDC on it from a 15 amp circuit breaker (CB20), is
To perform the side shift function, depress the left connected to pins 6 and 10 of K15. In a set state
or right side shift switch (S30). 12 VDC will be (red flag is visible in window), pin 10 is connected
sent on wire #204 (side shift left) or wire #205 to pin 5 while pin 6 is connected to pin 8. In a set
(side shift right) to relay (K8 or K9), energizing the state, 12 VDC will be sent from pin 6 to pin 8 on
relay’s coil. Once the relay coil is energized, wire #251 to port A of the expansion work section
12 VDC will be sent from pin 9 to pin 5 on wire (WS4) which will shift the pilot control solenoid,
#224 (side shift right) or wire #225 (side shift left) allowing pilot pressure to shift the main spool.
to port B or port A of the side shift work section From here, hydraulic fluid flow is diverted to the
(WS1) which will shift the pilot control solenoid, piston end of the expansion cylinders (extending
allowing pilot pressure to shift the main spool. the cylinders).
From here, the main attachment fluid flow is While in the set state, double-latching relay (K15)
diverted to the rod end (or piston end) of the side will close the contact points of pins 10 and 5,
shift cylinders to retract the cylinders (or extend sending 12 VDC out wire #248 to a diode bank
the cylinders). (refer to Diodes in the Component Trouble-
Left Slew Circuit Operation (Illustration 29-24). shooting), energizing the strobe and audible
To perform the slew function depress the left in or alarm. At the same time, 12 VDC on wire #248
out slew switch (S28). 12 VDC will be sent on will be sent to proximity switch S43 (red and white
wire #206 (left slew in) or wire #207 (left slew out) wires) and proximity switch S51 (red wire). When
to relay (K10 or K11), energizing the relay’s coil. proximity switch (S43) senses its target, it will
Once the relay coil is energized, 12 VDC will be energize, connecting the contact points of the
sent from pin 9 to pin 5 on wire #226 (left slew in) white and orange wires. Once this happens,
or wire #227 (left slew out) to port B or port A of 12 VDC is sent out the orange wire #245 to the
the left slew work section (WS2) which will shift white wire #245 of proximity switch (S51). When
the pilot control solenoid, allowing pilot pressure to proximity switch (S51) senses its target, it will
shift the main spool. From here, the main attach- close the contact points of its white and orange
ment fluid flow is diverted to the rod end (or piston wires, sending 12 VDC down wire #246, which will
reset the double-latching relay (K15). Once the
29-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

double-latching relay (K15) resets, it will open the depressing the 20-ft. retract switch (S33) to the
contact points of pins (10 and 5) and pins (6 and stop position. This will send 12 VDC from the
8) removing 12 VDC from wires #248 and #251. retract switch to wire #214 through a diode bank,
If the 40-ft. expansion has been selected, the on wires #244 and #246, resetting the double-
expansion movement can be stopped at any time latching relays (K15 and K16).
by depressing the 40-ft. expansion switch (S32) to Twistlock Circuit Operation (Illustration 29-26).
the stop position. This will send 12 VDC from the The amber container light must be illuminated in
expansion switch down wire #214 through a diode order to lock or unlock the twistlocks. To perform
bank, down wires #244 and #246, resetting the the twistlock lock or unlock function depress the
double-latching relays (K15 and K16). twistlock lock / unlock switch (S31). 12 VDC will
20 FT. Retract Circuit Operation (Illustration be sent on wire #203 (lock twistlocks) or wire #202
29-25). The twistlock must be fully unlocked (red (unlock twistlocks) to relay (K7 or K6). The twist-
container light illuminated) before 12 VDC operat- lock interlock relay (K14) must be energized to
ing power is supplied to wire #237 on the 20-ft. pass ground from pin 5 to pin 9 to pin 13 of relays
expand switch (S33). To select the 20-ft. position, (K6 and K7) which will complete the path for cur-
depress the 20-ft. retract switch (S33) to the start rent flow to relays (K6 and K7) coils, energizing
position and release. 12 VDC will be sent on wire relay (K6 or K7). Once the relay coil is energized,
#213 to pin 14 of the double-latching relay (K16) 12 VDC will be sent from pin 9 to pin 5 on wire
which will set the relay. Wire #200, which has #223 (lock twistlocks) or wire #222 (unlock twist-
12 VDC on it from a 15 amp circuit breaker (CB20) locks) to port A or port B of the twistlock work sec-
and is connected to pins (6 and 10). In a set state tion (WS5) which will shift the pilot control sole-
(red flag is visible in window), pin 10 is connected noid, allowing pilot pressure to shift the main
to pin 5 while pin 6 is connected to pin 8. In a set spool. From here, the main attachment fluid flow
state, 12 VDC will be sent from pin 6 to pin 8 is diverted to the twistlock cylinders to lock or
down wire #252 to port B of the retract work sec- unlock the twistlocks. When the twistlocks are ful-
tion (WS4) which will shift the pilot control solely locked and the attachment is down on a con-
noid, allowing pilot pressure to shift the main tainer, the green and amber container lights will be
spool. From here, the hydraulic fluid flow is illuminated. When the twistlocks are fully
diverted to the rod end of the expansion cylinders unlocked and the attachment is down on a con-
(retracting the cylinders). tainer, the red and amber container lights will be
illuminated. Refer to Attachment Interlock Logic
While in the set state, double-latching relay (K16) For Container Lights Operation for the red,
will close the contact points of pins 10 and 5 green and amber container lights interlock opera-
which will send 12 VDC down wire #247 to a tion.
diode bank (refer to Diodes in the Component
Troubleshooting), energizing the strobe and In the event of an emergency or while mainte-
audible alarm. At the same time, 12 VDC on wire nancing the truck, a twistlock override switch
#247 will be sent to proximity switch S42 (red and (S35) can be held in position to override the inter-
white wires) and proximity switch S50 (red wire). lock (amber container light circuitry) to allow the
When proximity switch (S42) senses its target, it operator to lock or unlock the twistlocks.
will energize, connecting the contact points of the Pile Slope Circuit Operation (If equipped,
white and orange wires. Once this happens, Illustration 29-27). To select the desired pile slope
12 VDC is sent out the orange wire #243 to the function, depress the pile slope switch (S34) to
white wire #243 of proximity switch (S50). When the left down or right down position and hold
proximity switch (S50) senses its target, it will down. 12 VDC will be sent down wire #215 (pile
close the contact points of its white and orange slope left down) or wire #216 (pile slope right
wires, sending 12 VDC down wire #244 which will down) to port A or port B of the pile slope work
reset the double-latching relay (K16). Once the section which will shift the pilot control solenoid,
double-latching relay (K16) resets, it will open the allowing pilot pressure to shift the main spool.
contact points of pins (10 and 5) and pins (6 and From here, the main attachment fluid flow is
8), removing 12 VDC from wires #247 and #252. diverted to the pile slope cylinders to pile slope left
If the 20-ft. retract has been selected, the retract down (right side up) or pile slope right down (left
movement can be stopped at any time by side up).
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-3

ENABLE
SWITCH
(Location
For Earlier
Model HORN
Trucks)
TWISTLOCK
OVERRIDE
SWITCH
Illustration 29-2. Attachment and Lift & Tilt Controls
29-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

RIGHT
S46 S44 S45 S49

(On Container) (Locked) (Unlocked) (On Container)
S50
(Right Frame
20’)
S42
(Left Frame
20’)
S51
(Right Frame
40’)
TRUCK
S43
(Right Frame
40’)
S38 S37 S36 S41

(On Container) (Unlocked) (Locked) (On Container)
LEFT
Illustration 29-3. Proximity Switch Locations (Standard)
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-5

S51
40 FT. EXPAND
PROXIMITY SWITCH
(Wide Frame)
S42
20 FT. RETRACT
PROXIMITY SWITCH
(Narrow Frame)
S50
20 FT. RETRACT
ATTACHMENT END PROXIMITY SWITCH
JUNCTION BOX (Wide Frame)
(RIGHT END)
RIGHT
S43
40 FT. EXPAND
PROXIMITY SWITCH
(Narrow Frame)
TRUCK SIDE
ATTACHMENT END
JUNCTION BOX
(LEFT END)
ATTACHMENT MAIN
JUNCTION BOX
LEFT
NOTE: Refer to Illustration 29-3 for Proximity

Switch locations on Attachment
Illustration 29-4. Attachment Electrical Components
29-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Selecting The 24 Ft. Mode Of Operation extend the attachment to its full 40 ft. position
(Illustration 29-71). When selecting the attach- when transitioning from the 20 ft. mode to the
ment to be operated in the 24 ft. mode, the electri- 24 ft. mode of operation. The attachment
cal components of the frame stops system oper- must be extended past the 24 ft. length to
ates as follows: select the 24 ft. mode of operation.
1. Depress the 40 ft. expansion switch (S32) to De-selecting The 24 Ft. Mode Of Operation
the start position. This places 12 VDC on wire (Illustration 29-71). When de-selecting the attach-
#212. 12 VDC on wire #212 will set relay ment to be operated in the 24 ft. mode, the electri-
(K15). This will place 12 VDC on wire #251 to cal components of the frame stops system oper-
pin 9 of the relay (K52). If all four frame stops ates as follows:
are up, K52 will be energized, connecting pins
1. It is not necessary to extend the attachment to
9 and 5. 12 VDC at pin 9 will pass out pin 5
its full 40 ft. position when transitioning from
down wire #251 to the expansion valve. The
the 24 ft. mode to the 20 ft. mode of operation.
attachment will begin to expand.
The attachment must be extended past the
2. When K52 is de-energized, 12 VDC will pass 24 ft. mode of operation and all four frame
out pin 1 to pins (10 and 6) of relay (K51). stops up to return to the 20 ft. mode of opera-
tion. When all four frame stops are up,
3. Once the attachment has cleared the 24 ft.
12 VDC on the white wire #200 of proximity
position, depress the frame stop switch (S73)
switch (S75, right front) will pass out the
to the stops down position. This places
orange wire #290 of S75 to the white wire
12 VDC on wire #287. 12 VDC on wire #287
#290 of proximity switch (S76, right rear). If
will shift the spool of the valve and all four
the right rear frame stop is up, S76 will be
frame stops will drop down.
sensing its target. 12 VDC on the white wire
4. Depress the 20 ft. retract switch (S33) to the #290 will pass out the orange wire #289 to the
start position. This places 12 VDC on wire white wire #289 of proximity switch (S73). If
#213. 12 VDC on wire #213 will set relay the left front frame stop is up, proximity switch
(K16, pin 14). When K16 is in a set state, con- (S73) will be energized and the 12 VDC pres-
necting pins 10 to 5 and 6 to 8 of K16. 12 ent on the white wire #289 will be sent out the
VDC at pin 6 will be sent out pin 8, down wire orange wire #292 to the white wire #292 to
#252 to the valve. The attachment will begin proximity switch (S74, right rear). If the right
to retract until the frames hit the frame stops. rear frame stop is up, S74 will be sensing its
When the attachment is in the 24 ft. position, target and 12 VDC will be sent out the orange
proximity switch (S71, right side) will sense its wire #291 to pin 12 of relay (K51), resetting
target and 12 VDC on the white wire #200 will relay K51. In a reset state, pin 10 is con-
pass out the orange wire #288. 12 VDC on nected to pin 1 while pin 6 is connected to pin
the orange wire #288 will be sent to the white 4 of relay (K51). Pin 12 of K51 is jumpered to
wire #288 of proximity switch (S72, left side). pin 14 of relay (K52). 12 VDC present on wire
When S72 senses its target, 12 VDC will be #291 will energize K52. This will connect pins
sent out the orange wire #244. 12 VDC on 9 and 5 of K52. When K52 is energized, K51
wire #244 will be sent to terminal #1 of diode is effectively bypassed.
bank (DB1). 12 VDC on terminal #1 will pass
terminal #2 to pin 12 of the auto 20 relay (K16, NOTE: Either the expansion or retraction of the
pin 12). This will reset the relay, removing attachment can be stopped by depressing S32
12 VDC from wire #252. Additionally, 12 VDC (40 ft. expansion switch), S33 (20 ft. retract
at terminal #1 of DB1 is jumpered to pin 14 of switch), or S55 (auxillary 20 / 40 stop switch,
relay (K51). This will set relay (K51). In a set located in the main electrical box on the attach-
state, pins 10 and 5 and 6 and 8 will be con- ment).
nected.
Container Lights (Illustration 29-5). The contain-
5. If the attachment is in the 24 ft. position, K51 er lights, located in the cab, are used to aid the
will be set connecting pins 10 to 5 and 6 to 8. operator in the safe operation of the attachment.
12 VDC at pin 10 will pass out pin 5, down They provide the operator with a visual indication
wire #251 to the valve. It is not necessary to of interlock logic for attachment operation. The
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-7

following list describes the function of each con- to the terminal strip in the left end beam electrical
tainer light. box. Wire #236 is jumpered to wire #237 at this
1. Red Light. This light illuminates when the terminal strip. 12 VDC on the wire #237 is sent to
twistlocks are fully unlocked (additionally, the terminal #1 of diode bank (DB5). 12 VDC will
work lights on the attachment will be illumi- pass from terminal #1 to terminal #2 of DB5 to the
nated). Red container light, illuminating the light. Addi-
tionally, 12 VDC on terminal #1 of DB5 is jump-
2. Green Light. This light illuminates when the ered to terminal #5 of DB3. 12 VDC will pass from
twistlocks are fully locked. terminal #5 to terminal #6 of DB3 down wire #289
to the controller enable relay (K20, see Relay K20
3. Amber Light. This light illuminates when the
Operation). Additionally, the 12 VDC on wire
attachment is fully on the container and twist-
#237 will provide operating power to the 40-ft.
locks are in the container’s corners.
expand switch (S32) and the 20-ft. retract switch
(S33). 12 VDC on wire #237 also energizes the
work light relay (K19). K19 will energize, connect-
ing pins 5 to 3 and 6 to 4. 12 VDC at pin 5 will
pass out pin 3, down wire #242 to the left work
light (DS32), illuminating it. 12 VDC at pin 6 will
pass out pin 4, down wire #242 to the right work
light (DS33), illuminating it. Additionally, 12 VDC
at pin 4 of relay (K19) is sent down wire #263 to
the red container light mounted on the attach-
ment, illuminating the light.
Green Light Operation (Locked). The green
light operates as follows: 12 VDC is present at
both the white and red wires of proximity switch
RED LIGHT GREEN LIGHT AMBER LIGHT (S44). 12 VDC is present on the red wire of prox-
(TWISTLOCKS (TWISTLOCKS (ON-CONTAINER) imity switch (S36). The 12 VDC present on the
UNLOCKED) LOCKED) red wires is used for proximity switch coil opera-
tion only. As each of the proximity switches is tar-
Illustration 29-5. Container Lights geted, they close the internal contacts of the white
and orange wires respectively. When S44 senses
Attachment Interlock Logic For Container its target, 12 VDC is sent from the white wire #200
Lights Operation (Illustration 29-28) to the orange wire #230 to the terminal strip in the
Red Light Operation (Unlocked). Under normal right end beam electrical box. Wire #230 is jump-
operation, the red container light will be the only ered to wire #231 at this terminal strip. 12 VDC
light illuminated when approaching the container. on wire #231 is sent to the white wire #231 of
The red light operates as follows: 12 VDC is pres- proximity switch (S36). When S36 senses its tar-
ent at both the white and red wires of proximity get, the internal contacts close and the 12 VDC on
switch (S45). 12 VDC is present on the red wire the white wire #231 is sent out orange wire #232
to the terminal strip in the left end beam electrical
of proximity switch (S37). The 12 VDC present on
the red wire is used for proximity switch coil opera- box. Wire #232 is jumpered to wire #233 at this
terminal strip. 12 VDC on the wire #233 is sent to
tion only. As each of the proximity switches is tar-
geted, they close the internal contacts of the white terminal #3 of diode bank (DB5). 12 VDC will
and orange wires respectively. When S45 senses pass from terminal #3 to terminal #4 of DB5 to the
Green container light, illuminating the light. Addi-
its target, 12 VDC is sent from the white wire #200
to the orange wire #234 to the terminal strip in the tionally, 12 VDC on terminal #3 of DB5 is jump-
ered to terminal #1 of DB3. 12 VDC will pass from
right end beam electrical box. Wire #234 is jump-
ered to wire #235 at this terminal strip. 12 VDC terminal #1 to terminal #2 of DB3 down wire #289
to the controller enable relay (K20, see Relay K20
on wire #235 is sent to the white wire #235 of
proximity switch (S37). When S37 senses its tar- Operation). 12 VDC on wire #233 also energizes
the relay (K29). K29 will energize, connecting
get, the internal contacts close and the 12 VDC on
the white wire #235 is sent out orange wire #236 pins 9 and 5. 12 VDC at pin 9 will pass out pin 5,
29-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

down wire #262 to the green container light Green or Red container light is not illuminated,
mounted on the attachment, illuminating the light. 12 VDC will not be supplied to pin 86 of relay K20
and K20 will not energize unless the override
sent out the orange wire #239 to S38 on the white
wire #239. When S38 senses its target, 12 VDC Relay K59 Operation (Illustrations 22-15 and
is sent from the white wire #239 to the orange wire 29-28). Relay K59 operates as follows: 12 VDC
#240. This voltage is sent to the white wire #240 is present at pins 14 and 9 of the relay. Relay
of S41. When S41 senses its target, the internal K59 will energize when the operator occupies the
contacts close and the 12 VDC on wire #240 is seat. When the operator occupies the seat, the
sent out wire #241 to pin 14 of the twistlock inter- operator present switch (OPS) will close and pass
lock relay (K14), energizing K14. When K14 ener- ground to pin 13 of relay K59, energizing K59.
gizes, ground at pin 5 is sent out pin 9 to pin 13 of When relay K59 energizes, 12 VDC at pin 9 will
relays (K6 and K7). 12 VDC on wire #241 is sent be sent out pin 5 to the micro-switches of the joys-
to terminal #5 of diode bank (DB5). 12 VDC will tick. When the operator is not in the operator’s
pass from terminal #5 to terminal #6 of DB5 to the seat, both electrical and hydraulic operations of
Amber on-container light, illuminating the light. the joystick are suspended.
12 VDC on wire #241 is additionally sent to pin 1
on the attachment.
tion of the red or green container light will send connected to pin 14 and jumpered to diode bank
12 VDC through a bank of three diodes (DB3). (DB4) at terminal #3. The common pin 9 (wire
The diodes are used to isolate the red container #90) is connected to pin 1 (wire #241) in a de-en-
light from the green container light. From here, ergized state and in an energized state, the com-
the 12 VDC will be placed on wire #289 to pin 86 mon pin 9 is connected to pin 5 (no wire at-
of the controller enable relay (K20), energizing the tached). 12 VDC is supplied to pin 1 (wire #241)
relay provided the operator presence switch from the activation of all four on-container proximi-
(OPS) is closed. When the operator is in the seat, ty switches (S46, S49, S38, S41). When 12 VDC
the OPS switch will close and send ground to pin is present at pin 9 of relay K54, relay K58 will
85 of relay K20. When K20 energizes, 12 VDC energize. When relay K58 energizes, 12 VDC at
(supplied from CB15 to pin 30) will be sent out pin pin 9 is sent out pin 5 onto wire #90; this will ener-
87 of K20 down wire #79. This will energize the gize the lift soft landing valve. When the lift soft
controller enable solenoid valve (CDS) and allow landing valve is energized, lowering pilot pressure
pilot pressure present at port 3 to pass out port 1 (from the joystick, present at port 2 of the lift soft
of this valve, and supply pilot pressure to the joys- landing valve) is dead-headed at the lift soft land-
tick for lift / tilt hydraulic functions. When the ing valve and is not allowed to stroke the spool of
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-9
the lift valve. Pilot pressure, which supplied the replaced.
spool of the lift valve, is now vented to the hydrau-
5. If the circuit breaker maintains a set state, one
lic tank from port 1 to port 3 of the lift soft landing
valve. The spool of the lift valve (located in the lift of the output circuits is shorted. Reconnect
/ tilt valve bank) then spring returns to its neutral the wires one by one to the output side (load
state and lowering capabilities are suspended un- side) until the circuit breaker trips. Trouble-
less the override switch has been activated. shoot the circuit of the wire, that tripped the
circuit breaker, for a short.
Override Switch (Illustration 29-28). There is a
key type override switch, located on the back of 6. Isolate and remove the short from the circuit.
the control stand, that is used to bypass the inter-
lock circuitry (red, green and amber container
lights). The override switch operates as follows:
The switch must be held into the on position for
12 VDC to be present at the B terminal. When
this switch is activated, 12 VDC will be sent out
terminal S (wire #221) to the coil of relay K54.
This will energize K54 and open the circuit of the
lift soft landing solenoid, de-energizing the lift soft
landing valve. This allows lowering pilot pressure
to reach the spool of the lift valve even when the
minal #3. With the override switch activated, 12
VDC will pass from terminal #3 out terminal #4 of
diode bank DB4. Terminal #4 of DB4 is con- 5
nected to diode bank DB3, terminal #2. The out- 1
puts of DB3 are all jumped together and con-
nected to wire #289. Wire #289, in conjunction 14
with the seat belt switch (S18), control the control- 13
ler enable relay K20 (see Relay K20 Operation).
9

The override switch should
only be used while maintenancing the machine
or in an emergency.
Circuit Breakers. Circuit breakers are employed
in the electrical system and act similar to fuses,
protecting the electrical circuits and valuable com- Illustration 29-6. SP, ST 10 amp Relay
ponents from overloads which could damage
them. Perform the following troubleshooting pro- Single-Pole, Single-Throw 10 amp Relays with
cedures to troubleshoot a circuit breaker. L.E.D.s (Illustration 29-6). A relay is nothing more
1. Turn the ignition key to the “Ignition” position. than an electrically controlled switch. Relays are
always shown on electrical circuits in a de-ener-
2. If the circuit breaker is tripped, reset the circuit gized state. The positive side of the relay coil is
breaker. pin 14 while the negative side of the coil is pin 13.
3. If the circuit breaker immediately retrips, Either signal, 12 VDC or ground (or both), can be
remove all wires from the output side (load sent to the relay coil to energize the relay. A posi-
side) of the circuit breaker. tive signal is sent to relays, K8 thru K13, to ener-
gize the relay coil. Relays (K6) and (K7) require
4. Reset the circuit breaker. If the circuit breaker both positive and negative signals to be sent to
retrips, the circuit breaker is bad and must be the relay coil for the coil to be energized. Relay
29-10 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
(K6) requires a 12 VDC signal to be sent from the the relay is energized, the coil shifts the switch,
twistlock unlock micro-switch (S31) at pin 14 and connecting pins (5 and 3) and pins (6 and 4) com-
the ground be sent from the twistlock interlock pleting the circuit of both sets of pins.
relay (K14). Relay (K7) requires a 12 VDC signal
be sent from the twistlock lock micro-switch (S31)
and the ground be sent from the twistlock interlock
relay (K14). Relay (K14) will energize by one of
minals (5, 3, and 1) and terminals (6, 4, and 2). In
two ways: 12 VDC can be supplied by the twist-
a de-energized state, ensure that terminals (5 and
lock override switch (S35) to pin 14 of relay (K14)
1) and terminals (6 and 2) have continuity
or when the amber light (DS17) is illuminated, 12
between them. With an ohmmeter, check the
VDC will be supplied to relay (K14) pin 14. Relay
resistance between terminals (5 and 1) and termi-
(K17) requires two signals to be sent to the relay
nals (6 and 2). The ohmmeter should indicate a
coil in order for it to be energized.
reading of 0 - 40 ohms. Energize the relay and
When the relay is de-energized, the internal check the resistance between terminals (5 and
switch connects pins 9 and 1 completing the cir- 3)and terminals (6 and 4). The ohmmeter should
cuit of the two pins. When the relay is energized, indicate a reading of 0 - 40 ohms. If these two
the coil shifts the switch, connecting pins 9 and 5 checks are good, the relay is good. If one of
completing the circuit of the two pins. these checks fails and 12 VDC required at termi-
nal 7 was or was not present, or ground signal
properly. Do not rely on the L.E.D. to give the full
minals 9, 5, and 1. In a de-energized state,
ensure that terminals 9 and 1 have continuity
between them. With an ohmmeter, check the
resistance between terminals 9 and 1. The ohm-
meter should indicate a reading of 0 - 40 ohms.
Energize the relay and check the resistance
between terminals 9 and 5. The ohmmeter should
indicate a reading of 0 - 40 ohms. If these two
checks are good, the relay is good. If one of 3 1
these checks fails and 12 VDC required at termi- 2
nal 14 was or was not present, or ground signal at
terminal 13 was or was not present, dependant on 4
the desired state of relay (energized or de-ener- 8
gized), the relay is bad and must be replaced. 7
Double-Pole, Double-Throw 15 amp Relays

electrically controlled switch. Relays are always
shown on electrical circuits in a de-energized
state. The positive side of the relay coil is pin 7(A) 5
while the negative side of the coil is pin 8(B).
Either signal, 12 VDC or ground (or both), can be
sent to the relay coil to energize the relay.
When the relay is de-energized, the internal 6
switch connects pins (5 and 1) and pins (6 and 2)
completing the circuit of both sets of pins. When Illustration 29-7. DP, DT 15 amp Relay
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-11
at terminal 8 was or was not present, dependant ment are state-of-the-art switching devices. The
on the desired state of relay (energized or de-en- red wire of the proximity switch powers the prox-
ergized), the relay is bad and must be replaced. imity switch itself and also powers the red L.E.D.
on the cable side of the proximity switch. The
Double-Pole, Double-Throw Latching Relays
black wire is the ground side of the proximity
switch while the white wire is the common post of
electrically controlled switch. This type of relay is
the internal switch. The blue wire is the normal
shown in a reset state. A latching relay has a
closed post of the internal switch and the orange
power saving feature. It does not require the relay
wire is the normally open post of the internal
coil to be energized at all times to maintain the set
switch.
state. The positive side of the relay coil is pin 14
while the negative side of the coil is pin 13 for the The proximity switch will be energized when the
set state of the relay. The internal red flag of the proximity switch senses its target. Once this hap-
relay will be visible in the small window, located at pens, the red L.E.D. will illuminate and the internal
the top of relay’s cover, indicating a set state. In a switch will switch, closing the circuit of the white
set state, pins (10 and 5) and pins (6 and 8) of the and orange wires. The white and orange wires
relay will be closed and continuity exists between will have continuity between them only as long as
each set of pins. In a reset state, the positive side
of the relay coil is pin 12 while the negative side of
the coil is pin 9. In a reset state, pins (10 and 1)
and pins (6 and 4) of the relay will be closed and
continuity exists between each set of pins. The
internal red flag of the relay will not be visible in
the small window in the top of the relay’s cover,
indicating a reset state. A constant 12 VDC signal
is not required to set or reset the latching relay. A
momentary 12 VDC signal is required at either the
set or reset coil, depending on the desired state of
the relay, to set or reset the relay.
minals (10, 1 and 5) and (6, 8 and 4). Set the
relay by applying 12 VDC to pin 14. In a set state
(the internal red flag is visible in the window), 2
ensure that terminals (10 and 5) and (6 and 8) 5 1
have continuity between them. With an ohmme- 6
ter, check the resistance between terminals (10 4
14
and 5) and then terminals (6 and 8). The ohmme- 13
ter should indicate a reading of 0 - 40 ohms. 8
Reset the relay by applying 12 VDC to pin 12 (the
internal red flag should not be visible in the win-
dow). Check the resistance between terminals (6
and 4) and then terminals (10 and 1). The ohm-
meter should indicate a reading of 0 - 40 ohms. If
these four checks are good, the relay is good. If 9
one of these checks fails and 12 VDC required at
terminals (14 or 12) was or was not present and
ground signal at terminals (13 or 9) was pres- 10
ent,dependant on the desired state of relay (set or
reset), the relay is bad and must be replaced.
12
30mm Proximity Switches (Illustration 29-9).
The proximity switches employed on Taylor equip- Illustration 29-8. DP, DT Latching Relay
29-12 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
the proximity switch senses its target. The maxi- Single-Pole, Single-Throw, Maintain Contact
mum targeting distance is approximately 3/8”. Switches. A switch is designed with the purpose
of controlling an electrical circuit by completing or
The most effective way to troubleshoot the prox-
opening the circuit. With an ohmmeter, check the
imity switch is with an ohmmeter. This can be
resistance between the contact points of the
accomplished by disconnecting the weatherpack
switch. With the switch closed (completing the
connector (located approximately 3 foot from the
circuit), the ohmmeter reading should indicate 0 -
proximity switch), jumpering the red wires at each
40 ohms. With the switch open (opening the cir-
end and jumpering the black wires at each end.
cuit), the ohmmeter reading should be infinity. If
Target the proximity switch (the red L.E.D. should
the above checks are good, the switch is good. If
illuminate) and check the continuity of the white
any of the above checks fail, the switch is bad and
and orange wires located on the proximity switch
must be replaced.
side of the weatherpack. The ohmmeter should
indicate a reading of 0 - 40 ohms. Remove the Single-Pole, Double-Throw, Momentary Rocker
target from the proximity switch and with an ohm- Switches. This type of switch operates on the
meter, check the continuity between the white and principle that the circuit is closed only when the
orange wires. The ohmmeter should now read switch is held in the closed state. Once the switch
is released, the circuit will open. This switch is
infinity. If these two checks are good, the proximi-
checked like an On-Off switch with the exception
ty switch is good. If one of these checks fails, the
that the switch must be held closed to complete
proximity switch is bad and must be replaced. Do
resistance checks.
not rely on the red L.E.D. as a sole indicator that
the internal switch did, in fact, close. Always Solenoids. A solenoid is an electrical compo-
check the continuity between the white and nent. When electricity is applied to the coil, the
orange wires as described above. solenoid will form an electromagnet. The magnet-
ic field will pull or push an armature into the coil
(based on application). The armature can be con-
nected to a switch in electrical circuits to turn the
switch on or off. An armature can also be used to
open or close valves.
Solenoids employed as electrical switches can be
L.E.D. troubleshot with an ohmmeter. Remove the two
wires from the two larger posts of the solenoid.
Energize the solenoid. With an ohmmeter, check
the resistance between the two larger posts. The
ohmmeter should indicate between 0 - 40 ohms
nominally.
Solenoids employed as hydraulic switches are
used to open and close spools of valves. The
simplest way to prove the solenoid coil good is to
energize the solenoid and then, with a metal
object, touch the nut that secures the coil to the
cartridge. The magnetic field generated when the
coil becomes an electromagnet will be significant
enough to pull the metal object to the nut (some
solenoids employ a metal nut encased in plastic
and will require removal in order to detect the
magnetic field). This will prove the coil good; how-
RED BLUE
NC ever, the armature may be stuck. If the hydraulic
WHITE
COM. circuit is still defective at this point, remove the coil
BLACK ORANGE NO and cartridge. Now energize the coil, the arma-
ture inside the cartridge should shift. If the arma-
ture inside the cartridge did not shift and the coil is
Illustration 29-9. Proximity Switch magnetized, replace the cartridge.
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-13
Exercise care not to reverse polarity because NOTE: The targeting distance from the face of
some solenoids employ internal diodes which can each unlock proximity switch to its target must be
be destroyed when the polarity is reversed. The 1/8” - 1/4”.
solenoids employed on the transmission control
valve contain diodes. The black wire of the coil 3. Repeat procedure 2. for the left side twistlock
connects to the ground side of the circuit while the [(S37), see Illustration 29-10, View 2 of 2].
red wire goes to the positive side of the circuit. The red container light should illuminate after
the left side proximity switch (S37) is adjusted.
Diodes. Diodes are one-way conductors that pro-
vide isolation. Current flow through a diode is Lock Proximity Switches. Perform the following
from anode to cathode. They are easily proven procedures to adjust the twistlock lock proximity
good by using an ohmmeter. When using the switches for proper operation. Refer to Illustra-
ohmmeter, place the leads of the ohmmeter on tions 29-10 and 29-3 for the lock proximity
the opposite ends of the diode. Observe the ohm- switches locations.
meter reading. Then reverse the ohmmeter leads 1. Lock the twistlocks. Twistlocks should turn
on the ends of the diode. Observe the ohmmeter 90_$3_.
reading. The ohmmeter readings should indicate
a higher ohm resistance in one direction opposed NOTE: It will be necessary to use the twistlock
to the other direction because the current gener- override switch to lock the twistlocks.
ated by the ohmmeter is sufficient enough to for-
ward-bias the diode. 2. Beginning at the right side twistlock, adjust the
lock proximity switch (S44) in the clamp
Transient Suppressors. The transient suppres- towards the prox target (see Illustration 29-10,
sors protect the relays from electrical spikes which View 1 of 2) until the red L.E.D. on the rear of
could lead to early failure of the relays. If an elec- the proximity switch illuminates. After the
trical spike is detected, the transient suppressors
proximity switch L.E.D. illuminates, continue to
will conduct, completing the circuit between the
slide the proximity switch 1/8” towards the prox
protected system and ground. target before tightening the proximity switch in
Twistlocks Proximity Switches Adjustment place.
Unlock Proximity Switches. Perform the follow-
ing procedures to adjust the twistlock unlock prox- NOTE: The targeting distance from the face of
imity switches for proper operation. Refer to each lock proximity switch to its target must be
Illustrations 29-10 and 29-3 for the unlock proximi- 1/8” - 1/4”.
ty switches locations. 3. Repeat procedure 2. for the left side twistlock
1. Unlock the twistlocks. Align the twistlocks to [(S36), see Illustration 29-10, View 2 of 2].
be parallel with the guide blocks in the twistlock The green container light should illuminate
housings (unlocked position) by adjusting the after the left side proximity switch (S36) is
rod ends of the twistlock cylinder and tie rod. adjusted.
NOTE: It will be necessary to use the twistlock On-Container Proximity Switches Adjustment.
override switch to unlock the twistlocks. Perform the following procedures to adjust the on-
container proximity switches for proper operation.
2. Beginning at the right side twistlock, adjust the Refer to Illustrations 29-3 and 29-11 for the unlock
unlock proximity switch (S45) in the clamp proximity switches locations.
towards the prox target (see Illustration 29-10, 1. Raise the on-container plunger so that the
View 1 of 2) until the red L.E.D. on the rear of proximity switch may be adjusted to 1/8” - 1/4”
the proximity switch illuminates. After the from plunger collar.
proximity switch L.E.D. illuminates, continue to
slide the proximity switch 1/8” towards the prox 2. Loosen both bolts that secure the on-container
target before tightening the proximity switch in proximity switch slotted bracket to the twistlock
place. housing.
3. Position the plunger at 1/4” from the bottom of
the twistlock housing.
29-14 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
4. Slowly move the proximity switch downward 7. Activate the twistlocks lock switch (green and
towards the plunger collar until the proximity amber container lights are illuminated).
switch energizes (red L.E.D. on the backside
8. Lift the container (the amber light should go
of proximity switch is illuminated) and continue
out). If amber container light fails to go out
to lower the proximity switch an additional
when the container is lifted, repeat procedures
1/16” - 1/8” and tighten both bolts.
2. through 8.
5. Check the system by lowering the attachment
9. Set the container down (the amber container
onto an empty container.
light should illuminate). If the amber container
6. Ensure that the amber on-container light is illu- light does not illuminate, the twistlock override
minated. must be used to unlock the twistlocks from the
container (repeat procedures 2. through 9.).
TWISTLOCK
CYLINDER
FRONT RIGHT SIDE TRUCK

SIDE
LOCKED UNLOCKED
PROXIMITY PROXIMITY
SWITCH LOCKED SWITCH (S45)
UNLOCKED
TARGET PROXIMITY PROXIMITY
SWITCH (S44) SWITCH TARGET
Illustration 29-10 (View 1 of 2). Twistlock Prox Targets Sensed By Proximity Switches
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-15
TWISTLOCK
CYLINDER
TRUCK LEFT SIDE FRONT

SIDE
LOCKED UNLOCKED
PROXIMITY PROXIMITY
SWITCH LOCKED UNLOCKED SWITCH (S37)
TARGET PROXIMITY PROXIMITY
SWITCH (S36) SWITCH TARGET
Illustration 29-10 (View 2 of 2). Twistlock Prox Targets Sensed By Proximity Switches
29-16 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
1/8” - 1/4”
SLOTTED BRACKET ON-CONTAINER

PROXIMITY SWITCH
BOLT
COLLAR
PLUNGER
1/4”
BOTTOM OF
TWISTLOCK
HOUSING
Illustration 29-11. On-Container Plunger
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-17
PILE SLOPE
COUNTERBALANCE VALVE SLEW
PILE SLOPE
(If Equipped) CYLINDER
CYLINDER
(Illustration 29-30) (Illustration 29-30)
(If Equipped)
ACCUMULATOR
(Illustration 29-30) EXPANSION
FLOW DIVIDER
MAIN
VALVE
ATTACHMENT VALVE
(Illustration 29-13) SLEW CYLINDER
COUNTERBALANCE
VALVES
SIDE SHIFT
CYLINDER
SIDE SHIFT
COUNTERBALANCE
VALVES
TWISTLOCK
CYLINDER
EXPANSION (Illustration 29-30)
CYLINDERS
Illustration 29-12. Attachment Hydraulic Components
29-18 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
Attachment Hydraulics 1. Pressure Reduction Valve. The pressure
Hydraulic Components (Illustration 29-11). The reduction valve contains a pressure reducer
attachment hydraulic components consist of a which controls the maximum pilot pressure. It
main attachment valve, accumulator, counterbal- is preset to 400 psi and is non-adjustable.
ance valves, flow divider, spreader relief valve and 2. Inlet Section. The inlet section receives flow
various actuating hydraulic cylinders. from the auxiliary pump’s 2” gear set. There is
Main Attachment Valve (Illustration 29-13). The a spreader relief valve (connected to the inlet
main attachment valve is a six section 12 VDC section) that is set at 2100 psi and is located
solenoid-operated directional control valve. All on the front left side of the truck’s chassis
valve functions are controlled by on / off sole- above the drive axle. Also located on the inlet
noids. The main attachment valve is comprised of is a check valve. This valve prevents the end
the following valve sections: caps from being blown off of the work sections
should someone reverse the main hydraulic
hoses.
SET EXPANSION SECTION “A”

SET TWISTLOCK WORK SECTION PORT RELIEF VALVE TO 1000
PORT RELIEF VALVES TO 700 PSI PSI AT HIGH IDLE (EXPAND)
AT HIGH IDLE
OUTLET SECTION
PRESSURE RELIEF
VALVE (SET TO 200
PSI AT LOW IDLE)
SET EXPANSION SECTION “B”

INLET SECTION PRESSURE
PORT RELIEF VALVE TO 2000
REDUCTION VALVE
PSI AT HIGH IDLE (RETRACT)
WORK SECTION IDENTIFICATION
SS - SIDE SHIFT WORK SECTION
LS - LEFT SLEW WORK SECTION
RS - RIGHT SLEW WORK SECTION
EX - EXPANSION WORK SECTION
TL - TWISTLOCK WORK SECTION
PS - PILE SLOPE WORK SECTION (OPTIONAL)
Illustration 29-13. Main Attachment Valve
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-19
3. Side Shift Work Section. The side shift work 8. Pile Slope Work Section (if equipped). The
section, containing ports A (shift left) and B pile slope work section, containing ports A
(shift right), is connected to the side shift cylin- (right side up, left side down) and B (left side
ders by hydraulic hoses. The maximum side up, right side down), is connected to the pile
shift pressure is 2100 psi. This can be slope cylinders by hydraulic hoses. The maxi-
checked with an appropriate gauge at pres- mum pile slope pressure is 2100 psi. This can
sure check (SHC2) by fully side shifting right or be checked with an appropriate gauge at pres-
left and dead-heading the side shift cylinders. sure check (SHC2) by fully sloping right or left
and dead-heading the pile slope cylinders.
4. Left Slew Work Section. The left slew work
section, containing ports A (slew out) and B 9. Outlet Section. The outlet section provides
(slew in), is connected to the left slew cylinder the connection from the return hose back to
by hydraulic hoses. The maximum slew pres- the hydraulic tank. When no hydraulic func-
sure is 2100 psi. This can be checked with an tions are operated, the fluid flows from the
appropriate gauge at pressure check (SC2) by inlet down the center of the valves to the outlet
fully slewing out or slewing in and dead-head- and returns through the return filter. The outlet
ing the left slew cylinder. section contains a pressure relief valve set for
200 psi at low idle. This pressure relief valve
5. Right Slew Work Section. The right slew
controls the minimum pilot pressure. The out-
work section, containing ports A (slew in) and
let section also contains pressure check
B (slew out), is connected to the right slew cyl-
(SHC4). This pressure check should be used
inder by hydraulic hoses. The maximum slew
to check back pressure to the hydraulic tank.
pressure is 2100 psi. This can be checked
with an appropriate gauge at pressure check Accumulator (Illustration 29-30). There is an
(SHC2) by fully slewing in or slewing out and accumulator connected to the outlet section of the
dead-heading the right slew cylinder. main attachment valve and is precharged at 65
psi (4.5 bar). It functions as a shock absorber in
6. Expansion Work Section. The expansion
the attachment hydraulic circuit. Refer to Section
work section, containing ports A (expand) and
22E for procedures for checking the precharge
B (retract), is connected to the expansion cyl-
and charging the accumulator.
inders by hydraulic hoses. The A port con-
tains a port relief valve that limits the maximum Counterbalance Valves (Illustration 29-31). The
expand pressure to 1000 psi while the B port counterbalance valves are used in the attachment
contains a port relief valve that limits the maxi- hydraulic circuit to counterbalance the weight that
mum retract pressure to 2000 psi. This can be is supported by some of the cylinders. They keep
checked with an appropriate gauge at pres- the cylinders from running-away due to heavy
sure check (SHC2) by fully extending or loads.
retracting and dead-heading the expansion Flow Divider Valve (Illustration 29-31). A flow
cylinders. divider valve receives one input flow and divides it
7. Twistlock Work Section. The twistlock work into two approximately, equal separate flows.
section, containing ports A (lock twistlocks) Spreader Relief Valve (Illustration 29-31). The
and B (unlock twistlocks), is connected to the spreader relief valve controls the maximum pres-
twistlock cylinders by hydraulic hoses. The A sure that can be developed by any of the six work
and B ports contains port relief valve that limit sections of the main attachment valve. It is con-
the maximum lock and unlock pressures to nected to the inlet section of the main attachment
700 psi. These pressures can be checked valve and is set at 2100 psi. The spreader relief
with an appropriate gauge at pressure check valve is located on the front left side of the truck’s
(SHC2) by fully locking or unlocking and dead- chassis above the drive axle.
heading the twistlock cylinders. Both port
relief valves of this work section are
non-adjustable.
29-20 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
OUT
4. Loosen the locknut on the spreader relief
valve (see Illustration 29-15).
PRESSURE
CHECK 5. With a hex wrench, turn setscrew clockwise to
(SHC1) increase the pressure or counterclockwise to
decrease the pressure.
been set.
Expansion Section A Port Relief Valve (Illustra-
tion 29-13). Perform the following procedures to
set the expansion section A port relief valve pres-
sure.
IN 1. Remove and plug (13/16” plug) the hydraulic
hoses from the expansion work section. Then
cap (13/16” cap) the ports of the expansion
work section.
RELIEF 2. Install a 3000 psi pressure gauge into pres-
sure check (SHC2, Illustration 29-31).
Illustration 29-14. Spreader Relief Valve
3. Install a jumper wire at terminal #200 in the
Setting Hydraulic Pressures attachment junction box. The jumper wire
must be long enough to reach the solenoid of
the expansion work section.

4. With the jumper wire, touch the post of the
S Under no circumstances, when setting pres- solenoid on the A port of the expansion work
sures, allow any portion of your body to be section. This procedure will override the
positioned in front of the relief. It is possible double-latching relay (K15), allowing the
that the relief could be blown loose with expansion cylinder to be dead-headed
great force which could cause severe bodily (extend).
injury or death.
S Fluid passing over a relief generates heat; of the A port relief valve for 1000 psi. Refer to
should a relief be blown loose, hot, pressur- procedures 6. through 8. to set the pressure.
ized fluid will be forced from the open port.
This could cause severe bodily injury. 6. Loosen the locknut on the A port relief valve
S When setting hydraulic pressures, be aware (see Illustration 29-13).
of what could happen should cylinder col- 7. Turn the setscrew clockwise to increase the
lapse or go full stroke uncontrollably. This pressure or counterclockwise to decrease the
could lead to severe personal injury or pressure.
death.
Spreader Relief Valve (Illustration 29-14). Per- been set.
form the following procedures to set the system
Expansion Section B Port Relief Valve (Illustra-
pressure on the spreader relief valve.
tion 29-13). Perform the following procedures to
1. Install a 3000 psi pressure gauge into pres- set the expansion section B port relief valve pres-
sure check (SHC1, Illustration 29-31). sure.
2. Fully slew the attachment out (or in) and dead- 1. Remove and plug (13/16” plug) the hydraulic
head the slew cylinder. hoses from the expansion work section. Then
cap (13/16” cap) the ports of the expansion
work section.
for 2100 psi. Refer to procedures 4. through
6. to set the pressure. 2. Install a 3000 psi pressure gauge into pres-
sure check (SHC2, Illustration 29-31).
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-21
3. Install a jumper wire at terminal #200 in the
attachment junction box. The jumper wire
must be long enough to reach the solenoid of
4. With the jumper wire, touch the post of the
solenoid on the B port of the expansion work
section. This procedure will override the
double-latching relay (K16), allowing the
expansion cylinder to be dead-headed
(retract).
of the B port relief valve for 2000 psi. Refer to
procedures 6. through 8. to set the pressure.
6. Loosen the locknut on the B port relief valve
(see Illustration 29-13).
pressure.
been set.
Main Attachment Pilot Pressure Relief Valve
(Illustration 29-13). Perform the following proce-
dures to set the pilot pressure relief valve of the
main attachment valve.
1. Install an pressure gauge into pressure check
(SHC2, Illustration 29-31).
for 200 psi. Refer to procedures 3. through 5.
to set the pressure.
3. Loosen the locknut on the pilot relief valve
located in the outlet section (see Illustration
29-13).
pressure.
5. Tighten the locknut after the pilot pressure has
been set.
29-22 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
Container Attachment Troubleshooting
(Illustrations 29-28 and 29-29)
Some of the components described in this trouble-
shooting chart are optional equipment.
1. Red light will not illu- 1. Twistlocks are not fully unlocked. 1. Fully unlock the twistlocks.
minate (twistlocks
2. Bulb is blown. 2. All three container light bulbs can
did rotate)
be checked by depressing the
switch (S53) located on the right
side of the container lights base.
Replace blown bulb.
3. One of the proximity switches 3. Fully unlock twistlocks and adjust
(S45 or S37) is not sensing its proximity switch at fault to sense
target. its target. With the twistlocks fully
unlocked, the red L.E.D. (in the
back of the proximity switches)
should be illuminated, indicating
that the proximity switches are
sensing their targets.
4. One of the proximity switches 4. If the red L.E.D. is illuminated, this
(S45 or S37) is defective. indicates that the proximity
switch’s coil did energize. It does
not indicate that the contact points
of the white and orange wires
closed. With the red L.E.D. illumi-
nated, check the continuity of the
white and orange wires with an
ohmmeter. The ohmmeter should
indicate between 0 - 40 ohms. If
ohmmeter reading indicates infin-
ity and the red L.E.D. is illumi-
nated, replace proximity switch.
5. Loose, open or shorted wire(s). 5. Isolate and repair wire(s).
6. Transient suppressor on wire #237 6. Replace transient suppressor on
is shorted. wire #237.
7. Defective diode between terminals 7. Replace diode bank (DB5).
#1 and #2 of diode bank (DB5).
2. Red light will not illu- 1. Defective relay (K6). 1. Replace defective relay (K6).
minate (twistlocks Refer to Single-Pole, Single-
did not rotate, over- Throw 10 amp Relays with
ride switch was acti- L.E.D.s in the Component Trou-
vated) bleshooting.
2. Defective twistlock unlock micro 2. Replace defective micro switch
switch (S31). (S31).
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-23
2. Red light will not illu- 3. .3 amp circuit breaker (CB17) is 3. Replace or reset circuit breaker
minate (twistlocks defective or tripped. (CB17).
did not rotate, over-
ride switch was acti-
vated) 5. Loose connection or pin broken at 5. Isolate and repair.
(Continued) electrical connector.
6. Defective relay (K14). 6. Replace defective relay (K14).
Refer to Single-Pole, Single-
Throw 10 amp Relays with
L.E.D.s in the Component Trou-
bleshooting.
7. 10 amp circuit breaker (CB19) is 7. Replace or reset circuit breaker
defective or tripped. (CB19).
8. Defective solenoid on the B port of 8. Refer to Solenoids in the Compo-
the twistlock work section. nent Troubleshooting to trouble-
shoot. Replace defective sole-
noid.
9. Defective B port pilot cartridge on 9. Replace B port pilot cartridge.
the twistlock work section.
10. Defective twistlock work section. 10. Replace or repair twistlock work
section.
11. Defective B port relief valve in the 11. Replace B port relief valve.
twistlock work section.
12. Low or no pilot pressure. 12. Adjust pilot pressure.
3. No container attach- 1. 15 amp circuit breaker (CB20) is 1. Replace or reset circuit breaker
ment lights will illu- defective or tripped. (CB20).
minate
4. Amber light will not 1. Bulb is blown. 1. All three container light bulbs can
illuminate be checked by depressing the
Replace blown bulb.
3. One of the proximity switches 3. Adjust the proximity switch at fault
(S46, S49, S38 and S41) is not to sense its target.
sensing its target.
continued
29-24 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
4. Amber light will not 5. One of the proximity switches 5. If the red L.E.D. is illuminated, this
illuminate (S46, S49, S38 and S41) is defec- indicates that the proximity
(Continued) tive. switch’s coil did energize. It does
6. Loose, broken or shorted wire. 6. Isolate and repair wire.
7. Damaged container corner. 7. Report damaged container to the
proper authority.
5. Amber light will not 1. Loose, broken or shorted wire. 1. Isolate and repair wire.
illuminate (twistlock
override switch was
activated)
5. Defective override switch (S35). 5. Replace override switch (S35).
Replace blown bulb.
6. Green light will not 1. Twistlocks are not fully locked. 1. Fully lock the twistlocks.
illuminate (twistlocks
did rotate)
Replace blown bulb.
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-25
6. Green light will not 4. One of the proximity switches 4. Fully lock twistlocks and adjust
illuminate (twistlocks (S44 or S36) is not sensing its proximity switch at fault to sense
did rotate) target. its target. With the twistlocks fully
(Continued) locked, the red L.E.D. (in the back
of the proximity switches) should
be illuminated, indicating that the
proximity switches are sensing
their targets.
(S44 or S36) is defective. indicates that the proximity
switch’s coil did energize. It does
7. Green light will not 1. Defective relay (K7). 1. Replace defective relay (K7).
illuminate (twistlocks Refer to Single-Pole, Single-
vated) bleshooting.
2. Defective twistlock lock micro 2. Replace defective unlock micro
4. .3 amp circuit breaker (CB17) is 4. Replace or reset circuit breaker
bleshooting.
continued
29-26 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
7. Green light will not 7. 10 amp circuit breaker (CB19) is 7. Replace or reset circuit breaker
illuminate (twistlocks defective or tripped. (CB19).
8. Defective solenoid on the A port of 8. Refer to Solenoids in the Compo-
vated) the twistlock work section. nent Troubleshooting to trouble-
(Continued) shoot. Replace defective sole-
noid.
9. Defective A port pilot cartridge on 9. Replace A port pilot cartridge.
section.
11. Defective A port relief valve in the 11. Replace A port relief valve.
8. No or slow 40 FT. 1. Red light is not illuminated. 1. Refer to Problems 1. and 2. (with
expansion the exception of the bulb being
blown) in this troubleshooting
chart.
2. Defective 40 ft. expand switch 2. Replace 40 ft. expand switch
(S32). (S32).
4. Defective double-latching relay 4. Refer to Double-Pole, Double-
(K15). Throw Latching Relays in the
found earlier in this section.
Replace if required.
7. Mis-adjusted A port relief valve in 7. Adjust A port relief valve and set
the expansion work section. to 1000 psi.
expansion work section.
the expansion work section. nent Troubleshooting to trouble-
noid.
11. Defective expansion work section. 11. Replace or repair expansion work
section.
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-27
8. No or slow 40 FT. 12. Defective flow divider valve (FDV). 12. Replace flow divider valve (FDV).
expansion
13. One of the expansion cylinders 13. Isolate and repack expansion cyl-
(Continued)
packing is defective. inder. To isolate the defective cyl-
inder, perform the following:
a. With the attachment is in the
20 ft. position, remove the
hydraulic hoses from the pis-
ton ends of both expansion
cylinders and plug them.
b. In the attachment main junc-
tion box, install a jumper wire
at terminal #200 and start the
truck.
c. Touch the jumper wire to the B
port solenoid post of the
expansion work section. This
will direct the main flow of
hydraulic fluid to the rod end of
the expansion cylinders.
d. Observe the open ports on the
piston end of the expansion
cylinders. If a flow of fluid is
retract the exception of the bulb being
chart.
2. Defective 20 ft. retract switch 2. Replace 20 ft. retract switch (S33).
(S33).
7. Mis-adjusted B port relief valve in 7. Adjust B port relief valve and set
continued
29-28 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
9. No or slow 20 FT. 8. Defective solenoid on the B port of 8. Refer to Solenoids in the Compo-
retract (Continued) the expansion work section. nent Troubleshooting to trouble-
noid.
section.
11. Defective flow divider valve (FDV). 11. Replace flow divider valve (FDV).
12. One of the expansion cylinders 12. Refer to Correction 13. of Problem
packing is defective. 8. in this troubleshooting chart.
10. No or slow side shift 1. Defective side shift micro switch 1. Replace side shift micro switch
(left) (S30). (S30).
2. Defective relay (K8). 2. Replace relay (K8).
the side shift work section. nent Troubleshooting to trouble-
noid.
the side shift work section.
7. Defective side shift work section. 7. Replace or repair side shift work
section.
9. One of the side shift cylinders 9. Isolate and repack side shift cylin-
packing is defective. der. To isolate the defective cylin-
a. With the attachment fully side
shifted to the right, remove the
ton ends of both side shift cyl-
inders and plug them.
b. Depress the right side shift
micro switch (S30) on the joys-
tick.
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-29
10. No or slow side shift c. Observe the open ports on the

(left) (Continued) piston end of the side shift cyl-
inders. If a flow of fluid is
(right) (S30). (S30).
noid.
section.
8. One of the side shift cylinders 8. Refer to Correction 8. of Problem
12. No or slow slew left 1. Defective left slew micro switch 1. Replace left slew micro switch
(out) (S28). (S28).
the left slew work section. nent Troubleshooting to trouble-
noid.
the left slew work section.
7. Defective left slew work section. 7. Replace or reset circuit breaker
(CB17).
continued
29-30 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
12. No or slow slew left 8. .3 amp circuit breaker (CB17) is 8. To check the left slew cylinder,
(out) (Continued) defective or tripped. perform the following:
9. The left slew cylinder packing is a. With the attachment fully
defective. slewed out (left side), remove
the hydraulic hoses from the
rod end of the left slew cylin-
der and plug.
b. Depress the left slew out micro
switch.
c. Observe the open port on the
der. If a flow of fluid is
detected from the cylinder,
repack the cylinder.
(in) (S28). (S28).
noid.
7. Defective left slew work section. 7. Replace or repair left slew work
section.
8. The left slew cylinder packing is 8. Refer to Correction 8. of Problem
defective. 12. in this troubleshooting chart.
14. No or slow slew 1. Defective right slew micro switch 1. Replace right slew micro switch
right (out) (S29). (S29).
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-31
14. No or slow slew 5. Defective solenoid on the A port of 5. Refer to Solenoids in the Compo-
right (out) the right slew work section. nent Troubleshooting to trouble-
noid.
the right slew work section.
7. Defective right slew work section. 7. Replace or repair right slew work
section.
9. The right slew cylinder packing is 9. To check the right slew cylinder,
defective. perform the following:
a. With the attachment fully
slewed out (right side), remove
rod end of the right slew cylin-
der and plug.
b. Depress the right slew out
tick.
right (in) (S29). (S29).
the right slew work section. nent Troubleshooting to trouble-
noid.
section.
8. The right slew cylinder packing is 8. Refer to Correction 8. of Problem
continued
29-32 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
15. No or slow slew 9. .3 amp circuit breaker (CB17) is 9. Replace or reset circuit breaker
right (in) defective or tripped. (CB17).
(Continued)
16. No or slow pile 1. Defective pile slope rocker switch 1. Replace pile slope rocker switch
slope right (if (S34). (S34).
equipped with pile
slope)
the pile slope work section. nent Troubleshooting to trouble-
noid.
the pile slope work section.
7. Defective pile slope work section. 7. Replace or repair slew work
section.
8. The pile slope cylinder packing is 8. To check the pile slope cylinder,
a. With the attachment fully pile
sloped left (the right pile slope
cylinders are fully extended
while the left pile slope cylin-
ders are fully retracted).
b. Slowly remove the hydraulic
hoses from the piston ends of
the left pile slope cylinders to
allow any trapped hydraulic
pressure to bleed off. Remove
rod ends of the right pile slope
cylinders. Plug all four hydrau-
lic hoses.
c. Depress the pile slope left
switch (S34) on the control
stand.
d. Observe the open ports of the
pile slope cylinders. If a flow
of fluid is detected from any
cylinder, repack that defective
cylinder.
continued
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-33
16. No or slow pile 9. Defective counterbalance valve 9. Replace counterbalance valve

slope right (if cartridge. cartridge.
equipped with pile
10. Defective counterbalance valve. 10. Replace counterbalance valve.
slope)
(Continued)
slope left (if (S34). (S34).
equipped with pile
slope)
noid.
7. Defective pile slope work section. 7. Replace or repair right slew work
section.
sloped right (the right pile
slope cylinders are fully
retracted while the left pile
extended).
the right pile slope cylinders to
rod ends of the left pile slope
lic hoses.
c. Depress the pile slope right
stand.
continued
29-34 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
17. No or slow pile d. Observe the open ports of the

slope left (if pile slope cylinders. If a flow
equipped with pile of fluid is detected from any
slope) cylinder, repack that defective
(Continued) cylinder.
9. Defective counterbalance valve 9. Replace counterbalance valve
18. Twistlocks drift 1. The twistlock cylinder packing is 1. Isolate and repack twistlock cylin-
defective. der. To isolate the defective cylin-
a. With the twistlocks fully
unlocked, remove the front cap
(located on the top side of the
twistlock cylinder) of the left
twistlock cylinder and the rear
cap of the right twistlock cylin-
der (located on the top side of
the twistlock cylinder).
b. Turn the twistlock override
switch on and depress the
unlock twistlocks micro switch
(S31) on the joystick.
left and right twistlock cylinder.
If a flow of fluid is detected
from either of the cylinders,
this is the bad cylinder and
requires repacking.
2. Defective twistlock work section. 2. Repair or replace twistlock work
section.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-35
Container Attachment Structure. The container shim the expansion frames. Refer to Illustration
attachment is a top lift attachment that is con- 29-15 for the location of the inner and outer sup-
structed of high-strength steel. The container ports.
attachment is carefully engineered and ruggedly
1. Ensure that the weight of the expansion
constructed, although welded steel structures
frames is resting on the wear pads and the
always contain undetectable cracks, especially
attachment is extended to the 40 FT. position.
welded joints. When these joints are subject to
fluctuating stresses of significant magnitude,
these cracks will grow. This is known as fatigue

crack growth. No matter how low the stress levels S Do not climb on the mast, on top of the cab,
are kept, some fatigue crack growth will occur in or on other high places of the container han-
all welded structures. Refer to SIRR in the dling truck while performing maintenance.
Appendices for structural inspection of the
attachment assembly. S Always use OSHA approved ladders, stands
or manlifts to reach high places on the truck.
Maintenance / Inspections. There are several
inspectional requirements which must be per- S Do not remove the bolts (1, Illustrations
formed daily. These inspections must include 29-16 and 29-17) from any of the inner or out-
checking all welds and structural members for er supports when adding or removing shims.
cracks. Check all mast mounting hardware and lift Only loosen the bolts to insert or remove
chains for damage or loose bolts. Hydraulic shims.
hoses and fittings must be checked for leaks and S If shimming is required, support the weight
signs of wear or damage. of the expansion frames before adding ANY
shims when the attachment is in the 20 FT.
or 40 FT. position. Never loosen bolts (1)

without supporting the expansion frames.
S Do not climb on the mast, on top of the cab,
or on other high places of the container han- NOTES:
dling truck while performing maintenance. S Replace any inner wear pads (6) that have
S Always use OSHA approved ladders, stands become cracked, damaged, or worn to 9/16”
or manlifts to reach high places on the truck. thickness. If a 1/16” gauge can be inserted
S Never ride on the platform of the truck. between the expansion frame top plate (9) and
the bottom of the inner support while the
S Do not use a container handling truck as a attachment is in the 40 FT. position, the inner
means to elevate personnel. wear pad (6) still has wear life and does not
Expansion Frame Wear Pads have to be replaced.
1. Inner Wear Pads (Illustration 29-15). The S Replace any bottom slide pads (7) that have
inner wear pads (6) should be checked month- become cracked, damaged, or worn to 3/8”
ly or every 250 hours, whichever comes first. thickness.
Replace any inner wear pads that become 2. Refer to Illustration 29-17 and measure the ”D”
cracked, damaged, or worn to 9/16” thickness. clearance. This measurement is to be main-
The inner wear pads are located on the four tained at 1/8” at the inner supports only.
inner support locations (see Illustration 29-15).
a. To install new inner wear pads (6), remove
2. Bottom Slide Pads (Illustration 29-15). The the slide pad keeper (4) and slide pad keep-
bottom slide pads (7) should be checked er bar (8) from the inner support. Loosen
monthly or every 250 hours, whichever comes bolts (1) and remove the worn inner wear
first. Replace any bottom slide pads that pad (6) and replace with a new wear pad.
become cracked, damaged, or worn to 3/8” Ensure that the ”B” and ”C” clearances have
thickness. There are two bottom slide pads been maintained to 1/16” before tightening
located on every inner and outer support. the bolts (1). Tighten bolts (1) to a torque
Expansion Frame Shimming (Illustrations 29-16 value of 1350 - 1500 ft-lbs.
and 29-17). Perform the following procedures to
29-36 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
1. BOLT
2. SLIDE PAD PLATE
EXPANSION FRAME 3. SHIMS (12 GA.,16 GA., 5/16”)
4. SLIDE PAD KEEPER
OUTER SUPPORTS
5. NUT
6. INNER WEAR PAD
7. BOTTOM SLIDE PAD
8. SLIDE PAD KEEPER BAR
9. EXPANSION FRAME TOP
EXPANSION FRAME PLATE
INNER SUPPORTS 10. SLIDE CAP PLATE
REAR
(TRUCK SIDE)
EXPANSION FRAME
RIGHT OUTER SUPPORTS
FRONT
5
9
LEFT
2 7 6
8
1 4
10
COMMON TO EXPANSION FRAME INNER & COMMON TO EXPANSION FRAME INNER

OUTER SUPPORTS. SUPPORTS ONLY.
Illustration 29-15. Expansion Frame Inner and Outer Support Locations
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-37
EXPANSION FRAME SUPPORTS
20 FT. ATTACHMENT POSITION
1. BOLT
2. SLIDE PAD PLATE
3. SHIMS (12 GA.,16 GA., 5/16”)
4. SLIDE PAD KEEPER
5. NUT
6. INNER WEAR PAD
7. BOTTOM SLIDE PAD
PLATE
10. SLIDE CAP PLATE
INNER SUPPORT OUTER SUPPORT

5 5
6
8
4
3
3
9
2 2
7 1 7 1
10 10
EXPANSION EXPANSION
FRAME’S FRAME’S
VERTICAL VERTICAL
PLATE PLATE
Illustration 29-16. Expansion Frame Supports
29-38 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
EXPANSION FRAME SUPPORTS
40 FOOT ATTACHMENT POSITION
1. BOLT
2. SLIDE PAD PLATE
3. SHIMS (12 GA.,16 GA., 5/16”)
4. SLIDE PAD KEEPER
5. NUT
6. INNER WEAR PAD
7. BOTTOM SLIDE PAD
PLATE
10. SLIDE CAP PLATE
INNER SUPPORT OUTER SUPPORT

5 5
6 7 1/8” 7
8
1/8” CLEARANCE
CLEARANCE
4
3
3
9 ”A”
”D” 2
2
10 1 10 1
1/16” CLEARANCE ”B” 1/16” CLEARANCE ”B”
”C” 1/16” CLEARANCE ”C” 1/16” CLEARANCE
EXPANSION EXPANSION
FRAME’S FRAME’S
VERTICAL VERTICAL
PLATE PLATE
Illustration 29-17. Expansion Frame Supports

b. To remove the bottom slide pads (7), c. The ”D” clearance is to be maintained at
remove the slide cap plates (10) from the 1/8” by adding or removing shims (3), or by
slide pad plate (2). Remove the worn bot- the replacement of the bottom slide pads
tom slide pads (7) and replace with new (7).
slide pads.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-39
d. To add or remove shims (3), the bolts (1) slide pad (7) and the expansion frame vertical
must be loosened. plate. Tighten bolts (1) to a torque value of
1350-1500 ft-lbs.
NOTE: If shimming is required, add or remove
shims (3) of equal size to both sides of the expan- 5. Raise the attachment off the supports. Then,
sion frame. retract and extend the expansion frames sev-
eral times.
e. When the ”D” clearance is adjusted, ensure 6. Extend the attachment to the 40 FT. position
that the ”B” and ”C” clearances have been and recheck the clearances ”A”, ”B”, ”C”, and
maintained to 1/16” (see procedure 4.). If ”D” stated in the procedures above to ensure
bolts (1) are loosened, tighten bolts to a that the specified clearances have been
torque value of 1350 - 1500 ft-lbs. achieved.
NOTE: Replace any bottom slide pads (7) that Carriage Slider Beam Wear Pads (Illustration
have become cracked, damaged, or worn to 3/8” 29-18). The carriage slider beam wear pads must
thickness. be replaced when they become cracked, damaged
or worn to 5/8” thickness.
3. Refer to Illustration 29-17 and measure the ”A” Carriage Main Rollers (Illustration 29-18). The
clearance. This measurement is to be main- main rollers of the carriage employ greaseable,
tained at 1/8” at the outer supports only. shielded, tapered roller bearings for increased
a. To remove the bottom slide pads (7), durability. The carriage main rollers must be
remove the slide cap plates (10) from the greased monthly or every 250 hours, whichever
slide pad plate (2). Remove the worn bot- comes first. The carriage main rollers should be
tom slide pads (7) and replace with new inspected for flat spots or evidence of sliding any
slide pads. time the carriage is removed from the inner mast.
b. The ”A” clearance is to be maintained at
1/8” by adding or removing shims (3), or by The roller assemblies must not
the replacement of the bottom slide pads be over lubricated. Excess grease inside the
(7). mast rails may cause the rollers to slide when
c. To add or remove shims (3), the bolts (1) subjected to a heavy load. If this happens, a flat
must be loosened. spot will be worn on the rollers and the rollers
will continue to slide until replaced with new
NOTE: If shimming is required, add or remove rollers.
shims (3) of equal size to both sides of the expan-
sion frame. Lubrication. Refer to the Lubrication section in
the Appendices for information on lubricating the
d. When the ”A” clearance is adjusted, ensure attachment.
that the ”B” and ”C” clearances have been
maintained to 1/16” (see procedure 4.). If
bolts (1) are loosened, tighten bolts to a
torque value of 1350 - 1500 ft-lbs.
NOTE: Replace any bottom slide pads (7) that
have become cracked, damaged, or worn to 3/8”
thickness.
4. These measurements are to be maintained at
1/16”. If the ”B” or ”C” clearance is not 1/16”
on each side of the expansion frame vertical
plate, replace the bottom slide pads (7), or
loosen bolts (1) and adjust (slide in or out) the
slide pad plates (2) until the ”B” and ”C” clear-
ances measures 1/16” between the bottom
29-40 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
SLIDER BEAM
WEAR PADS
MAIN
ROLLERS
Illustration 29-18. Carriage
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-41

Illustration 29-19. Main Attachment Junction Box
06A-2458 SHT. 05
29-42 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
Illustration 29-20. Attachment Left End Junction Box
06A-2458 SHT. 06
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-43
Illustration 29-21. Attachment Right End Junction Box
06A-2458 SHT. 07
29-44 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
Illustration 29-22. Attachment Hydraulic Supply Circuit
BULKHEAD
PLATE
SUPPLY FLOW
FROM AUXILIARY
PUMP
RETURN TO
HYDRAULIC
RESERVOIR
22A-3518 SHT. 02
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-45
Illustration 29-23. Side Shift Hydraulic ANSI Circuit
22A-3518 SHT. 04
29-46 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
Illustration 29-24. Left Slew and Right Slew Hydraulic ANSI Circuit
22A-3518 SHT. 05
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-47
Hoist Circuit
29-48 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 29-25. Expansion Hydraulic ANSI Circuit
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-49
29-50 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
22A-3518 SHT. 06
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-51
Hoist Circuit
29-52 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 29-26. Twistlock Hydraulic ANSI Circuit
22A-3518 SHT. 07
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.03/04)
06/03) 29-53
Illustration 29-27. Pile Slope Hydraulic ANSI Circuit
22A-3518 SHT. 08
29-54 THDC
THDC/ /THDCP
THDCP--954
954/ /955
955/ /974
974/ /975
975(Rev.
(Rev.06/03)
03/04)
Hoist Circuit

FOLDER ENVELOPES:
Illustration 29-28 - 06A2458 SHT. 10 (ANSI)
Illustration 29-29 - 06A2458 SHT. 11 (Attachment
Control ANSI Circuit)
Illustration 29-30 - 22A3518 SHT. 1 (Shop)
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.3/05)
06/03) 29-55
Container Attachment (Twistlocks and Pin System)
Introduction. This section contains electrical, tion. The solenoid on the B port side will form an
hydraulic, and mechanical operational information electro-magnet when energized. This shifts the
for the optional pin system attachment. pilot spool cartridge, allowing pilot pressure to shift
the main spool of the work section. This will divert
Pin Mode Operation (Illustration 29-60) system hydraulic oil to the drive motor. The car-
This section explains the electrical operation of riage assemblies will be moved outward. The car-
the pin mode. riage assemblies will extend until the expansion
carriage out proximity switches sense their tar-
Depressing the mode select switch to select the gets. The right hand side of the attachment op-
pin mode, will send 12 VDC from the mode select erates as follows: 12 VDC is present at red wire
switch down wire #286 to the coil of the pin mode of proximity switch (S67). Ground is present on
relay (K47, pin 14) energizing the relay. When the orange wire #211. The 12 VDC present on
K47 energizes, 12 VDC at the common pin #9 is the red wire is used for proximity switch operation
sent out pin #5 to the coil of the interlock relay only. When the proximity switch is targeted, it will
(K14, pin #14), energizing K14. When K14 ener- close the internal contacts of the white and orange
gizes, ground, present at pin #5, is sent out the wires. When S67 senses its target, ground is sent
common pin #9 to the coils of the unlock and lock from the orange wire #211 to the white wire #264.
relays (K6 and K7, pin #13). Neither K6 nor K7 This ground is sent to the coil of the right beam
will energize until 12 VDC is placed on pin #14 of extended relay (K38, pin 13). This energizes K13.
their coils. Additionally, 12 VDC on wire #286 is Pins (12 and 8) of relay K38 will close and pins (9
sent to the coil of the pin mode relay (K33, pin 14) and 1) will open. This removes 12 VDC from the
energizing K33. When K33 energizes, 12 VDC at SPVR valve and stops the flow of hydraulic oil to
common pin #9 is sent out pin #5 on #281, ener- the motor.
gizing the blue lights (PIN MODE). Additionally,
12 VDC on wire #286 is sent to the coil of the Depressing the Clamp / Unclamp micro switch to
valve select relay (K42, pin #14) energizing the the Clamp position will send 12 VDC down wire
relay. K42, in an energized state, will send electri- #203 to the coil of the Lock relay (K7, pin 14).
cal control signals to the Clamp work section This will energize K14 provided the ground from
instead of the twistlock work section. the interlock relay (K14, pin 9) is present on pin
#13 of the coil of relay K7. When K7 energizes,
Depressing the Clamp / Unclamp micro switch to 12 VDC at the common pin #9 is sent out pin 5
the Unclamp position will send 12 VDC down wire down wire #223 to pin 9 of the valve select relay
#202 to the coil of the Unlock relay (K6, pin 14). (K42). K42 will be energized in the pin mode. In
This will energize K6, provided the ground from an energized state, pin 9 is connected to pin 5 of
the interlock relay (K14, pin 9) is present on pin K42. 12 VDC on pin 9 is sent out pin 5 down wire
#13 of the coil of relay K6. When K6 energizes, #256 to the solenoid on the A port side of the
12 VDC at the common pin #9 is sent out pin #5, clamp work section. The solenoid on the A port
down wire #222 to the coil of the unlock relay side will from an electro-magnet when energized.
(K49, pin 14). K49 will energize and send 12 VDC This shifts the pilot spool cartridge, allowing pilot
from pin #9 out pin #5 down wire #282 to the pressure to shift the main spool of the work sec-
unlock interlock relay (K48, pin 5). K48 will ener- tion. This will divert system hydraulic oil to the
gize when the amber on container light is illumi- drive motor. The carriage assemblies will be
nated. When K48 energizes, 12 VDC present at moved inward. The carriage assemblies will come
pin #5 will be sent out pin #9, down wire #282 to in until they contact the stop plate when not on a
the reset coil of the clamp pressure achieve relay container. When clamping to a container, the
(K41). This will reset K41 and open the contacts clamp proximity switches (S65, S70, S59, and
of pins 10 and 5, removing the 12 VDC from the S63) will sense the container and energize. The
Green container light (clamp). Additionally, the proximity switches are paired together and in
unlock interlock relay (K50) will de-energize. series; each set controlling a relay. The right
12 VDC on wire #282 is sent to pin #12 of the hand side of the attachment operates as fol-
valve select relay (K42). K42 is energized while in lows: 12 VDC is present at both the white and
the pin mode of operation. 12 VDC present at pin red wires of proximity switch (S65). 12 VDC is
#12 is sent out on pin #8, down wire #255 to the present on the red wire only of proximity switch
solenoid on the B port side of the clamp work sec- (S70). The 12 VDC present on the red wire is
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-57

used for proximity switch operation only. As each extended relay (K37, pin 13). This energizes K37.
of the proximity switches is targeted, they close Pins (12 and 8) will close and pins (9 and 1) will
the internal contacts of the white and orange wires open. This removes 12 VDC from the SPVL valve
respectively. When S65 senses its target, 12 VDC and stop the flow of hydraulic oil to the motor.
is sent from the white wire #200 to the orange wire 12 VDC present at pin 12 is sent out pin 8 to pin
#260. This voltage is sent to the white wire #260 12 of the right beam extended relay (K38). K38
of S70. When S70 senses its target, the internal energized when the right carriages extended.
contacts close and the 12 VDC on wire #260 is 12 VDC present at pin 12 of K38 is sent out pin 8,
sent out orange wire #261 to coil of the right side down wire number #263A to pin 9 of the wide
pins locked relay (K40, pin 14), energizing K40. twistlock relay (K46). K46 is de-energized in the
This connects pins 9 and 5 of relay K40. The Left pin mode of operation. 12 VDC, present at pin 9,
hand side of the attachment operates as fol- is sent out pin 1, down wire #263B and wire #237
lows: 12 VDC is present at both the white and to the coil of the work light relay (K19, pin 7), ener-
red wires of proximity switch S59. 12 VDC is gizing relay K19. 12 VDC present at pins (5 and
present on the red wire only of proximity switch 6) is sent out pins 3 and 4 respectively, down wire
(S63). The 12 VDC present on the red wire is #242, illuminating the twistlock work lights and the
used for proximity switch operation only. As each red unclamp container lights.
of the proximity switches is targeted, they close
the internal contacts of the white and orange wires
switch S66. 12 VDC is present on the red wire
only of proximity switches (S69, S60, and S62).
proximity switch operation only. As each of the
sent out orange wire #277 to the coil of the left
proximity switches is targeted, they close the inter-
side pins locked relay (K39, pin 14), energizing
nal contacts of the white and orange wires respec-
K39. This connects pins 9 and 5 of relay K39.
tively. When S66 senses its target, 12 VDC is
12 VDC present at pin 9 of relay K39 is sent out
sent from the white wire #200 to the orange wire
pin 5 to the right side pins locked relay (K40, pin
9). K40 is energized by the right hand side prox-
imity switches. The left hand side proximity
switches energize K39. The signal from K39 must
sent out orange wire #267 to S60 on the white
pass through an energized K40 down wire #283 to
wire #267. When S60 senses its target, 12 VDC
a normally open 1300 psi pressure switch. When
1300 psi of clamping pressure is achieved, then
the pressure switch will close and send the
12 VDC down wire #276 to the set coil of the
clamp pressure achieved relay (K41). This will set
sent out the orange wire #269 to the coil of the on
the relay and connect pins 10 and 5. 12 VDC is
container relay (K32, pin 14), energizing K32.
present at pin 10 of relay K41. The 12 VDC is
When K32 energizes, 12 VDC present at the com-
sent out pin 5 down wire #233. 12 VDC on wire
mon pin 9 is sent out pin 5 on wire #241 to the coil
#233 will energize the green Clamp lights and
of the unlock interlock relay (K48, pin 14), energiz-
energize relay K50.
ing K48. Additionally, 12 VDC on wire #241 is
The Left hand side of the attachment operates sent to the amber on container lights.
as follows: 12 VDC is present the red wire of
proximity switch S61. Ground is present on the Twistlock Circuit Operation (Pin System)
orange wire #211. The 12 VDC present on the (Illustration 29-59)
red wire is used for proximity switch operation The amber container light must be illuminated in
only. When the proximity switch is targeted, it will order to lock or unlock the twistlocks. The Mode
close the internal contacts of the white and orange select switch must be in the twistlock mode. To
wires. When S61 senses its target, ground is sent lock or unlock the twistlocks, depress the twistlock
from the orange wire #211 to the white wire #265. lock / unlock switch (S31). 12 VDC will be sent on
This ground is sent to the coil of the left beam wire #203 (lock twistlocks) or wire #202 (unlock
29-58 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

twistlocks) to relay (K7 or K6). The twistlock inter- the operator with a visual indication of interlock
lock relay (K14) must be energized and send logic for attachment operation. The following list
ground to the coils of relays (K6 and K7). When describes the function of each container light:
12 VDC is placed on the coils of K6 or K7. 12
1. Red Light. This light illuminates when the
VDC will be sent from pin 9 to pin 5 on wire #223
twistlocks are fully unlocked (additionally, the
(lock twistlocks) or wire #222 (unlock twistlocks),
work lights on the attachment will be illumi-
through the valve select relay (K42). K42 must be
nated).
de-energized to send control signals to the twist-
lock work section. The 12 VDC signal passes 2. Green Light. This light illuminates when the
through a de-energized K42 to either the A port twistlocks are fully locked.
or B port of the twistlock work section (WS5)
3. Amber Light. This light illuminates when the
which will shift the pilot control solenoid, allowing
attachment is fully on the container and twist-
pilot pressure to shift the main spool. From here,
locks are in the container’s corners.
the main attachment fluid flow is diverted to the
twistlock cylinders to lock or unlock the twistlocks. 4. Blue Light. This light illuminates when the pin
When the twistlocks are fully locked and the mode of operation has been selected. This
attachment is down on a container, the green and light will blink when the attachment is in the
amber container lights will be illuminated. When wide twistlock (WTP) mode of operation.
the twistlocks are fully unlocked and the attach-
ment is down on a container, the red and amber Attachment Interlock Logic For Container
container lights will be illuminated. Refer to Lights Operation (Illustration 29-59)
Attachment Interlock Logic For Container Red Light. Under normal operation, the red con-
Lights Operation for the red, green and amber tainer light will be the only light illuminated when
container lights interlock operation. approaching the container. Limit switches (S45,
In the event of an emergency or while mainte- S48, S37 and S40) will be closed. From here, the
nancing the truck, a twistlock override switch following will happen:
(S35) can be held in position to override the inter- 1. Ground is present pin 8 of limit switch (S45).
lock (amber container light circuitry) to allow the When the twistlocks are fully unlocked and the
operator to lock or unlock the twistlocks. limit switches are tripped, the following
occurs:
GREENLIGHT a. Ground at pin 8 of limit switch (S45) will be
RED LIGHT (TWISTLOCKS sent out pin 7, down wire #234 to pin 3 of
AMBER LIGHT
(TWISTLOCKS LOCKED) limit switch (S48).
(ON-CONTAINER)
UNLOCKED)
b. Ground at pin 3 of limit switch (S48) is sent
out pin 4, down wire #235 to pin 4 of limit
switch (S37).
BLUE LIGHT
(PIN MODE)
c. Ground at pin 4 of limit switch (S37) is sent
switch (S40).
d. Ground at pin 7 of limit switch (S40) is sent
out pin 8, down wire #278 to the coil of
relay (K36). If the carriages are fully
retracted, K36 will have 12 VDC on its coil
and will energize. This will place 12 VDC
on wire #237.
e. 12 VDC on the wire #237 is sent to termi-
Illustration 29-32. Container Lights nal #1 of diode bank (DB5). 12 VDC will
pass from terminal #1 to terminal #2 of
Container Lights (Illustration 29-32). The con- DB5 to the Red container light, illuminating
tainer lights are used to aid the operator in the the light. Additionally, 12 VDC on terminal
safe operation of the attachment. They provide #1 of DB5 is jumpered to terminal #5 of
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-59

DB3. 12 VDC will pass from terminal #5 to the controller enable relay (K20, see Relay
terminal #6 of DB3 down wire #289 to the K20 Operation in this section). Additional-
controller enable relay (K20, refer to Relay ly, 12 VDC on wire #233 will be sent to the
K20 Operation in this section). Additional- red container light mounted on the attach-
ly, the 12 VDC on wire #237 will provide ment, illuminating the light.
operating power to the 40-ft. expand
Amber Light. Once the attachment twistlocks are
switch (S32) and the 20-ft. retract switch
fully in the corners of the container, the on-con-
(S33). 12 VDC on wire #237 also ener-
tainer proximity switches (S46, S49, S38, and
gizes the work light relay (K19). K19 will
S41) will be energized. From here, the following
energize, connecting pins 5 to 3 and 6 to
will happen:
4. 12 VDC at pin 5 will pass out pin 3,
down wire #242 to the left work light 1. 12 VDC will be present at the red and white
(DS32), illuminating it. 12 VDC at pin 6 will wires of proximity switch (S46). 12 VDC will
pass out pin 4, down wire #242 to the right also be present on the red wires of proximity
work light (DS33), illuminating it. Addition- switches (S49, S38, and S41).
ally, 12 VDC at pin 4 of relay (K19) is sent
2. When the proximity switches (S46, S49, S38,
down wire #242 to the red container light
and S41) are sensing their targets (red L.E.D.
mounted on the attachment, illuminating
is illuminated on the back of the proximity
the light.
switches), the following occurs:
Green Light. Once the attachment twistlocks are
a. 12 VDC at the white wire #200 of proximity
fully locked, the twistlock lock limit switches (S44,
switch (S46) will be sent on the orange
S47, S36, and S39) will be energized. From here,
wire #238 to the white wire #238 of proxim-
the following will happen:
ity switch (S49).
1. Ground is present pin 4 of limit switch (S44).
b. The 12 VDC on the white wire #238 is sent
When the twistlocks are fully unlocked and the
out the orange wire #239 of proximity
limit switch (S44) is tripped, the following
switch (S49) to the white wire #239 of
occurs:
proximity switch (S38).
a. Ground at limit switch (S44) pin 4 will be
c. The 12 VDC on the white wire #239 is sent
sent out pin 3, down wire #230 to pin 7 of
limit switch (S47).
switch (S38) to the white wire #240 of
b. Ground at pin 7 of limit switch (S47) is sent proximity switch (S41).
d. The 12 VDC on the white wire #240 is sent
switch (S36).
c. Ground at pin 8 of limit switch (S36) is sent switch (S41) to the coil of relay K32 (on
out pin 7, down wire #232 to pin 3 of limit container relay). K32 will energize, and
switch (S39). send 12 VDC down wire #241 to the coil of
relay K48 (unlock interlock relay) and to
d. Ground at pin 3 of limit switch (S39) is sent
the amber on-container light mounted on
out pin 4, down wire #279 to the coil of
the attachment, illuminating the light.
relay (K35). If the carriages are fully
Additionally, 12 VDC on wire #241 is sent
retracted, K35 will have 12 VDC on its coil
to terminal #5 of diode bank (DB4).
and will energize. This will place 12 VDC
12 VDC at terminal #5 will pass out termi-
on wire #233.
nal #6 to pin 14 of the twistlock interlock
e. 12 VDC on the wire #233 is sent to termi- relay (K14), energizing K14. Ground at pin
nal #3 of diode bank (DB5). 12 VDC will 5 of K14 is sent out pin 9 to pin 13 of the
pass from terminal #3 to terminal #4 of lock and unlock relays (K7 and K6). 12
DB5 to the Green container light, illuminat- VDC on wire #241 is also sent to pin 1 of
ing the light. Additionally, 12 VDC on ter- relay (K54) and jumpered to terminal #5 of
minal #3 of DB5 is jumpered to terminal #1 diode bank (DB5). 12 VDC at terminal #5
of DB3. 12 VDC will pass from terminal #1 will pass out terminal #6 of DB5 down wire
to terminal #2 of DB3 down wire #289 to
29-60 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

#241A, illuminating the amber on-container energizing K54. Additionally, 12 VDC on wire
light. #221 is sent to terminal #3 of diode bank (DB4).
12 VDC on terminal #3 will pass out terminal #4 of
The amber on-container light must be illuminated DB4 to the output side of DB3, down wire #289 to
in order to lock or unlock the twistlocks with the the controller enable relay [(K20, pin 86), Illustra-
twistlock lock / unlock switch (S31). During main- tion 22-15].
tenance or emergencies, the on-container proximi-
ty switches may or will not be capable of seeing Relay K59 Operation (Illustrations 22-15 and
the targets which activate them (four corner plung- 29-59). Relay K59 operates as follows: 12 VDC
ers). A twistlock override switch (S35) is designed is present at pins 14 and 9 of the relay. Relay
into the circuit for this reason (refer to Twistlock K59 will energize when the operator occupies the
Override). When locking onto a container, the seat. When the operator occupies the seat, the
red container light will go out as soon as the twist- operator presence switch (OPS) will close and
locks rotate from the fully unlocked position. The pass ground to pin 13 of relay K59, energizing
amber on-container light will remain illuminated. K59. When relay K59 energizes, 12 VDC at pin 9
Once the twistlocks are in their fully locked posi- will be sent out pin 5 to the micro-switches of the
tion, limit switches (S44, S47, S36, and S39) will joystick. When the operator is not in the opera-
be energized, illuminating the green container tor’s seat, both electrical and hydraulic operations
light and the amber on-container light will remain of the joystick are suspended.
illuminated. Once the container is lifted, there is Relay K54 / K58 Operation (Illustration 29-59).
enough play designed into the plungers, allowing Relay K54 is controlled by the override key switch
the plungers to drop down which will de-energize only. K54 in conjunction with the on-container
the four on-container proximity switches to turn off proximity switches (S46, S49, S38, S41) control
the amber container light, de-energizing relay the lift soft landing solenoid. K54 operates as fol-
(K14). lows: The coil of relay K54 is controlled by pins
tion of the red or green container light will send connected to pin 14 and jumpered to diode bank
12 VDC through diode bank (DB3). The diodes (DB4) at terminal #3. The common pin 9 is con-
are used to isolate the red container light from the nected to pin 1 (wire #241) in a de-energized state
green container light. From here, the 12 VDC will and in an energized state, the common pin 9 is
be placed on wire #289 to pin 86 of the controller connected to pin 5 (no wire attached). 12 VDC is
enable relay (K20), energizing the relay provided supplied to pin 1 (wire #241) from the activation of
the operator presence switch (OPS) is closed. all four on-container proximity switches (S46, S49,
When the operator is in the seat, the OPS switch S38, S41). When 12 VDC is present at pin 9 of
will close and send ground to pin 85 of relay K20. relay K54, relay K58 will energize. When relay
When K20 energizes, 12 VDC (supplied from K58 energizes, 12 VDC at pin 9 is sent out pin 5
CB15 to pin 30) will be sent out pin 87 of K20 onto wire #90; this will energize the lift soft landing
down wire #79. This will energize the controller valve. When the lift soft landing valve is ener-
enable solenoid valve (CDS) and allow pilot pres- gized, lowering pilot pressure (from the joystick,
sure, present at port 3, to pass out port 1 of this present at port 2 of the lift soft landing valve) is
valve, and supply pilot pressure to the joystick for dead-headed at the lift soft landing valve and is
lift / tilt hydraulic functions. When the Green or not allowed to stroke the spool of the lift valve.
Red container light is not illuminated, 12 VDC will Pilot pressure, which supplied the spool of the lift
not be supplied to pin 86 of relay K20 and K20 will valve, is now vented to the hydraulic tank from
not energize unless the override switch is acti- port 1 to port 3 of the lift soft landing valve. The
vated. The override switch is a key type switch spool of the lift valve (located in the lift / tilt valve
that must be held in its closed state to override the bank) then spring returns to its neutral state and
interlock operation of the Red, Green, and Amber lowering capabilities are suspended unless the
container lights. 12 VDC is supplied to the B post override switch has been activated.
of the override switch from circuit breaker (CB18). Attachment Work Lights (Illustration 29-59). The
Activation of the override switch will send 12 VDC two attachment work lights are powered by relay
from the B post out the S post of the override (K19). When relay (K19) is de-energized, the
switch and down wire #221 to pin 14 of relay K54, internal switch connects pins (9 and 1) and pins
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-61
(12 and 4) completing the circuit of both sets of Wide Twistlock Mode Operation
pins. When the relay is energized, the coil shifts (Illustration 29-60)
the switch, connecting pins (9 and 5) and pins (12
This section explains the electrical operation of
and 8) completing the circuit of both sets of pins.
the wide twistlock mode.
This allows the 12 VDC, that was present on pin
12, to be sent on wire #242 to energize the left Depressing the mode select switch to select the
work light (DS32). Additionally, the 12 VDC, that pin mode, will send 12 VDC from the mode select
was present at pin 9, will be sent on wire #242 to switch down wire #286 to the coil of the pin mode
energize the right work light (DS33). relay K47 (pin 14) energizing the relay. When K47
energizes, 12 VDC at the common pin #9 is sent
Twistlock Override (Illustration 29-59). There is
out pin #5 to the coil of the interlock relay K14 (pin
a key-type override switch, located on the back of
#14), energizing K14. When K14 energizes,
the control stand, that is to be used only to bypass
ground, present at pin #5, is sent out the common
the interlock (amber container light circuitry) for
pin #9 to the coils of the unlock and lock relays
maintenance or emergency. The override switch
(K6 and K7, pin #13). Neither K6 nor K7 will ener-
must be held in position to override the interlock
gize until 12 VDC is placed on pin #14 of their
(amber container light circuitry) which will illumi-
coils. Additionally, 12 VDC on wire #286 is sent to
nate the amber container light, enabling the oper-
the coil of the pin mode relay (K33, pin 14) ener-
ator to lock and unlock the twistlocks by depress-
gizing K33. When K33 energizes, 12 VDC at
ing either the twistlock lock or unlock micro switch.
common pin #9 is sent out pin #5 on #281, ener-
gizing the blue lights (PIN MODE). Additionally,

The twistlock override switch 12 VDC on wire #286 is sent to the coil of the
should only be used while maintenancing the valve select relay (K42, pin #14) energizing the
machine or in an emergency. relay. K42 in an energized state will send electri-
cal control signals to the Clamp work section
instead of the twistlock work section.
Depressing the Clamp / Unclamp micro switch to
Circuit Breakers. Circuit breakers are employed the Unclamp position will send 12 VDC down wire
in the electrical system and act similar to fuses, #202 to the coil of the Unlock relay (K6, pin 14).
protecting the electrical circuits and valuable com- This will energize K6, provided the ground from
ponents from overloads which could damage the interlock relay (K14, pin 9) is present on pin
them. Perform the following troubleshooting pro- #13 of the coil of relay K6. When K6 energizes,
cedures to troubleshoot a circuit breaker. 12 VDC at the common pin #9 is sent out pin #5,
1. Turn the ignition key to the “Ignition” position. down wire #222 to the coil of the unlock relay
(K49, pin 14) K49 will energize and send 12VDC
2. If the circuit breaker is tripped, reset the circuit from pin #9 out pin #5 down wire #282 to the
breaker. unlock interlock relay (K48, pin 5). K48 will ener-
3. If the circuit breaker immediately retrips, gize when the amber on container light is illumi-
remove all wires from the output side (load nated. When K48 energizes, 12 VDC present at
side) of the circuit breaker. pin #5 will be sent out pin #9, down wire #282 to
the reset coil of the clamp pressure achieve relay
4. Reset the circuit breaker. If the circuit breaker (K41). This will reset K41 and open the contacts
retrips, the circuit breaker is bad and must be of pins 10 and 5, removing the 12 VDC from the
replaced. Green container light (clamp). Additionally, the
5. If the circuit breaker maintains a set state, one unlock interlock relay (K50) will de-energize.
of the output circuits is shorted. Reconnect 12 VDC on wire #282 is sent to pin #12 of the
the wires one by one to the output side (load valve select relay (K42). K42 is energized while in
side) until the circuit breaker trips. Trouble- the pin mode of operation. 12 VDC present at pin
shoot the circuit of the wire, that tripped the #12 is sent out on pin #8, down wire #255 to the
circuit breaker, for a short. solenoid on the B port side of the clamp work sec-
tion. The solenoid on the B port side will form an
6. Isolate and remove the short from the circuit. electro-magnet when energized. This shifts the
pilot spool cartridge, allowing pilot pressure to shift
29-62 THDC
THDC
/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
the main spool of the work section. This will divert from the white wire #211 to the orange wire #272.
system hydraulic oil to the drive motor. The car- This ground is sent to pin 9 of relay (K45). K45
riage assemblies will be moved outward. The car- was energized by the WTP switch, connecting
riage assemblies will extend until the expansion pins 9 and 5. Ground present at pin 9 will be sent
carriage out proximity switches sense their tar- out pin 5, down wire #264 to pin 13 of relay (K43),
gets. The right hand side of the attachment energizing K43. This will connect pins 12 to 8 and
operates as follows: 12 VDC is present at red 9 to 5. The Left hand side of the attachment
wire of proximity switch (S67). Ground is present operates as follows: 12 VDC is present on the
on the orange wire #211. The 12 VDC present on red wire #200 of proximity switch (S58). Ground is
the red wire is used for proximity switch operation present on the white wire #211 of proximity switch
only. When the proximity switch is targeted, it will (S58). The 12 VDC present on the red wire is
close the internal contacts of the white and orange used for proximity switch operation only. When
wires. When S67 senses its target, ground is sent the proximity switch is targeted, it will close its
from the orange wire #211 to the white wire #264. internal contacts of the white and orange wires.
This ground is sent to the coil of the right beam When S58 senses its target, ground is sent from
extended relay (K38, pin 13). This energizes K13. the white wire #211 to the orange wire #273. This
Pins 12 and 8 of relay K38 will close and pins (9 ground is sent to pin 12 of relay (K45). K45 was
and 1) will open. This removes 12 VDC from the energized by the WTP switch, connecting pins
SPVR valve and stops the flow of hydraulic oil to 12 and 8. Ground present at pin 12 will be sent
the motor. out pin 8, down wire #265 to pin 13 of relay (K37)
and to pin 13 of relay (K44), energizing both
Depress the WTP select switch. This will send
relays. When K44 energizes, 12 VDC present at
12 VDC down wire #287 to pin 14 of relay K45.
pin 9 is sent out pin 5 to relay (K43, pins 9 and
K45 will energize, connecting pins 12 to 8 and 9 to
12). Relay (K43) will energize when the right side
5 of the relay. Additionally, 12 VDC is sent to pin
WTP proximity switch (S64) senses its target.
14 of relay K46, connecting pin 9 to pin 5.
When relay (K43) energizes, pin 12 is connected
Depressing the Clamp / Unclamp micro switch to to pin 8 and pin 9 is connected to pin 5. 12 VDC,
the Clamp position will send 12 VDC down wire present at pin 12 of K43 (from K44), will be sent
#203 to the coil of the Lock relay (K7, pin 14). out pin 8, down wire #281A to the flasher (for blue
This will energize K14 provided the ground from light). 12 VDC, present on wire #281A will cause
the interlock relay (K14, pin #9) is present on pin the blue light to blink on and off, signifying that the
#13 of the coil of relay K7. When K7 energizes, twistlocks are in position for WTP operation.
12 VDC at the common pin #9 is sent out pin #5
Selecting Twistlock Mode Operation. Refer to
down wire #223 to pin #9 of the valve select relay
Twistlock Circuit Operation (Pin System) in this
(K42). K42 will be energized in the pin mode. In
section for circuit analysis.
an energized state, pin #9 is connected to pin #5
of K42. 12 VDC on pin #9 is sent out pin #5 down
wire #256 to the solenoid on the A port side of the
clamp work section. The solenoid on the A port
side will from an electro-magnet when energized.
This shifts the pilot spool cartridge, allowing pilot
pressure to shift the main spool of the work sec-
tion. This will divert system hydraulic oil to the
drive motor. The carriage assemblies will be
moved inward until they target the WTP proximity
switches (S64 and S58). The right hand side of
the attachment operates as follows: 12 VDC is
present on the red wire #200 of proximity switch
(S64). Ground is present on the white wire #211
of proximity switch (S64). The 12 VDC present on
the red wire is used for proximity switch operation
only. When the proximity switch is targeted, it will
close its internal contacts of the white and orange
wires. When S64 senses its target, ground is sent
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-63
cylinder out of the way.
BOLT
WASHER 5. Remove the bolt clamping the bellcrank to the
BOLT twistlock.
ROD END 6. Remove the bellcrank and key from the twist-
lock.
WASHERS 7. Drive out the spring pin securing the slotted
nut to the twistlock.
BELLCRANK 8. Remove the slotted nut from the twistlock.
Support the twistlock and guide block as the
slotted nut is removed.
9. Lower the twistlock and guide block from the
SLOTTED twistlock housing.
NUT
NOTE: The twistlock guide spacer and inner
SPRING bearing and race will remain within the housing.
SPACER
PIN
10. Remove the spacer and the inner bearing from
GREASE the housing.
FITTING RACE
11. Inspect the outer race for damage. If dam-
aged, use a suitable punch to drive the outer
race from the twistlock housing and replace.
Illustration 29-33. Twistlocks Removal
Twistlocks Inspection
Twistlocks Removal 1. Magnetic particle test the twistlocks (refer to
the Preventive Maintenance chart in the
The following procedures describe the removal, Appendices).
inspection, installation, and adjustment of the
twistlock assemblies: 2. Check all threaded parts for damaged or
stripped threads. Replace parts found to be
1. Position the truck on a hard, level surface, unserviceable.
apply the parking brake, and block the wheels
in both directions to prevent movement of the Twistlocks Installation
truck.
1. Install the twistlock into the guide block.
2. Lower the attachment to its lowest position.
Extend the attachment to its 40 ft. position. 2. Install the twistlock and guide block into the
Using the pile slope function, pivot the desired twistlock housing.
end of the attachment towards the ground. 3. Prior to inserting the twistlock and guide block
This allows access to the twistlocks from into the housing, add guide block spacers at
ground level. the top of the guide block (over the twistlock)
3. Shut off the engine and Lock Out & Tag Out to obtain 1 11/16” from bottom of twistlock
the truck. housing to the lifting surface of the twistlock
(see Illustration 29-35). Repeat this procedure
until the required 1 11/16” measurement is ob-

Death or Serious injury can tained.
occur from falls. Always use OSHA approved 4. Install the inner bearing and spacer.
ladders, stands or manlifts to reach high
places on the truck 5. Hand tighten the slotted nut down until it bot-
toms out, align the slotted nut with the hole
4. Remove the bolt from the rod end of the twist- drilled through the twistlock, and install the
lock cylinder. Rotate the rod end and twistlock spring pin.
29-64 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

BELLCRANK
SPRING
PIN
SLOTTED
NUT
SPACER
SPACERS
INNER
RACE
OUTER
RACE
GUIDE
KEY BLOCK
TWISTLOCK
Illustration 29-34. Twistlock Parts
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-65

4. Shut off the engine. Lock Out and Tag Out the
truck.

occur from falls. Always use OSHA approved
places on the truck.
1–11/16”
Illustration 29-35. Twistlocks Parts
Do not over tighten the slotted

nut. The twistlock must rotate freely. SIDE
PIN
6. Install the bellcrank and key onto the twistlock.
Illustration 29-36. Side Pin Removal
NOTE: Align the bellcrank with the slot of the
twistlock so that the locking bolt can be installed. 5. Remove the bolts and the side pin from the
expansion carriage.
7. Install the bolt through the bellcrank. Install
and tighten the nut. 6. Use a tap and die to remove all LoctiteR resi-
due from the bolts, and the threaded mounting
8. Apply LoctiteR 277 to the threads of the rod holes of the expansion carriage.
end / bellcrank bolt.
9. Position the rod end over the bellcrank and Side Pin Inspection
install the washers and bolt. Torque bolt to 1. Inspect all threaded parts for damaged or
150 ft-lbs. stripped threads, and repair light damage with
thread chasers. Replace parts found to be
Side Pin Removal unserviceable.
1. The twistlock guide housing and twistlock must
be removed for replacement of the side pin.
2. Position the truck on a hard level surface,
in both directions to prevent movement of the
truck.
Extend the attachment to its 40 ft. position.
Using the Pile slope function, pivot the desired
end of the attachment towards the ground.
This allows access of the twistlocks and side
pin from ground level.
29-66 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

eter is worn more than 1.580” (.160” of the
original dimension), replace the pin.
Side Pin Installation
1. Seat the pin into the housing.
2. Apply LoctiteR to the threads of the mounting
bolts. Install the bolts and flatwashers.
3. Torque the six mounting bolts to 210 ft-lbs.
4. Perform the Twistlocks Installation proce-
dures found in this section.
5. The pin (Clamp) proximity switches should be
checked for proper operation any time the side
2.250” pin has been removed before placing the truck
2.251” into service.
Illustration 29-37. Pilot Hole Inspection Pin Clamp Proximity Switch Adjustments
2. Inspect the pilot hole in the twistlock housing. Complete the following procedures to check and
The original diameter is 2.250” / 2.251” (see adjust the clamp proximity switches:
Illustration 29-37). The pilot hole must be 1. Position the truck on a hard level surface,
concentric (round). apply the parking brake, and block the wheels
truck.
Extend the attachment to its 40 ft. position.
Using the pile slope function, pivot the desired
This allows access of the twistlocks from
ground level.

occur from falls. Always use OSHA approved
3. Position 4 metal objects in front of the clamp
MINIMUM proximity switches. Use grease or tape to
ALLOWABLE secure the metal object in front of the proximity
DIAMETER switches. This procedure will require repeat-
1.590” ing procedure 2. for both end beams.
4. Shut off the engine and turn the ignition switch
to the Ignition position (One click).
Illustration 29-38. Pilot Hole Inspection
5. The Green locked light will illuminate if all 4
3. Inspect the side pin. The original diameter of proximity switches are operating properly and
the side pin is 1.745” ± .005”. The pin can be the clamp pressure switch (SPS) is made.
rotated as it wears. When the diameter is NOTES:
worn more than 1.660” (.080” of the original
dimension), rotate the pin 180 degrees. The S The L.E.D., located on the back of the proximi-
pin can only be rotated once. When the diam- ty switch, will illuminate when the proximity
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-67

switch is targeted. This does not signify that 3. Tag and disconnect all electrical connections
the internal contacts of the proximity switch to the carriage assembly.
have switched and does not prove the proximi-
4. Provide a suitable lifting device capable of
ty switch is operational.
supporting approximately 800 pounds and
S If desired, jumper the two wires of the clamp attach it to the carriage assembly.
pressure switch together. This will simulate
5. Provide a suitable container to catch draining
that clamp pressure has been achieved. With
hydraulic fluid. Tag, disconnect, and plug the
all 4 clamp proximity switches targeted, the
two hydraulic hoses to the twist lock cylinder.
green container light should illuminate.
Dispose of drained hydraulic

PROXIMITY fluid in accordance with federal and local
SWITCH regulations.
6. Disconnect the power track from the carriage
assembly.
SIDE
PIN
GREASE
RELIEF
MOUNTING
CLAMP
BOLT
SET
SCREW
30°
Illustration 29-39. Proximity Switch Adjustment

GREASE FLANGE
6. To adjust the proximity switches, remove the
FITTING NUT
outside setscrew and loosen the inner set-
screw (see Illustration 29-39). This will allow
GREASE
the proximity switch to slide in and out of the RESERVOIR
slot.
7. With a metal object approximately 1/8” in front Illustration 29-40. Grease Reservoir
of the proximity switch aperture, move the
proximity switch in or out until the L.E.D. illumi- 7. Remove the clamp from the grease reservoir.
nates. Tighten the setscrews with the proximi-
ty switch at this location. Repeat procedures 8. Remove the nuts, bolts, flatwashers, and
5. and 6. for the remaining clamp proximity spacers from the flange assembly.
switches. 9. Rotate the flange assembly 30 degrees to
align it with the through slots of the carriage
Pin System Expansion Carriage Removal (see Illustration 29-40).
1. Lower the attachment to its lowest position. 10. Remove the two bolts securing the stop plate
Select Pin mode of operation and extend the to the lug beam assembly.
expansion carriages.
11. Apply enough tension to the lifting device to
2. Apply the parking brakes, block the wheels to support to carriage assembly.
prevent movement in either direction, and
Lock Out & Tag Out the truck. 12. Slowly pull the carriage from the lug beam.
Once the carriage is clear of the lug beam,
move the carriage to a prepared work area.
29-68 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

DRIVE
MOTOR TENSION SPLIT MOTOR
BOLT NUT
DRIVE SCREW
ASSEMBLY
TRUNNION
GREASE LOCKING DRIVE LINE

FITTING BOLT ASSEMBLY
Illustration 29-41. Drive System Illustration 29-42. Drive Assembly Removal
Expansion Carriage Drive System Removal

LOCK
Perform the following procedures for removal of TACK PLATE
the drive: WELD
1. Fully open the carriage assemblies.
2. Remove the grease reservoir. TRUNNION
3. Remove the spring pin from the slotted nut
(located on the end of the screw).
4. Remove the slotted nut from the screw assem-
bly.
5. Remove the two mounting bolts from the TACK
flange nut. WELD
6. Remove the slotted nut from the screw.
TRUNNION
7. Remove the tension bolt from the drive assem- MOUNT
bly. WELDMENT
8. Remove the two mounting bolts securing the
drive motor to the lug beam. Illustration 29-43. Trunnion And Screw Removal
9. Pull the drive motor away from the motor 10. Remove the locking bolts from the split nut
mount as far as possible. This should allow and remove the split nut from the screw.
enough clearance to swivel and pull the drive
assembly on the opposite side of the motor 11. Attach an appropriate lifting device capable of
mount free of the drive motor. supporting 100 pounds to the trunnion and
screw assembly.
NOTE: If additional clearance is required, slightly 12. Grind the tack welds off the locking plates
cock the motor. Remove the drive assembly and (located on the trunnion mount weldment, see
key from the screw. Retain the key for re-assemb- Illustration 29-43).
ly.
13. Grind off the tack welds from the base of the
trunnion weldments.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-69

14. Remove the six bolts which secure the trun- 3. In the event the trunnion screw bearings
nion weldments to the lug beam assembly. require replacement, install the trunnion screw
bearings as indicated. The load side of the
15. Remove the screw and trunnion as an assem-
trunnion screw bearings must be positioned
bly (see Illustration 29-46).
towards the outside of the trunnion.
16. Move the trunnion and screw assembly to a
4. Inspect the bushings of the trunnion. Shift the
prepared work area.
trunnion up and down, and side to side while
Expansion Carriage Drive System Inspection observing for movement of the trunnion.
Excessive movement indicates a bushing has
1. Inspect all threaded parts for damaged or failed. Replace both bushings if one is found
stripped threads. Repair light damage with defective.
thread chasers. Replace parts found to be
unserviceable. 5. Inspect the splines of the drive motor and
screw. Replace parts found to be worn or
2. Inspect the trunnion screw bearings for loose- damaged.
ness, pitting, or other signs of excessive wear.
Replace both bearings if either is worn.
BUSHING
NO LOAD
SIDE FACING
INWARD
LOAD
SIDE
FACING
OUTWARD
Illustration 29-45. Trunnion Bushings
Illustration 29-44. Trunnion Screw Bearings
29-70 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

INSIDE
FACE
OUTSIDE
FACE
FLATWASHER
SEAL
SLEEVE
BUSHING TRUNNION
ASSEMBLY
FLANGE NUT
ASSEMBLY
SEAL
BEARING
SEAL LOCK
SLEEVE PIN
SLOTTED
NUT
BUSHING
BEARING
SEAL
SPLIT
FLATWASHER
NUT
SCREW
GREASE
RESERVOIR
Illustration 29-46. Trunnion and Screw Assembly
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.07/03)
06/03) 29-71
GREASE
RELIEF
MOUNTING
CLAMP
BOLT
GREASE FLANGE
FITTING NUT
GREASE
RESERVOIR
Illustration 29-48. Grease Reservoir
Flange Nut Removal

Perform the following procedures to remove the
flange nut:
1. Position the truck on a hard, level surface,
truck.
Illustration 29-47. Trunnion Seal and Sleeve Extend the attachment to its 40 ft. position.
Using the pile slope function, pivot the desired
Trunnion Seal and Seal Sleeve Installation end of the attachment towards the ground.
This allows access of the flange nut from
1. Install the trunnion screw bearings into the ground level.
trunnion as indicated.
2. Install the seal sleeve into the trunnion with
the lip towards the trunnion, flat side of seal
sleeve facing out (see Illustration 29-47). occur from falls. Always use OSHA approved
3. Install the seal with the spring side facing out. places on the truck.
4. Install the flat washer onto the screw prior to 3. Remove the grease reservoir.
inserting the screw through the trunnion.
NOTE: The flat washer must be on the side
towards the grease reservoir.
29-72 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

FLANGE Extend the attachment to its 40 ft. position.
NUT Using the pile slope function, pivot the desired
SCREW
This allows access of the flange nut from
ground level.
3. Remove the grease reservoir.
SLOTTED
NUT
SPACER
TRUNNION
1/8” SCREW
BOLT
WASHER
FLANGE EXPANSION
NUT CARRIAGE
SPRING
PIN
Illustration 29-49. Screw Assembly
5. Remove the spring pin from the slotted nut.

6. Remove the slotted nut Illustration 29-50. Trunnion and Flange Nut
7. Remove the flange nut mounting bolts and
spacers. 5. Install the flange nut on the screw. Rotate the
flange nut clockwise or counterclockwise
8. Remove the flange nut from the screw. Rotate (dependent on which side of the attachment
the flange nut clockwise or counterclockwise the flange nut is located on).
(dependent on which side of the attachment
the flange nut is located on). 6. Install the spacers and the flange nut mount-
ing bolts (see Illustration 29-50).
Flange Nut Installation
NOTE: When installing the spacers, ensure that
1. Position the truck on a hard, level surface, the spacer is in good condition, and that an 1/8”
apply the parking brake, and block the wheels gap is attained between the flange nut assembly
in both directions to prevent movement of the and the lug beam.
truck.
7. Install the slotted nut.

Death or Serious injury can 8. Remove the spring pin from the slotted nut.
occur from falls. Always use OSHA approved 9. Remove the grease reservoir.
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.07/03)
06/03) 29-73
Slider Bearing Replacement and Shimming the distance on the outside of the expansion
carriage rails from side to side and top to
The expansion carriage must be removed in order
bottom (see Illustration 29-52).
to properly shim the slider bearings.
MEASURE & RECORD

MEASURE & RECORD
DISTANCES
DISTANCES
MEASURE & RECORD

DISTANCES
Illustration 29-51. Lug Beam Measuring
1. Once the expansion carriage has been Illustration 29-53. Expansion Carriage Measuring
removed from the lug beam, measure and
record the distance inside the lug beam track 3. Measure, combine and record the thickness of
from side to side and top to bottom (see both opposing slider bearings (set, see Illustra-
Illustration 29-51). tion 29-53).
NOTE: Replace the slider bearings when the
bearing thickness is worn to 3/16”. Replace the
MEASURE & RECORD slider bearings as a set to prevent uneven wear,
DISTANCE
binding and / or premature wear of new bearings.
4. Subtract the measurements recorded in proce-
dure 2. from the measurements recorded in
procedure 1. Record this measurement.
5. Subtract the measurement recorded in proce-
dure 3. from the measurement recorded in
procedure 4. Subtract 1/16” from this sum.
The balance is the required thickness of the
shim pack. Divide the total required shim pack
thickness by two and equally install the shims
underneath the opposing slider bearings (set).
MEASURE & RECORD 6. When the slider bearings are equally and
DISTANCE properly shimmed, apply LoctiteR 277 to the
threads of the counter sunk bolts. Torque the
Illustration 29-52. Expansion Carriage Measuring slider bearing socket head bolts to 14-16 ft-lbs
and center punch the heads of the bolts to
2. Remove the slider bearings and shims from lock in place.
the expansion carriage. Measure and record
29-74 THDC
THDC/ THDCP
/ THDCP- 954
- 954/ 955
/ 955/ 974
/ 974/ 975
/ 975(Rev.
(Rev.06/03)
7/03)
Expansion Carriage Inspection the expansion carriage. Install the two flange
nut mounting bolts.
1. Inspect the expansion carriage welds for
cracks. Refer to SIRR in the Appendices for 8. Reconnect all electrical components and
typical inspection points. hydraulic hoses.
2. Inspect the slider bearings for cracks, chunk-
ing or excessive wear. Replace worn or dam-
aged slider bearings as a set.
3. Inspect all threaded components for damaged
or stripped threads. Replace all damaged
components.
CENTER OF LUG
Expansion Carriage Installation BEAM
1. Lower the attachment to its lowest position. 44–31/64” 44–31/64”

2. Apply the parking brakes, block the wheels to 88–31/32”
prevent movement in either direction, and CENTER TO CENTER OF TWISTLOCKS
Lock Out & Tag Out the truck.
3. Perform the Slider Bearing Replacement Illustration 29-54. Fully Retracted Measurements
and Shimming procedures, found in this sec-
tion, prior to installation.
Expansion Carriage Alignment

Death or Serious injury can Perform the following procedures whenever the
occur from falls. Always use OSHA approved expansion carriages or the limit switches have
ladders, stands or manlifts to reach high been removed.
places on the truck. Alignment Check
4. Provide a suitable lifting device capable of 1. Operate the expansion carriages to their fully
supporting approximately 800 pounds and RETRACTED position. The proximity target
attach it to the carriage assembly. will activate the proximity switches and illumi-
5. Lubricate the sliding surfaces of the lug beam nate the red container light. Activation of the
assembly and slider bearings with a good retract proximity switch does not stop move-
grade of grease. Refer to the Fuel and Lubri- ment of the carriages. The carriages are
cant Specifications found in the Appen- stopped when they contact the stop plate
dices. welded to the lug beam assembly.
6. Lift the expansion carriage and align it with the 2. Measure the distance between the tips of the
lug beam. Slide the expansion carriage into two twistlocks (center to center, see Illustration
the lug beam half way. Ensure that the flange 29-54). This measurement must equal
nut is properly aligned with the slot located at 88 31/32 inches.
the end of the carriage. Carefully slide the 3. Mark the center of the lug beam assembly.
expansion carriage completely into lug beam. Measure the distance from the center mark to
7. When the expansion carriage has been the tips of each twistlock (see Illustration
inserted past the flange nut, rotate the flange 29-55). These measurements must equal
nut until it aligns with the mounting holes on 44 31/64 inches
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.07/03)
06/03) 29-75
4. Repeat procedures 2. and 3. for the opposite
side of the attachment. CROSS CHECK
CENTER OF LUG
BEAM
61.5” 61.5”
123”
TWISTLOCK TIPS
CENTER TO CENTER OF TWISTLOCKS (CENTER TO CENTER)
Illustration 29-55. Fully Extended Measurements Illustration 29-56. Cross Check Measurement
5. Extend the carriages to their fully EXTENDED 10. Fully retract the expansion carriages. Mea-
position. The expansion of the carriages is sure and record the distance from the left front
controlled (stopped) by the expansion carriage twistlock to the right rear twistlock (center to
extended proximity switches. When the center).
expansion carriages are fully extended, a tar- 11. Measure and record the distance from the left
get will activate the extended proximity rear twistlock to the right front twistlock (center
switches, illuminating the red container light to center).
and stopping any further outward movement of
the carriages. 12. The measurements recorded in procedures
10. and 11. must equal each other.
6. Measure the distance between the tips of the
two twistlocks (center to center, Illustration 13. Repeat procedures 10. through 12. with the
29-55). This distance should equal 123 expansion carriages fully extended.
inches.
7. Mark the center of the lug beam assembly.
Measure the distance from the center mark to
the tips of each twistlock (see Illustration
29-55). These measurements should equal
61.5 inches.
8. Repeat procedures 5. through 7. for the oppo-
site end of the attachment.
9. If procedure 6. is not 123 inches, then adjust-
ment of the expansion carriage extended prox-
imity switch is required.
29-76 THDC
THDC/ THDCP
/ THDCP- 954
- 954/ 955
/ 955/ 974
/ 974/ 975
/ 975(Rev.
(Rev.06/03)
7/03)
EXPANSION
TWISTLOCK CARRIAGE PIN SYSTEM EXPANSION CARRIAGE WIDE
SOFT LANDING EXTENDED SOFT LANDING RETRACTED TWISTLOCKS
PROXIMITY PROXIMITY PROXIMITY PROXIMITY SWITCH PROXIMITY
SWITCH SWITCH SWITCH SWITCH
PIN SYSTEM
SOFT LANDING
PROXIMITY
SWITCH
TWISTLOCK
PIN SYSTEM SOFT LANDING
CLAMP PROXIMITY PROXIMITY PIN SYSTEM
SWITCH SWITCH CLAMP PROXIMITY
SWITCH
Illustration 29-57. Proximity Switch Locations Illustration 29-58. Proximity Switch Locations
(Left Rear and Right Front) (Left Front and Right Rear)
Soft Landing (Pin Mode) switched and does not prove the proximity switch
is operational.
Perform the following procedures to adjust the soft
landing proximity switches: 4. The amber on-container light should illuminate
if all 4 on-container proximity switches are acti-
1. Lower the attachment to its lowest position. vated.
5. If one of the proximity switches fails to ener-

Death or Serious injury can gize when the soft landing pedal is raised into
occur from falls. Always use OSHA approved position, loosen the mounting bracket and
ladders, stands or manlifts to reach high re-position the proximity switch 1/8” to 1/4”
places on the truck. from the surface of the target.
2. Shut off the engine and turn the ignition switch 6. Provided the proximity switch has power and
to the ignition position (one click) is operational, the L.E.D. on the back will illu-
minate. Ensure that when the soft landing
3. Push the soft landing pedal level with the land- pedal is lowered that the proximity switch
ing pad surface. If the proximity switch is de-energizes.
operating correctly and is within the targeting
window (adjustment), the proximity switch 7. Repeat procedures 5. and 6. as required for
should energize. the remaining proximity switches.
NOTE: The L.E.D. located on the back of the

proximity switch will illuminate when the proximity
switch is targeted. This does not signify that the
internal contacts of the proximity switch have
THDC
THDC//THDCP
THDCP--954
954//955
955//974
974//975
975(Rev.
(Rev.07/03)
06/03) 29-77
Hoist Circuit
29-78 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Hoist Circuit

FOLDER ENVELOPES:
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-79
Hoist Circuit
29-80 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Optional Corner Mounted Lock / Unlock Proximity Switches
Introduction. This section contains electrical, expansion switch down wire #214 through a diode
hydraulic, and mechanical operational information bank, down wires #244 and #246, resetting the
for the attachment that employs the optional, four- double-latching relays (K15 and K16).
corner-mounted lock / unlock proximity switches 20 FT. Retract Circuit Operation (Illustration
twistlock system. 29-29). The twistlock must be fully unlocked (red
Attachment Proximity Switches Locations. container light illuminated) before 12 VDC operat-
Refer to Illustrations 29-63 and 29-64 for the loca- ing power is supplied to wire #237 on the 20-ft.
tions of the attachment proximity switches. expand switch (S33). To select the 20-ft. position,
depress the 20-ft. retract switch (S33) to the start
40 FT. Expand Circuit Operation (Illustration
position and release. 12 VDC will be sent on wire
29-29). The twistlocks must be fully unlocked (red
#213 to pin 14 of the double-latching relay (K16)
container light illuminated) before 12 VDC operat-
which will set the relay. Wire #200, which has
ing power is supplied to wire #237 for the 40-ft.
12 VDC on it from a 15 amp circuit breaker (CB20)
expand switch (S32). To select the 40-ft. position,
and is connected to pins (6 and 10). In a set state
depress the 40-ft. expand switch (S32) to the start
(red flag is visible in window), pin 10 is connected
position and release. 12 VDC will be sent on wire
to pin 5 while pin 6 is connected to pin 8. In a set
#212 to pin 14 of the double-latching relay (K15)
state, 12 VDC will be sent from pin 6 to pin 8
which will set the relay. Wire #200, which has 12
down wire #252 to port B of the retract work sec-
VDC on it from a 15 amp circuit breaker (CB20), is
tion (WS4) which will shift the pilot control sole-
connected to pins 6 and 10 of K15. In a set state
noid, allowing pilot pressure to shift the main
(red flag is visible in window), pin 10 is connected
spool. From here, the hydraulic fluid flow is
to pin 5 while pin 6 is connected to pin 8. In a set
diverted to the rod end of the expansion cylinders
state, 12 VDC will be sent from pin 6 to pin 8 on
(retracting the cylinders).
wire #251 to port A of the expansion work section
(WS4) which will shift the pilot control solenoid, While in the set state, double-latching relay (K16)
allowing pilot pressure to shift the main spool. will close the contact points of pins 10 and 5
From here, hydraulic fluid flow is diverted to the which will send 12 VDC down wire #247 to a
piston end of the expansion cylinders (extending diode bank (refer to Diodes in the Component
the cylinders). Troubleshooting), energizing the strobe and
audible alarm. At the same time, 12 VDC on wire
While in the set state, double-latching relay (K15)
#247 will be sent to proximity switch S42 (red and
will close the contact points of pins 10 and 5,
white wires) and proximity switch S50 (red wire).
sending 12 VDC out wire #248 to a diode bank
When proximity switch (S42) senses its target, it
(refer to Diodes in the Component Trouble-
will energize, connecting the contact points of the
shooting), energizing the strobe and audible
white and orange wires. Once this happens,
alarm. At the same time, 12 VDC on wire #248
12 VDC is sent out the orange wire #243 to the
will be sent to proximity switch S43 (red and white
white wire #243 of proximity switch (S50). When
wires) and proximity switch S51 (red wire). When
proximity switch (S50) senses its target, it will
close the contact points of its white and orange
energize, connecting the contact points of the
wires, sending 12 VDC down wire #244 which will
white and orange wires. Once this happens,
reset the double-latching relay (K16). Once the
12 VDC is sent out the orange wire #245 to the
double-latching relay (K16) resets, it will open the
white wire #245 of proximity switch (S51). When
contact points of pins (10 and 5) and pins (6 and
8), removing 12 VDC from wires #247 and #252.
close the contact points of its white and orange
wires, sending 12 VDC down wire #246, which will If the 20-ft. retract has been selected, the retract
reset the double-latching relay (K15). Once the movement can be stopped at any time by
double-latching relay (K15) resets, it will open the depressing the 20-ft. retract switch (S33) to the
contact points of pins (10 and 5) and pins (6 and stop position. This will send 12 VDC from the
8) removing 12 VDC from wires #248 and #251. retract switch to wire #214 through a diode bank,
on wires #244 and #246, resetting the double-
If the 40-ft. expansion has been selected, the
latching relays (K15 and K16).
expansion movement can be stopped at any time
by depressing the 40-ft. expansion switch (S32) to Twistlock Circuit Operation (Illustration 29-70).
the stop position. This will send 12 VDC from the The amber container light must be illuminated in
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-81

order to lock or unlock the twistlocks. To perform light illuminated when approaching the container.
the twistlock lock or unlock function depress the The red light operates as follows: 12 VDC is pres-
twistlock lock / unlock switch (S31). 12 VDC will ent at both the white and red wires of proximity
be sent on wire #203 (lock twistlocks) or wire #202 switch S45. 12 VDC is present on the red wire
(unlock twistlocks) to relay (K7 or K6). The twist- only of proximity switches S48, S37 and S40. The
lock interlock relay (K14) must be energized to 12 VDC present on the red wires is used for prox-
pass ground from pin 5 to pin 9 to pin 13 of relays imity switch operation only. As each of the prox-
(K6 and K7) which will complete the path for cur- imity switches is targeted, they close the internal
rent flow to relays (K6 and K7) coils, energizing contacts of the white and orange wires respective-
relay (K6 or K7). Once the relay coil is energized, ly. When S45 senses its target, 12 VDC is sent
12 VDC will be sent from pin 9 to pin 5 on wire from the white wire #200 to the orange wire #234.
#223 (lock twistlocks) or wire #222 (unlock twist- This voltage is sent to the white wire #234 of S48.
locks) to port A or port B of the twistlock work sec- When S48 senses its target, the internal contacts
tion (WS5) which will shift the pilot control sole- close and the 12 VDC on wire #234 is sent out
noid, allowing pilot pressure to shift the main orange wire #235 to S37 on the white wire #235.
spool. From here, the main attachment fluid flow When S37 senses its target, 12 VDC is sent from
is diverted to the twistlock cylinders to lock or the white wire #235 to the orange wire #236. This
unlock the twistlocks. When the twistlocks are ful- voltage is sent to the white wire #236 of S40.
ly locked and the attachment is down on a con- When S40 senses its target, the internal contacts
tainer, the green and amber container lights will be close and the 12 VDC on wire #236 is sent out
illuminated. When the twistlocks are fully wire #237. 12 VDC on the wire #237 is sent to
unlocked and the attachment is down on a con- terminal #1 of diode bank (DB5). 12 VDC will
tainer, the red and amber container lights will be pass from terminal #1 to terminal #2 of DB5 to the
illuminated. Refer to Attachment Interlock Logic Red container light, illuminating the light. Addi-
For Container Lights Operation for the red, tionally, 12 VDC on terminal #1 of DB5 is jump-
green and amber container lights interlock opera- ered to terminal #5 of diode bank (DB3). 12 VDC
tion. will pass from terminal #5 to terminal #6 of DB3
down wire #289 to the controller enable relay
In the event of an emergency or while mainte- (K20, see Relay K20 Operation). Additionally,
nancing the truck, a twistlock override switch the 12 VDC on wire #237 will provide operating
(S35) can be held in position to override the inter- power to the 40-ft. expand switch (S32) and the
lock (amber container light circuitry) to allow the 20-ft. retract switch (S33). 12 VDC on wire #237
operator to lock or unlock the twistlocks. also energizes the work light relay (K19). K19 will
Container Lights. The container lights, located in energize, connecting pins 5 to 3 and 6 to 4. 12
the cab, are used to aid the operator in the safe VDC at pin 5 will pass out pin 3, down wire #242
operation of the attachment. They provide the to the left work light (DS32), illuminating it. 12
operator with a visual indication of interlock logic VDC at pin 6 will pass out pin 4, down wire #242
for attachment operation. The following list to the right work light (DS33), illuminating it. Addi-
describes the function of each container light. tionally, 12 VDC at pin 4 of relay (K19) is sent
1. Red Light. This light illuminates when the down wire #263 to the red container light mounted
twistlocks are fully unlocked (additionally, the on the attachment, illuminating the light.
work lights on the attachment will be illumi- Green Light Operation (Locked). The green
nated). light operates as follows: 12 VDC is present at
2. Green Light. This light illuminates when the both the white and red wires of proximity switch
twistlocks are fully locked. S44. 12 VDC is present on the red wire only of
proximity switches S47, S36 and S39. The
3. Amber Light. This light illuminates when the 12 VDC present on the red wires is used for prox-
attachment is fully on the container and twist- imity switch operation only. As each of the prox-
locks are in the container’s corners. imity switches is targeted, they close the internal
Attachment Interlock Logic For Container contacts of the white and orange wires respective-
Lights Operation (Illustration 29-70) ly. When S44 senses its target, 12 VDC is sent
from the white wire #200 to the orange wire #230.
Red Light Operation (Unlocked). Under normal This voltage is sent to the white wire #230 of S47.
operation, the red container light will be the only When S47 senses its target, the internal contacts
29-82 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

RIGHT
S44 S48
(Locked) S46 S49 (Unlocked)
(On Container) (On Container) S47
S45
(Locked)
(Unlocked)
S50
(Right Frame
20’)
S42
(Left Frame
20’)
S51
(Right Frame
40’)
TRUCK
S43
(Right Frame
40’)
S40
S36 (Unlocked)
(Locked)
S38 S41
S37 (On Container) (On Container)
(Unlocked) S39
(Locked)
LEFT
Illustration 29-61. Proximity Switch Locations (Optional)
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-83

S51
40 FT. EXPAND
PROXIMITY SWITCH
(Wide Frame)
S42
20 FT. RETRACT
PROXIMITY SWITCH
(Narrow Frame)
S50
20 FT. RETRACT
ATTACHMENT END PROXIMITY SWITCH
JUNCTION BOX (Wide Frame)
(RIGHT END)
RIGHT
S43
40 FT. EXPAND
PROXIMITY SWITCH
(Narrow Frame)
TRUCK SIDE
TWISTLOCK ATTACHMENT END

LOCK / UNLOCK JUNCTION BOX
PROXIMITY SWITCHES (LEFT END)
ON CONTAINER ATTACHMENT MAIN

PROXIMITY SWITCH JUNCTION BOX
LEFT
NOTE: Refer to Illustration 29-61 for Proximity

Switch locations on Attachment
Illustration 29-62. Attachment Electrical Components
29-84 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

close and the 12 VDC on wire #230 is sent out Relay K20 Operation (Illustrations 22-15 and
orange wire #231 to S36 on the white wire #231. 29-70). Relay K20 operates as follows: illumina-
When S36 senses its target, 12 VDC is sent from tion of the red or green container light will send
the white wire #231 to the orange wire #232. This 12 VDC through a bank of three diodes (DB3).
voltage is sent to the white wire #232 of S39. The diodes are used to isolate the red container
When S39 senses its target, the internal contacts light from the green container light. From here,
close and the 12 VDC on wire #232 is sent out the 12 VDC will be placed on wire #289 to pin 86
wire #233. 12 VDC on the wire #233 is sent to of the controller enable relay (K20), energizing the
terminal #3 of diode bank (DB5). 12 VDC will relay provided the operator presence switch
pass from terminal #3 to terminal #4 of DB5 to the (OPS) is closed. When the operator is in the seat,
Green container light, illuminating the light. Addi- the OPS switch will close and send ground to pin
tionally, 12 VDC on terminal #3 of DB5 is jump- 85 of relay K20. When K20 energizes, 12 VDC
ered to terminal #1 of diode bank (DB3). 12 VDC (supplied from CB15 to pin 30) will be sent out pin
will pass from terminal #1 to terminal #2 of DB3 87 of K20 down wire #79. This will energize the
down wire #289 to the controller enable relay controller enable solenoid valve (CDS) and allow
(K20, see Relay K20 Operation). 12 VDC on pilot pressure present at port 3 to pass out port 1
wire #233 also energizes the relay (K29). K29 will of this valve, and supply pilot pressure to the joys-
energize, connecting pins 9 and 5. 12 VDC at pin tick for lift / tilt hydraulic functions. When the
9 will pass out pin 5, down wire #262 to the green Green or Red container light is not illuminated,
container light mounted on the attachment, illumi- 12 VDC will not be supplied to pin 86 of relay K20
nating the light. and K20 will not energize unless the override
sent out the orange wire #239 to S38 on the white Relay K59 Operation (Illustrations 22-15 and
wire #239. When S38 senses its target, 12 VDC 29-70). Relay K59 operates as follows: 12 VDC
is sent from the white wire #239 to the orange wire is present at pins 14 and 9 of the relay. Relay
#240. This voltage is sent to the white wire #240 K59 will energize when the operator occupies the
of S41. When S41 senses its target, the internal seat. When the operator occupies the seat, the
contacts close and the 12 VDC on wire #240 is operator present switch (OPS) will close and pass
sent out wire #241 to pin 14 of the twistlock inter- ground to pin 13 of relay K59, energizing K59.
lock relay (K14), energizing K14. When K14 ener- When relay K59 energizes, 12 VDC at pin 9 will
gizes, ground at pin 5 is sent out pin 9 to pin 13 of be sent out pin 5 to the micro-switches of the joys-
relays (K6 and K7). 12 VDC on wire #241 is sent tick. When the operator is not in the operator’s
to terminal #5 of diode bank (DB5). 12 VDC will seat, both electrical and hydraulic operations of
pass from terminal #5 to terminal #6 of DB5 to the the joystick are suspended.
Amber on-container light, illuminating the light.
12 VDC on wire #241is additionally sent to pin 1
on the attachment.
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-85
13 and 14. Ground is connected to pin 13. Wire Twistlocks Proximity Switches Adjustment
#221, from the override key switch terminal S, is Unlock Proximity Switches. Perform the follow-
connected to pin 14 and jumpered to diode bank ing procedures to adjust the twistlock unlock prox-
(DB4) at terminal #3. The common pin 9 (wire imity switches for proper operation. Refer to
#90) is connected to pin 1 (wire #241) in a de-en- Illustrations 29-63 and 29-62 for the unlock prox-
ergized state and in an energized state, the com- imity switches locations.
mon pin 9 is connected to pin 5 (no wire at-
tached). 12 VDC is supplied to pin 1 (wire #241) 1. Unlock the twistlocks. Align the twistlocks to
from the activation of all four on-container proximi- be parallel with the guide blocks in the twistlock
ty switches (S46, S49, S38, S41). When 12 VDC housings (unlocked position) by adjusting the
is present at pin 9 of relay K54, relay K58 will rod ends of the twistlock cylinder and tie rod.
energize. When relay K58 energizes, 12 VDC at
pin 9 is sent out pin 5 onto wire #90; this will ener- NOTE: It will be necessary to use the twistlock
gize the lift soft landing valve. When the lift soft override switch to unlock the twistlocks.
landing valve is energized, lowering pilot pressure
(from the joystick, present at port 2 of the lift soft 2. Beginning at the right front twistlock, adjust the
landing valve) is dead-headed at the lift soft land- unlock proximity switch (S45) in the clamp
ing valve and is not allowed to stroke the spool of towards the prox target (see Illustration 29-65)
the lift valve. Pilot pressure, which supplied the until the red L.E.D. on the rear of the proximity
spool of the lift valve, is now vented to the hydrau- switch illuminates. After the proximity switch
lic tank from port 1 to port 3 of the lift soft landing L.E.D. illuminates, continue to slide the prox-
valve. The spool of the lift valve (located in the lift imity switch 1/8” towards the prox target before
/ tilt valve bank) then spring returns to its neutral tightening the proximity switch in place.
state and lowering capabilities are suspended un- 3. Repeat procedure 2. for the remaining
less the override switch has been activated. twistlocks in the following order: right rear
Override Switch (Illustration 29-70). There is a twistlock (S48), left front twistlock (S37) and
key type override switch, located on the back of left rear twistlock (S40). The red container
the control stand, that is used to bypass the inter- light should illuminate after the left rear prox-
lock circuitry (red, green and amber container imity switch (S40) is adjusted.
lights). The override switch operates as follows: Lock Proximity Switches. Perform the following
The switch must be held into the on position for procedures to adjust the twistlock lock proximity
12 VDC to be present at the B terminal. When switches for proper operation. Refer to Illustra-
this switch is activated, 12 VDC will be sent out tions 29-64 and 29-62 for the lock proximity
terminal S (wire #221) to the coil of relay K54. switches locations.
This will energize K54 and open the circuit of the
lift soft landing solenoid, de-energizing the lift soft 1. Lock the twistlocks. Twistlocks should turn
landing valve. This allows lowering pilot pressure 90_$3_.
to reach the spool of the lift valve even when the
NOTE: It will be necessary to use the twistlock
override switch to lock the twistlocks.
minal #3. With the override switch activated, 2. Beginning at the right front twistlock, adjust the
12 VDC will pass from terminal #3 out terminal #4 unlock proximity switch (S44) in the clamp
of diode bank DB4. Terminal #4 of DB4 is con- towards the prox target (see Illustration 29-65)
nected to diode bank DB3, terminal #2. The out- until the red L.E.D. on the rear of the proximity
puts of DB3 are all jumped together and con- switch illuminates. After the proximity switch
nected to wire #289. Wire #289, in conjunction L.E.D. illuminates, continue to slide the prox-
with the seat belt switch (S18), control the control- imity switch 1/8” towards the prox target before
ler enable relay K20 (see Relay K20 Operation). tightening the proximity switch in place.
3. Repeat procedure 2. for the remaining

The override switch should twistlocks in the following order: right rear
only be used while maintenancing the machine twistlock (S47), left front twistlock (S36) and
or in an emergency. left rear twistlock (S39). The green container
29-86 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
S36 S45
S37 S44
S36 FRONT S45

(Locked) (Unlocked)
S37 S44
(Unlocked) (Locked)
LEFT SIDE RIGHT SIDE
S39 S48
(Locked) (Unlocked)
S40 S47
(Unlocked) (Locked)
TRUCK SIDE
S39 S48
S40 S47
Illustration 29-63. Prox Targets Sensed By Proximity Switches When Twistlocks Are Unlocked
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-87

S36 S45
S37 S44
S36 FRONT S45

(Locked) (Unlocked)
S37 S44
(Unlocked) (Locked)
LEFT SIDE RIGHT SIDE
S39 S48
(Locked) (Unlocked)
S40 S47
(Unlocked) (Locked)
TRUCK SIDE
S39 S48
S40 S47
Illustration 29-64. Prox Targets Sensed By Proximity Switches When Twistlocks Are Locked
29-88 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

TWISTLOCK
LOCK / UNLOCK
PROXIMITY
SWITCHES
TIE ROD
PROX
GUIDE
TARGET
BLOCK
TWISTLOCK
ROD END
HOUSING
TWISTLOCK
PIVOT
BUSHING
TWISTLOCK
CYLINDER
ROD END
ROD
END
TIE ROD
RED
L.E.D.
GUIDE
BLOCK
PROXIMITY
SWITCH
TWISTLOCK
Illustration 29-65. Twistlocks Proximity Switches Adjustment
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 29-89

1/8” - 1/4”
SLOTTED BRACKET ON-CONTAINER

PROXIMITY SWITCH
BOLT
COLLAR
PLUNGER
BOTTOM OF 1/4”
TWISTLOCK
HOUSING
Illustration 29-66. On-Container Plunger

light should illuminate after the left rear prox- 2. Loosen both bolts that secure the on-container
imity switch (S39) is adjusted. proximity switch slotted bracket to the twistlock
On-Container Proximity Switches Adjustment. housing.
Perform the following procedures to adjust the on- 3. Position the plunger at 1/4” from the bottom of
container proximity switches for proper operation. the twistlock housing.
Refer to Illustrations 29-61, 29-62, and 29-66 for
the unlock proximity switches locations. 4. Slowly move the proximity switch downward
towards the plunger collar until the proximity
1. Raise the on-container plunger so that the switch energizes (red L.E.D. on the backside
proximity switch may be adjusted to 1/8” - 1/4” of proximity switch is illuminated) and continue
from plunger collar.
29-90 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
to lower the proximity switch an additional 8. Lift the container (the amber light should go
1/16” - 1/8” and tighten both bolts. out). If amber container light fails to go out
when the container is lifted, repeat procedures
5. Check the system by lowering the attachment
2. through 8.
onto an empty container.
9. Set the container down (the amber container
6. Ensure that the amber on-container light is illu-
light should illuminate). If the amber container
minated.
light does not illuminate, the twistlock override
7. Activate the twistlocks lock switch (green and must be used to unlock the twistlocks from the
amber container lights are illuminated). container (repeat procedures 2. through 9.).
Container Attachment Troubleshooting

Some of the components described in this trouble-
shooting chart are optional equipment.
1. Red light will not illu- 1. Twistlocks are not fully unlocked. 1. Fully unlock the twistlocks.
minate (twistlocks
2. Bulb of red light is blown. 2. All three container light bulbs can
did rotate)
Replace blown bulb.
3. One of the proximity switches 3. Fully unlock twistlocks and adjust
(S45, S48, S37 and S40) is not proximity switch at fault to sense
sensing its target. its target. With the twistlocks fully
unlocked, the red L.E.D. (in the
back of the proximity switches)
should be illuminated, indicating
that the proximity switches are
sensing their targets.
(S45, S48, S37 and S40) is defec- indicates that the proximity
tive. switch’s coil did energize. It does
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-91
2. Red light will not illu- 1. Defective relay (K6). 1. Replace defective relay (K6).
minate (twistlocks Refer to Single-Pole, Single-
vated) bleshooting.
2. Defective twistlock unlock micro 2. Replace defective micro switch
switch (S31). (S31).
bleshooting.
noid.
section.
11. Defective B port relief valve in the 11. Replace B port relief valve.
3. No container attach- 1. 15 amp circuit breaker (CB20) is 1. Replace or reset circuit breaker
ment lights will illu- defective or tripped. (CB20).
minate
Deutsch connector.
4. Amber light will not 1. Bulb of amber light is blown. 1. All three container light bulbs can
illuminate be checked by depressing the
Replace blown bulb.
continued
29-92 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
4. Amber light will not 2. Loose connection or pin broken at 2. Isolate and repair.
illuminate electrical connector.
(Continued)
3. One of the proximity switches 3. Adjust the proximity switch at fault
(S46, S49, S38 and S41) is not to sense its target.
sensing its target.
5. If the red L.E.D. is illuminated, this
5. One of the proximity switches indicates that the proximity
(S46, S49, S38 and S41) is defec- switch’s coil did energize. It does
tive. not indicate that the contact points
7. Damaged container corner. 7. Report damaged container to the
proper authority.
5. Amber light will not 1. Loose, broken or shorted wire. 1. Isolate and repair wire.
illuminate (twistlock
override switch was
activated)
5. Defective override switch (S35). 5. Replace override switch (S35).
Replace blown bulb.
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-93
6. Green light will not 1. Twistlocks are not fully locked. 1. Fully lock the twistlocks.
illuminate (twistlocks
2. Bulb of green light is blown. 2. All three container light bulbs can
did rotate)
Replace blown bulb.
4. One of the proximity switches 4. Fully lock twistlocks and adjust
(S44, S47, S36 and S39) is not proximity switch at fault to sense
sensing its target. its target. With the twistlocks fully
locked, the red L.E.D. (in the back
of the proximity switches) should
be illuminated, indicating that the
proximity switches are sensing
their targets.
6. If the red L.E.D. is illuminated, this
6. One of the proximity switches indicates that the proximity
(S44, S47, S36, and S39) is switch’s coil did energize. It does
defective. not indicate that the contact points
7. Green light will not 1. Defective relay (K7). 1. Replace defective relay (K7).
illuminate (twistlocks Refer to Single-Pole, Single-
vated) bleshooting.
2. Defective twistlock lock micro 2. Replace defective unlock micro
continued electrical connector.
29-94 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
7. Green light will not 4. .3 amp circuit breaker (CB17) is 4. Replace or reset circuit breaker
illuminate (twistlocks defective or tripped. (CB17).
vated) 6. Defective relay (K14). 6. Replace defective relay (K14).
(Continued) Refer to Single-Pole, Single-
bleshooting.
noid.
section.
expansion the exception of the bulb being
chart.
2. Defective 40 ft. expand switch 2. Replace 40 ft. expand switch
(S32). (S32).
7. Mis-adjusted A port relief valve in 7. Adjust A port relief valve and set
continued expansion work section.
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-95
8. No or slow 40 FT. 9. Defective solenoid on the A port of 9. Refer to Solenoids in the Compo-
expansion the expansion work section. nent Troubleshooting to trouble-
noid.
section.
13. One of the expansion cylinders 13. Isolate and repack expansion cyl-
packing is defective. inder. To isolate the defective cyl-
inder, perform the following:
a. With the attachment is in the
20 ft. position, remove the
ton ends of both expansion
cylinders and plug them.
b. In the attachment main junc-
tion box, install a jumper wire
at terminal #200 and start the
truck.
c. Touch the jumper wire to the B
port solenoid post of the
expansion work section. This
will direct the main flow of
hydraulic fluid to the rod end of
the expansion cylinders.
d. Observe the open ports on the
piston end of the expansion
cylinders. If a flow of fluid is
retract the exception of the bulb being
chart.
2. Defective 20 ft. retract switch 2. Replace 20 ft. retract switch (S33).
(S33).
continued
29-96 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
9. No or slow 20 FT. 4. Defective double-latching relay 4. Refer to Double-Pole, Double-

retract (Continued) (K16). Throw Latching Relays in the
6. Low pilot pressure. 6. Adjust pilot pressure.
7. Mis-adjusted B port relief valve in 7. Adjust B port relief valve and set
the expansion work section. nent Troubleshooting to trouble-
noid.
section.
12. One of the expansion cylinders 12. Refer to Correction 13. of Problem
(left) (S30). (S30).
noid.
section.
9. One of the side shift cylinders 9. Isolate and repack side shift cylin-
packing is defective. der. To isolate the defective cylin-
continued
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-97
10. No or slow side shift a. With the attachment fully side

(left) (Continued) shifted to the right, remove the
ton ends of both side shift cyl-
inders and plug them.
b. Depress the right side shift
tick.
piston end of the side shift cyl-
inders. If a flow of fluid is
(right) (S30). (S30).
noid.
section.
8. One of the side shift cylinders 8. Refer to Correction 8. of Problem
(out) (S28). (S28).
continued
29-98 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
12. No or slow slew left 5. Defective solenoid on the A port of 5. Refer to Solenoids in the Compo-
(out) (Continued) the left slew work section. nent Troubleshooting to trouble-
noid.
section.
a. Depress the left slew out micro
switch.
b. Observe the open port on the
9. The left slew cylinder packing is 9. Replace packing or cylinder.
defective.
(in) (S28). (S28).
noid.
section.
8. The left slew cylinder packing is 8. Refer to Correction 8. of Problem
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-99
right (out) (S29). (S29).
noid.
section.
9. The right slew cylinder packing is 9. To check the right slew cylinder,
a. With the attachment fully
slewed out (right side), remove
der and plug.
b. Depress the right slew out
tick.
right (in) (S29). (S29).
continued noid.
29-100 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
15. No or slow slew 6. Defective B port pilot cartridge on 6. Replace B port pilot cartridge.
right (in) the right slew work section.
(Continued)
section.
8. The right slew cylinder packing is 8. Refer to Correction 8. of Problem
slope right (if (S34). (S34).
equipped with pile
slope)
noid.
7. Defective pile slope work section. 7. Replace or repair slew work sec-
tion.
sloped left (the right pile slope
cylinders are fully extended
while the left pile slope cylin-
ders are fully retracted).
the left pile slope cylinders to
rod ends of the right pile slope
lic hoses.
c. Depress the pile slope left
continued stand.
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-101
16. No or slow pile d. Observe the open ports of the

slope right (if pile slope cylinders. If a flow
equipped with pile of fluid is detected from any
slope) cylinder, repack that defective
(Continued) cylinder.
slope left (if (S34). (S34).
equipped with pile
slope)
noid.
7. Defective pile slope work section. 7. Replace or repair right slew work
section.
sloped right (the right pile
retracted while the left pile
extended).
the right pile slope cylinders to
rod ends of the left pile slope
lic hoses.
continued
29-102 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
17. No or slow pile c. Depress the pile slope right

slope left (if switch (S34) on the control
equipped with pile stand.
slope)
(Continued) d. Observe the open ports of the
pile slope cylinders. If a flow
of fluid is detected from any
cylinder, repack that defective
cylinder.
18. Twistlocks drift 1. The twistlock cylinder packing is 1. Isolate and repack twistlock cylin-
defective. der. To isolate the defective cylin-
a. With the twistlocks fully
unlocked, remove the front cap
(located on the top side of the
twistlock cylinder) of the left
twistlock cylinder and the rear
cap of the right twistlock cylin-
der (located on the top side of
the twistlock cylinder).
b. Turn the twistlock override
switch on and depress the
unlock twistlocks micro switch
(S31) on the joystick.
left and right twistlock cylinder.
If a flow of fluid is detected
from either of the cylinders,
this is the bad cylinder and
requires repacking.
2. Defective twistlock work section. 2. Repair or replace twistlock work
section.
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-103
Illustration 29-67. Main Attachment Junction Box
06A-2458 SHT. 05
29-104 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
Illustration 29-68. Attachment Left End Junction Box
06A-2458 SHT. 12
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-105
Illustration 29-69. Attachment Right End Junction Box
06A-2458 SHT. 13
29-106 THDC
THDC/ THDCP
/ THDCP
- 954
- 954
/ 955
/ 955
/ 974
/ 974
/ 975
/ 975
(Rev.
(Rev.
06/03)
3/05)
1-12 RTGP-9042N (9/01)
Hoist Circuit

FOLDER ENVELOPES:
Illustration 29-70 - 06A2458 SHT. 15 (Corner Mounted
Proximity Switches ANSI Circuit)
Illustration 29-71 - 06Z0007 SHT. 03 (Frame Stops
ANSI Circuit)
THDC
THDC // THDCP
THDCP -- 954
954 // 955
955 // 974
974 // 975
975 (Rev.
(Rev. 3/05)
06/03) 29-107
Hoist Circuit
29-108 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Contents
Appendices
Page
SIRR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1
Leaf Chain Care, Maintenance, and Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . A-19
Welding Precautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-25
Torque Chart - Nuts and Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-27
Lubrication Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-31
Service Capacities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-37
Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-39
Fuel and Lubricant Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Section 1
Section Title
SIRR
Structural Inspection, Reporting, And Repair
For Powered Industrial Trucks
This document contains information of vital importance concerning the

inspection, reporting, and repair of fatigue cracks. If fatigue cracks are
not corrected they can lead to a catastrophic failure causing serious
injury to personnel and / or property.
It is important that the machine be inspected regularly. Any existing

fatigue cracks should be reported to the Taylor Machine Works, Inc.
engineering department immediately. Repairs must be made in
accordance with AWS methodologies.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-1

A-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)
These symbols are in accordance with AWS

A2.4-76, “Symbols for Non-Destructive Testing.”
Dangerous Action. Operating a powered indus-
trial truck without inspecting, identifying, and
Periodic inspection is
repairing fatigue cracks in the mast, carriage, required to detect fatigue cracks that have
attachment, steer axle, and frame weldments. grown to a significant size in order to avoid
serious failure of the structural weldment.
What Can Happen. If the fatigue crack is allowed
When a crack is found, the truck must be
to grow, catastrophic failure could occur in the
immediately taken out of service and repaired.
mast or other welded components causing serious
injury to personnel and / or property. Restoring the weld to its original condition by com-
How To Avoid The Danger. Follow the OSHA plete penetration welding is usually acceptable.
rules, 29 CFR, 1910.178 (q)(1), (5), & (7) which Sometimes this is not practical and a change in
require inspecting industrial trucks daily before geometry by means of cutting, grinding or adding
being placed in service, removing trucks from ser- additional material is more economical; however,
vice if cracks are found, and making repairs only the user must be cautioned that OSHA 29 CFR
as authorized by the manufacturer. If trucks are 1910.178 (a)(4) requires manufacturer’s prior
used on a round-the-clock basis, they shall be written approval for modifications and additions
examined after each shift. OSHA 29 CFR which affect capacity and safe operation.
1910.178 (p)(1) requires that trucks in need of Cracking may occur due to overloading, rough
repair be taken out of service. operation, poor yard conditions, severe duty
Structural Inspection and Reporting Proce- cycles, failing to keep lift chains properly adjusted,
dure. The information enclosed in this procedure improper shimming of mast rails, carrying the
is directed to the structural weldments of the truck loads too high or not properly centered, using
assembly. Areas that should be included for attachments that clamp the load to the forks, etc.
inspection on the front end of the truck are the If such cracking is found, a review of the operation
mast and carriage. Areas to be inspected on the should be made to see if any of the above listed
truck chassis include mast hangers, drive axle problems are occurring and if so, a change in the
mounts, A-frame connections, and steer axle operation should be made to avoid future prob-
mounts. lems. Some cracking may be due to geometry,
modifications or due to the attachments welded to
Inspection for Fatigue Cracks. Welded steel the structure. If this is the case, the geometry
structures always contain undetectable cracks, may have to be changed, the modification cor-
especially at welded joints. When these joints are rected, or the attachment changed or relocated to
subject to fluctuating stresses of sufficient magni- correct the cracking problem. OSHA requires that
tude, these cracks will grow. This is known as you have prior written approval of the manufac-
fatigue crack growth. No matter how low the turer for such changes.
stress levels are kept some fatigue crack growth
will occur in all welded structures. Test Procedures
Eventually, these fatigue cracks will become large 1. Visual (VT). Dirt and grease should be
enough to be detectable by nondestructive testing removed from the surface by wiping with a rag.
methods, i.e. VT, MT, DPT, or UT. One should look for cracked paint and rust
showing through the paint. Also, look for
Abbreviations. Basic Testing Symbols movement at bolted joints, irregular lines in
welds or dents, or deformations in the materi-
Type of Test Symbol al. Proper lighting is required in order to
Visual VT obtain satisfactory results.
Magnetic Particle MT 2. Magnetic Particle (MT). The test surface
Dye-Penetrant DPT must be free of loose rust, scale, moisture,
and painted surfaces must be cleaned at all
Ultrasonic UT points of electrode contact. Grinding, brush-
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-3

ing, or blasting do not affect results of this thereafter. These inspections should be per-
method of testing in most instances. formed by qualified maintenance personnel.
A magnetic field can be applied to the test NOTE: Duty cycles vary from extremely severe
material with: (capacity loads, high frequency of loading, rough
a. Permanent magnet. yards, etc.) to very light (partial capacities, few
b. Yoke which is an electromagnet type of load cycles, good yard conditions, etc.). Duty
device. cycle directly affects product life and maintenance
requirements. Depending on the quality and thor-
c. Passing high amperage current through
oughness of the daily inspections and the service
the part.
experience of the vehicle, the three-month visual
3. Dye-Penetrant (DPT). The test surface must inspection interval and the full-scale inspection
be thoroughly cleaned and dried. This can be interval may be adjusted (increased or decreased)
done with chemical solvents, vapor degreas- to levels appropriate for an individual vehicle duty
ing, or by mechanical methods. However, cycle.
cleaning mechanically, such as grinding, blast-
ing, or wire-brushing, might prove detrimental
to the test because surface discontinuities can

be masked by cold working of the surface. !
Therefore, mechanical cleaning methods must "
be kept to a minimum.
One of the following type penetrants should be Reporting Procedure. Taylor Machine Works,
used in conjunction with the proper procedure Inc. should receive reports of the results of any
to get satisfactory results: inspections.
a. Water soluble penetrant Photocopy a sketch from your maintenance manu-
b. Post emulsifiable penetrant al, make your own sketch, or photograph, and
show indication of crack if any are evident, stating
c. Solvent removable penetrant the following:
Follow the directions supplied with the dye-
penetrant for best results. 1. Location (right, left, inner, outer, machine side
etc.);
4. Ultrasonic (UT). Testing should be done in
accordance with AWS D1.1 approved meth- 2. Size of crack;
ods. 3. Extent of crack;
Frequency of Inspection. There are three (3) a. In toe of weld;
levels of inspection: b. Propagating into the base metal;
1. Daily. Mandatory daily examination of the c. Other description, etc.
truck as required by OSHA. (See Operator’s 4. Method of testing to detect cracks.
Guide and Safety Check for details.) This
examination is usually performed by the oper- If no cracks are found by yearly inspections,
ator (or other designated person). please confirm by a fax or a short letter.
2. Three-month inspection. A thorough visual Repair Procedure
inspection (VT) following the guidelines shown 1. Contact Taylor Machine Works, Inc.
in this procedure should be made every three
months (refer to sketches for details). These 2. If rewelding is suggested, use AWS approved
inspections should be performed by qualified welding procedures.
maintenance personnel. 3. If design modification is indicated, contact Tay-
3. 6,000 Hour Inspection. Full-scale inspection lor Machine Works, Inc. OSHA 29 CFR
(FS) including all examinations outlined in this 1910.178 (q)(5) requires that replacement
procedure (VT, MT, and DPT) should be made parts be equivalent as to safety with those
after the first year of operation and then every used in the original design. Different steel
two years or 6,000 hours, whichever is sooner, grades are used for different components. Dif-
A-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

ferent steel grades require different welding
procedures, pre-heatings, rods, etc.
Inspection Locations. Some weld points are
subject to higher stress levels than others. While
all welds should be inspected, particular attention
should be placed on the following representative
areas (see Illustrations). They are used as a ref-
erence for specific details, but do not necessarily
represent exact details used in the construction of
your truck.

The areas being inspected
must be properly cleaned prior to performing
the inspection. If not properly cleaned poten-
tially dangerous cracks may not be detected.

Never go under a raised mast,
carriage, forks or attachment unless proper
blocking has been securely placed to prevent
the mast, carriage, forks or attachment from
falling in event of hydraulic failure or drift.
Refer to the Safety Check booklet.
List of Illustrations
Illustration. 1. Inner and Outer Mast Arrangement . . A-6

Illustration. 2. Inner Mast Details 1 and 2 . . . . . . . . . . A-7
Illustration. 3. Outer Mast Details 3 and 4 . . . . . . . . . A-8
Illustration. 4. Carriage Details . . . . . . . . . . . . . . . . . . . A-9
Illustration. 5. Chassis Arrangement . . . . . . . . . . . . . A-10
Illustration. 6. Chassis Details 1 and 2 . . . . . . . . . . . A-11
Illustration. 7. Chassis Details 3 and 4 . . . . . . . . . . . A-12
Illustration. 8. Attachment Arrangement . . . . . . . . . . A-13
Illustration. 9. Attachment Detail 1 . . . . . . . . . . . . . . . A-14
Illustration. 10. Attachment Detail 2 . . . . . . . . . . . . . . A-15
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-5

Inner and Outer Mast Arrangement
Detail 1
Detail 3
Detail 4
Detail 2
Detail 5
Illustration 1. Inner and Outer Mast Arrangement
A-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Inner Mast Details
Detail 1
VT (3)
MT (FS)
Detail 2
VT (3)
MT (FS)
Illustration 2. Inner Mast Details 1 and 2
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-7

Outer Mast Details
VT (3)
MT (FS)
Detail 3
VT (3)
MT (FS)
VT (3)
MT (FS)
Detail 4
VT (3)
MT (FS)
VT (3)
MT (FS)
Detail 5
Illustration 3. Outer Mast Details 3 and 4
A-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Carriage Details
VT (3)
MT (FS)
Illustration 4. Carriage Details
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-9

Chassis Arrangement
Detail 2
Detail 4
Detail 3
Detail 1
Illustration 5. Chassis Arrangement
A-10 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Detail 1
VT (3)
MT (FS)
VT (3)
MT (FS)
Detail 2
Illustration 6. Chassis Details 1 and 2
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-11

Detail 3
VT (3)
MT (FS)
Detail 4
VT (3)
MT (FS)
Illustration 7. Chassis Details 3 and 4
A-12 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Attachment Arrangement
Detail 1
Detail 3
Detail 4
Detail 2
Detail 5
Illustration 8. Attachment Arrangement
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-13

Detail 1
VT (3)
MT (FS)
VT (3)
MT (FS)
Illustration 9. Attachment Wide Expansion Frame Detail 1
A-14 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Detail 2
VT (3)
Inspect these welds on the main frame.
MT (FS) Pay particular attention to the welds 5 feet
from the outside of the rail cap on both ends
of both top plates.
VT (3)
MT (FS)
VT (3)
MT (FS) VT (3)
VT (3)
MT (FS)
Inspect these welds on the wide expan- MT (FS)
sion frame. Pay particular attention to
the welds 1 foot on each side of the
supports pads and under the support
pads with the wide expansion frame in
both the 40 FT. and 20 FT. positions.
Illustration 10. Attachment Main Frame and Wide Expansion Frame Detail 2
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-15

Detail 3
VT (3)
MT (FS)
VT (3)
MT (FS)
Illustration 11. Attachment Slider Beam Detail 3
A-16 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Detail 4
VT (3)
MT (FS)
Illustration 12. Attachment Main Frame Detail 4
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-17

Detail 5
VT (3)
MT (FS)
VT (3)
MT (FS)
Inspect these welds on the narrow expansion frame. Pay
particular attention to the welds 1 foot on each side of the
supports pads and under the support pads with the narrow
expansion frame in both the 40 FT. and 20 FT. positions.
Illustration 13. Attachment Main Frame and Narrow Expansion Frame Detail 5
A-18 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Leaf Chain Care, Maintenance, and Replacement
The leaf chain (or chains) on your Taylor material handling equipment was selected based on thou-
sands of hours of safe operation over many years of fork lift trucks working in various types of material
handling operations.
The entire chain system, including chain anchors, anchor supports, bearings, and chain rollers, is
sized for the basic model capacity and load center shown on the serial plate.
The utility of fork lift truck type material handling equipment requires it to operate under a wide variety
of load conditions. These vary from a few low lifts to a very large number of high lifts per operating
hour.
The leaf chain is subjected to all the variations of environment, such as moisture, chemicals, tempera-
ture extremes, abrasives, and even salt water in some applications. The chain cannot have the bene-
fit of a protective coating (paint) and must depend on proper lubrication for combating the effect of
these conditions. The lubrication program greatly affects chain life.
The utility of the lift truck requires it to operate with a variety of attachments, such as forks, coil rams,
paper roll clamps, containers, marinas, and other attachments, all of which will place different dynamic
loads and load requirements on the hoist chains.
This wide variety of variables makes it impossible for Taylor to accurately predict an exact service life
of the leaf chain on the Taylor material handling equipment. Therefore, the following procedure of
inspection and replacement is recommended to avoid sudden failure.
Maintenance and Replacement of the Leaf Chain

In addition to the daily walk-around inspections, at each 500 hours of operation, the chain should be
thoroughly cleaned and inspected for elongation, pin rotation and protrusion, cracked plates, enlarged
holes, worn contour and worn surfaces on outside links or pin heads. If any of the above are ob-
served, replace the entire length of both chains. (Illustrations are on the following pages under
Modes of Chain Failure.)
Careful visual inspection of both inside and outside of the chain links where possible will reveal
some of these early indications of chain failure which may result in total chain breakage if left in ser-
vice.
NOTE: A hand-held mirror can aid tremendously in hard to see areas.
Particular attention should be given to that part of the chain which passes over the chain roller the
most frequently when under load.
It will be necessary to move the carriage to several locations and block it to prevent any possibility of
falling to gain the best possible visual access to the greatest number of pitches of chain.
After the chain is inspected and found to be serviceable, relubricate and place back in service.

Utilize proper safety precautions when blocking.
At 2,000 hours, disassemble the leaf chain from the vehicle. Thoroughly clean the chain and visu-
ally inspect for possible failure modes as listed for the 500 hour interval adding to that procedure the
following. Articulate each joint of the chain in both directions where the entire radius around each pin
can be inspected for cracks.
Particular attention should be given to that length of chain which passes over the rollers.
If the 2,000 hour inspection does not reveal any apparent excess wear or chain damage, relubricate
and install the chain in its original position on the machine.
At each 500 hours after the leaf chain is reinstalled, inspect and relubricate and follow the same pro-
cedure as on a new machine.
At 4,000 operating hours remove and discard the leaf chain and replace with a new and lubri-
cated chain.
Taylor’s recommendation to replace the chain at 4,000 hours is based on typical service duty cycles.
Experience in a specific application may allow this interval to be increased or may require that it be
decreased. Any change should be based on thorough inspection procedures outlined in this manual.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05) A-19

Modes of Chain Failure — See Illustrations on Page 3
1). Normal Wear – Chain Elongation. This is the result of wear when the load chain articu-
lates over the chain rollers. See illustration No. 1 for explanation of wear limits. When a
theoretical length of 12-in. new chain has elongated from wear to a length of 12.360-in.
(3%), it has exceeded the allowable wear limit. The wear should be measured in the
area that passes over the roller most often. If the length in the articulating section ex-
ceeds allowable wear limits (see text), replace entire length of both chains.
2). Chain Stretch. This can be caused by a combination of chain wear and overload. This
(overload) can show up as elongation of plates which do not pass over the rollers. If
there is any significant (1%) elongation in the area which does not pass over the rollers,
replace the entire length of both chains. Cracked chain plates (illustration no. 3) and en-
larged holes (illustration no. 7) can also result from chain stretch. The entire length of
both chains must be replaced if either of these conditions are found.
3). Plate / Pin Rotation and / or Plate / Pin Lateral Movement. This is generally caused
by the plate seizing the pin at articulation which indicates lack of lubrication where the
joint rotates over the roller. (See illustration No. 2.) This can result in pin breakage in
extreme cases. If any evidence of pin rotation is noted, replace entire length of both
chains.
4). Plate / Pin Cracks. Cracks result from fatigue, stress corrosion, corrosion fatigue. (See
illustrations No. 3, 4, and 5.) If any cracks are observed of any kind on any link, replace
entire length of chain.
5). Chain Joint Stiffness. (See illustration No. 6.) Lack of lubrication. Check the chain for
other modes of failure. If none are observed, lubricate thoroughly and place back in ser-
vice. If stiffness remains, the chain may have been damaged and require replacement.
6). Edge Wear of Plates. (See illustration No. 8.) Edge wear can occur at extended hours
of service and if sliding of chain occurs because of chain roller bearing problems. If wear
exceeds 5% of plate height of unused plate, replace entire length of chain.
7). Worn Outside Links or Pin Heads. (See illustration No. 9.) Check for misalignment of
the chain roller.
Replace the chain if wear is significant. Check (see Check Procedure) the chain for all
modes of failure. If none are found, eliminate the misalignment and place back into ser-
vice.
A-20 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05)

Modes of Chain Failure
Appearance and/or Symptom Probable Cause Correction

1. Excessive Length (elongation)
If chain gauge shows more than 12.3 Replace chain when it
inches per foot of elongation. reaches 12.3 inches per
Normal Wear foot.
Permanent deformation
(stretch) from overload Replace chain immediately
and eliminate the source
12.3”/FT. of overloads.
2. Abnormal Protrusion or Turned Pins
Excessive friction from high

loading and inadequate lubrica-
tion
Replace chain and
lubricate more frequently
3. Cracked Plates
(Fatigue)
Loading beyond chain’s capac-
ity (dropping load and catching Replace chain and eliminate
it) dynamic (impulse)
overloading
4. Arc-like Cracked Plates (Stress Severe rusting or exposure to

Corrosion) acidic or caustic medium, plus
static stress at press fit Replace chain and protect
between pin and plate. (No from hostile environment by
cyclic stress necessary) lubricating more frequently
5. Cracked Plates (Corrosion Fatigue)

Perpendicular to Pitch Line, plus rust
or other evidence of chemical
corrosion Corrosive environment and
cyclic motion (chain under Replace chain and protect
cyclic operation) from hostile environment by
lubricating more frequently
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05) A-21

Appearance and/or Symptom Probable Cause Correction
6. Tight Joints
Dirt or foreign substance
packed in joints
Clean and relube
Corrosion and rust Replace chain
Bent pins Replace chain
7. Enlarged Holes
High overload, dropping and

catching load Replace chain and correct
cause of overload
8. Worn Contour (Edge Wear) Replace chain when wear

reaches 5% of H.
Normal wear on sheave bearing
area
H Abnormal wear, rubbing on Replace chain and correct
roller cause of overload
5% of H Check chain roller bearing
9. Worn Surfaces on Outside Links

or Pin Heads
Misalignment, rubbing on roller

flanges Check alignment of
anchors, chain rollers
and chain roller pin.

I. Use proper safety precautions.
a. Always lower the mast and carriage to its lowest position before inspecting the leaf chain, un-
less the mast and carriage are securely blocked.
b. Always use OSHA approved support means (man lift, scaffolding, ladder, or platform) when
inspecting, removing, or servicing lift chains. Always turn off the engine. Do not allow anyone
to touch the controls while people are near the upright.
A-22 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05)

II. Use Lockout / Tagout Procedure to reduce causes of possible injury (refer to Lock-Out / Tag-Out
Procedure in the Safety Section found in the front of this manual).
III. Use only assembled chain. Do not build lengths from individual components.
IV. Do not attempt to rework damaged chains by replacing only the components obviously faulty. The
entire chain may be compromised and should be discarded.
V. Do not weld any chain or component. Welding spatter should never be allowed to come in contact
with chain or components.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05) A-23

Hoist Circuit
A-24 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05)

Appendix
Welding Precautions
Introduction. Once a crack is found in the truck Care and common sense are the best guides to
structure, it is advisable that you contact Taylor avoid such damage to the components.
Machine Works, Inc. for proper welding proce-
dures. Your truck is comprised of different metals,
each requiring its own unique repair procedure.
S Should any truck equipped with an APC
module require welding on its structural
Welding Precautions. Occasionally parts have
members, the RS connector must be
failed because of electric arc damage that
unplugged from the APC module prior to any
occurred during welding. This damage (starting
welding. Failure to comply with this caution
the failure), occurred when the current passed
may lead to damage to the APC module.
from the electrode through a pin, bearing, cylinder
piston or other moving part, seeking the ground. S Always connect the ground (closest to the
area to be welded, as possible, to provide
Shown on the illustration are some of the parts on the shortest path for welding current flow) to
the container handling truck subject to damage by the part or welded assembly that is to be
the passage of welding current. welded.
LIFT CHAIN
AND ROLLERS
SLEW
CYLINDERS
TILT CYLINDER ENDS
AND ALL INTERNAL
SUB-TROLLEY COMPONENTS
ROLLERS
WHEEL AND
SPINDLE
BEARINGS
EXPANSION
CYLINDERS
MAST & CARRIAGE

ROLLERS & PINS
AXLE BEARINGS UNIVERSAL ENGINE

TRANSMISSION
AND GEARS JOINT GEARS AND
GEARS AND STEER
BEARINGS BEARINGS
BEARINGS AXLE PIVOT
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-25

Hoist Circuit
A-26 THDC / THDCP - 954 /

955 / 974 / 975 (Rev.
06/03)
Torque Chart - Nuts and Bolts
Force - 100 lbs. Force - 200 lbs.

12” or 1’ 6” or 1/2’
Graphic Illustration
of Torque
Lever Arm or Wrench Handle Lever Arm or Wrench Handle
Torque - 100 ft-lbs. or 1200 in-lbs. Torque - 100 ft-lbs. or 1200 in-lbs.
NOTE: These charts are intended as a guide for the same SAE grade as the bolts on the chart.
the wrench torque that should be applied to tight- When nuts and bolts are of different grades, use
ening nuts and bolts, studs, or capscrews when the torque value for the lower of the two grades.
no torque is specified on the assembly print or
These charts are not intended for use in seating a
separate instructions. A steady pressure should
stud in a housing. The torque values, listed in the
be applied to the torque wrench until the torque
charts, are the maximum and minimum dry torque
value is obtained. A jerking action on the torque
values. To convert dry torque values to lubricated
wrench may not yield the proper torque value.
torque values, multiply the max. or min. dry torque
When tightening a bolt with a slotted nut, torque to value by 75% (.75). Lubricated is defined as oil-
the lower value shown on the applicable chart. coated bolts, LoctiteR coated bolts, plated bolts or
Then continue to tighten until the hole in the bolt bolts used with hardened flatwashers.
and the slot in the nut line up. Nuts must be of
Recommended Torque, Foot-pounds (ft-lbs)
SAE Grade 5 SAE Grade 8 12pt Ferry Head Capscrew
NF Threads Torque Torque Torque
1/4 - 28 9 - 10 13 - 14 15 - 17
5/16 - 24 17 - 19 23 - 25 31 - 34
3/8 - 24 32 - 35 45 - 50 59 - 65
7/16 - 20 50 - 55 72 - 80 92 - 102
1/2 - 20 81 - 90 108 - 120 135 - 150
9/16 - 18 108 - 120 153 - 170 NA
5/8 - 18 162 - 180 216 - 240 271 - 301
3/4 - 16 270 - 300 378 - 420 482 - 536
7/8 - 14 423 - 470 594 - 660 793 - 881
1 - 14 657 - 730 918 - 1020 1130 - 1255
1-1/8 - 12 792 - 880 1296 - 1440 NA
1-1/4 - 12 1116 - 1240 1800 - 2000 NA
1-3/8 - 12 1512 - 1680 2448 - 2720 NA
1-1/2 - 12 1980 - 2200 3200 - 3560 NA
NC Threads
1/4 - 20 7 - 8 11 - 12 14 - 15
5/16 - 18 15 - 17 23 - 25 28 - 31
3/8 - 16 28 - 31 41 - 45 52 - 58
7/16 - 14 45 - 50 63 - 70 83 - 92
1/2 - 13 68 - 75 99 - 110 120 - 133
9/16 - 12 99 - 110 135 - 150 NA
5/8 - 11 135 - 150 198 - 220 240 - 266
3/4 - 10 234 - 260 342 - 380 432 - 480
7/8 - 9 387 - 430 540 - 600 671 - 746
1-8 576 - 640 810 - 900 940 - 1044
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A- 27

SAE Grade 5 SAE Grade 8 12pt Ferry Head Capscrew
NF Threads Torque Torque Torque
1-1/8 - 7 720 - 800 1152 - 1280 NA
1-1/4 - 7 1008 - 1120 1638 - 1820 NA
1-3/8 - 6 1314 - 1460 2142 - 2380 NA
1-1/2 - 6 1746 - 1940 2844 - 3160 NA
Recommended Torque for Metric Bolts

Torque (ft-lbs)
Class 8.8 Classs 10.9
Bolt Size
(Equiv. to Grade 5) (Equiv. to Grade 8)
M6-1.00 7 - 8 10 - 11
M8-1.25 17 - 19 24 - 27
M10-1.50 33 - 37 48 - 53
M12-1.75 59 - 65 83 - 92
M16-2.00 144 - 160 207 - 230
M20-2.50 279 - 310 405 - 450
M24-3.00 486 - 540 690 - 775
M30-3.50 970 - 1078 1386 - 1540
Taylor Engineering Standards Recommended Torque for Countersunk

Flathead Bolts with Internal Hex Drive
Tightening procedure for countersunk flathead (these torque values applies only to hold caps
bolts with internal hex drive used for holding caps on tapered TimkenR bearings found on the
on tapered TimkenR bearings (found on the mast mast and carriage main roller assemblies)
and carriage main rollers):
Torque (ft-lbs)
1. The bolts and tapped holes must be clean and
B lt Si
Bolt Size
free of oil. (This can be done by using a spray Min. Max.
degreaser (Zep AerosolveR or equivalent) and
drying with compressed air.) 5/16 - 18 7.5 (90 in-lbs) 8.5 (102 in-lbs)
2. Apply LoctiteR to bolt threads. 3/8 - 16 14 (168 in-lbs) 16 (192 in-lbs)
3. Gradually tighten the bolts using a crossing 7/16 - 14 24 (288 in-lbs) 26 (312 in-lbs)
pattern. 1/2 - 13 38 (456 in-lbs) 42 (504 in-lbs)
4. Repeat Step 3 until bolts hold at least the mini- 5/8 - 11 74 81
mum torque value indicated in the torque chart
below. Stake head at three places with a cen- 3/4 - 10 135 150
ter punch.
5. When bearings are removed, it is necessary to
run a tap in the threaded holes and a die on
the bolts to remove LoctiteR residue. If a die
is not available, use new bolts.
A- 28 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05)

Torque Chart - Nuts and Bolts
Tightening procedure for Grade 8 countersunk

flathead bolts with internal hex drive used for
retaining the slide bearing block housings (found
on the mast and carriage):
1. Do Not use starwashers or any other type of
“locking” washer with grade 8 bolts.
2. Generously lubricate the head and threads of
the bolt with oil before installing.
3. Gradually tighten the bolts using a crossing
pattern until they hold at least the minimum
torque value as indicated in the torque chart
below.
4. In order to achieve torque values of this mag-
nitude, a high quality hex bit driver tool should
be used.
5. In order to minimize bending stresses in the
tool and thereby increase its life, the length of
the hex bit should be as short as possible
(e.g., Snap-OnR “Stubby” length).
Recommended Torque for Countersunk

Flathead Bolts with Internal Hex Drive
(these torque values applies only to those
bolts used to retain the slide bearing block
housings)
Torque (ft-lbs)
NC Threads
Th d H Bit
Hex Bi Size
Si
Min. Max.
5/16 - 18 3/16 13 15
3/8 - 16 7/32 20 22
7/16 - 14 1/4 30 32
1/2 - 13 5/16 65 70
5/8 - 11 3/8 110 115
3/4 - 10 1/2 265 270
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A- 29

Hoist Circuit
A- 30 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 1/05)

Lubrication
Introduction. The container handling truck has a Excess grease inside the mast rails may cause
large number of moving parts which operate under the rollers to slide when subjected to a heavy
extreme conditions. Frequent periodic lubrication load. If this happens, a flat spot will be worn
is absolutely essential to keeping the truck per- on the rollers and the rollers will continue to
forming satisfactorily with a minimum of downtime. slide until replaced with new rollers.
The illustrations in this section indicate the lubrica-
tion locations, intervals and type lubrication ser- NOTE: In severe environments, more frequent
vice to be performed. The Lube Chart Legend, lubrication service intervals of the inner and outer
located below Illustration 5, contains the type of mast main rollers may be required.
lubricant to be used for each symbol and the
abbreviation representation for each type of Lift Chains. The lift chains of the mast assembly
lubrication service. Refer, also, to the Preventive must be lubricated every 500 hours of operation
Maintenance chart for lubrication intervals and to (refer to Leaf Chain Care, Maintenance, and
the Fuel and Lubricant Specifications section Replacement section in the Appendices). Refer
for the types and weights of lubricants to be used to the Fuel and Lubricant Specifications for the
in different temperature ranges. type of lubricant to be used to lubricate the lift
chains.

Steer Axle Lubrication (See Illustration 5 for
S Always park the truck on level ground, apply steer axle lubrication)
the parking brake, shut down engine and
Lock Out & Tag Out truck before performing
When each side of the steer
lubrication. axle is lubricated, the truck must be steered to
S Do not climb on the mast assembly or on one side to access the grease fittings and
other high places of the truck while perform- Locked Out & Tagged Out.
ing lubrication.
S Always use OSHA approved ladders, stands,
or manlifts to reach high places on the truck.
S Do not use a material handling forklift as a
means to elevate personnel.
Chassis Lubrication (See Illustration 1 for chas-
sis lubrication)
Attachment Lubrication (See Illustration 2 for
attachment lubrication)
Carriage Lubrication (See Illustration 3 for car-
riage lubrication)
The carriage main roller

assemblies must not be over lubricated.
Excess grease inside the mast rails may cause
the rollers to slide when subjected to a heavy
load. If this happens, a flat spot will be worn
on the rollers and the rollers will continue to
slide until replaced with new rollers.
Mast Assembly Lubrication (See Illustration 4
for mast assembly lubrication)
The inner mast main roller

assemblies must not be over lubricated.
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-31

250 GR
DRIVE SHAFT
250 X
BRAKE
RESERVOIR
10 X
250 DR / CG
ENGINE
10 X
1000 DR
TRANSMISSION
250 X
3000 DR
DRIVE AXLE 10 X
3000 CG
HYDRAULIC
RESERVOIR
250 X
3000 DR
PLANETARY
HUBS
NOTE: Refer to the Lube Chart Legend for the type of lubri-
cant to be used. In addition, refer to the Fuel and Lubricant
Specifications for the types and weights of lubricants to be
used in different temperature ranges.
Illustration 1. Chassis Lubrication Points (See Lube Chart Legend for Lubrication Symbol Designation)
A-32 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

250 GR
250 GR PILE SLOPE
NARROW & WIDE CYLINDERS
EXPANSION FRAME (BOTH ENDS)
SLIDING SURFACES
250 GR
PILE SLOPE
TIE LINK EARS
(BOTH ENDS)
250 GR
HANGER CHAIN
LINK PLATES
250 GR
SUB-TROLLEY
ROLLERS
250 GR 250 GR
TWISTLOCK 250 GR
TWISTLOCK PILE SLOPE
BEARINGS GUIDE BLOCKS
PIVOT PINS
250 GR
EXPANSION
CYLINDERS
(PISTON END)
250 GR
SIDE SHIFT
NOTE: Refer to the Lube Chart Legend for the type of lubri- CYLINDERS
cant to be used. In addition, refer to the Fuel and Lubricant (PISTON END) 250 GR
Specifications for the types and weights of lubricants to be SIDE SHIFT
used in different temperature ranges. CYLINDER PINS
Illustration 2. Attachment Lubrication Points (See Lube Chart Legend for Lubrication Symbol Designation)
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-33

250 GR
SLEW CYLINDER
ANCHOR PINS
NOTE: Refer to the Lube Chart Legend for the type of lubri- 250 GR
cant to be used. In addition, refer to the Fuel and Lubricant CARRIAGE MAIN
Specifications for the types and weights of lubricants to be ROLLERS
Illustration 3. Carriage Lubrication Points (See Lube Chart Legend for Lubrication Symbol Designation)
A-34 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

1500 GR
CHAIN 500 GR
ROLLER LIFT CHAINS
PIN
OUTER MAST
250 GR
TILT
CYLINDER
EAR
INNER MAST
250 GR
MAST HANGER CLAMP
(LOCATED ON CHASSIS)
250 GR
INNER MAST
MAIN ROLLERS
NOTE: MAIN ROLLERS MUST BE ALIGNED WITH

GREASE HOLES LOCATED IN THE OUTER MAST
RAIL TO ACCESS GREASE FITTINGS.
NOTE: Refer to the Lube Chart Legend for the type of lubri-
cant to be used. In addition, refer to the Fuel and Lubricant
Illustration 4. Mast Lubrication Points (See Lube Chart Legend for Lubrication Symbol Designation)
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-35

GREASE RELIEF
250 GR
UPPER SPINDLE PIVOT
250 GR
STEER LINK
250 GR
PIVOT BLOCK
GREASE RELIEF
250 GR
LOWER PIVOT SPINDLE
NOTE: Refer to the Lube Chart Legend for the type of lubri- 3000 GR
cant to be used. In addition, refer to the Fuel and Lubricant WHEEL BEARING
Illustration 5. Steer Axle Lubrication Points (See Lube Chart Legend for Lubrication Symbol Designation)
SYMBOL LUBRICANT ABBREVIATIONS

ENGINE OIL, CF4 SAE 15W 40
HYDRAULIC FLUID C-4 TYPE with
X - Check Lubricant Level
FRICTION CONTROL MODIFIERS
DR - Drain and Refill
GEAR OIL, GL-5 OR MIL-2105D
GR - Grease
GREASE, CHEVRON ULTRA-DUTY OR EQUIVALENT
CG - Change
GREASE, CHEVRON ULTI-PLEX OR EQUIVALENT
VISTAC ISO 150 OR EQUIVALENT
LUBE CHART LEGEND
A-36 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

SERVICE CAPACITIES
Engine Lubrication
Cummins M11-C330 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 Quarts
Coolant System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Gallons
Fuel Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240 Gallons
Transmission
TC-36 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Quarts
TC-40 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Quarts
Drive Axle
Differential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 Quarts
Each Planetary Hub . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Quarts
Hydraulic Tank . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 Gallons
HYDRAULIC PRESSURE SETTINGS
Hydraulic Function Pressure Setting Set Pressure At

Lift 2900 psi High Idle
Tilt Back 2900 psi High Idle
Tilt Out 2500 psi High Idle
Steering 2500 psi High Idle
Main Attachment 2100 psi High Idle
Side Shift 2100 psi High Idle
Left Slew 2100 psi High Idle
Right Slew 2100 psi High Idle
Expand 1000 psi High Idle
Retract 2000 psi High Idle
Twistlocks 700 psi High Idle
Pile Slope 2100 psi High Idle
Pilot Minimum 175 psi Low Idle
Pilot Maximum 400 psi High Idle
THDC / THDCP – 954 / 955 / 974 / 975 (Rev. 3/05) A-37

Hoist Circuit
THD-180S – 360L (10/98) A-38

Preventive Maintenance
Service Symbols Service Intervals
A-Adjust C-Clean CG-Change Daily Or Monthly Or Six Months Or Yearly Or
10 Hours 250 Hours 1500 Hrs. 3000 Hrs.
D-Drain GR-Grease X-Check
POWER UNIT
ENGINE (Refer To The Engine Manufacturer’s Maintenance Manual For
Additional Requirements):
Hourmeter - check reading to determine when inspections are due X
Oil level-check for evidence of external leakage X
Oil change and filter element D / CG
Throttle control linkage X
Crankcase breather C
Clean engine C
Check engine mounts X
FUEL SYSTEM:
Fill fuel tank-check for leaks X
Fuel / water separator filters D
Fuel / water separator filter elements CG
Fuel tank, cap, hoses and clamps X
AIR INTAKE SYSTEM:
Check for leaks X
Air cleaner element filter indicator X
Air cleaner primary element (as conditions warrant) CG
Air cleaner safety element (or by filter indicator) CG
COOLING SYSTEM:
Coolant level and fan belts X
Hoses, clamps and radiator - check for leaks X
Radiator (clean externally as conditions warrant) X
Drain and flush cooling system (every 2 years or 6,000 hours)
Coolant filter (refer to the engine operation and maintenance manual for coolant filter
change interval)
ELECTRICAL SYSTEM:
Battery-check water level X
Alternator belts X
POWER TRANSFER
TRANSMISSION:
Maintain fluid level to full mark and check for leaks X
Clean transmission breather C
Drain and refill transmission (every 1000 hours)
Clean sump screen (every 1000 hours)
Transmission filter elements (every 500 hours)
DRIVE SHAFT:
Lubricate drive shaft, universal joints, slip joints and all other bearings. GR
AXLES
STEER AXLE - Visually inspect daily X
Lubricate all grease fittings on steer axle (refer to the Lubrication section in the
Appendices) GR
Repack wheel bearings GR
Check mounting bolts X
DRIVE AXLE - Visually inspect daily X
Differential and planetary hubs - maintain oil level X
Drain and refill differential and planetary hubs (refer to Fuel and Lubricant Specifications in
the Appendices for the type of gear oil to be used) D
Inspect brake linings X
Check mounting bolts X
BRAKE CONTROL SYSTEM
BRAKES:
Air tank (manual drain) D
Check air hoses and connections X
Fluid level in wet disc brake reservoir X
THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) A-39

Service Symbols Service Intervals
A-Adjust C-Clean CG-Change Daily Or Monthly Or Six Months Or Yearly Or
10 Hours 250 Hours 1500 Hrs. 3000 Hrs.
D-Drain GR-Grease X-Check
BRAKE CONTROL SYSTEM (Continued)
PARKING BRAKE:
Actuation X
Brake pads (replace as conditions warrant; refer to Section 15) X
Actuator adjustment (whenever the parking brake pads are replaced)
CHASSIS
Lubricate all grease fittings on machine not listed elsewhere. Use engine oil on linkage not
having grease fittings. GR
Mirrors and windows X/C
Access and anti-slip surfaces (clean) X/C
Audio-visual warning devices X
Handrails X
WHEEL EQUIPMENT:
Check tires, valve caps, wheels, lugs and tire pressure (refer to data plate on vehicle for
torque information) X
HYDRAULIC SYSTEM
HYDRAULIC PIPING AND RESERVOIR:
Maintain fluid level in hydraulic tank to full mark. X
Check piping for chafing, cracked hoses, loose fittings and leaks. X
Drain and refill entire hydraulic system and clean inside tank. CG / C
HYDRAULIC FILTERS:
Replace hydraulic tank breathers (as conditions warrant) CG
Hydraulic tank return filters CG
Hydraulic filter screens (suction strainers) C
Remote pilot hydraulic filter CG
HYDRAULIC VALVES:
Check for free operation X
HYDRAULICCYLINDERS:
Observe speed of movement - check for leaks X
ACCUMULATORS:
Check precharge X
ATTACHMENTS
MAST - Visually inspect daily X
Lubricate mast hinge clamps GR
Lubricate tilt cylinder ears and inner mast main rollers GR
Lubricate chain roller pins GR
Refer to Leaf Chain Care, Maintenance, and Replacement for additional
inspection requirements. X
Check all mast mounting hardware (mast hanger) X
CARRIAGE - Visually inspect daily X
Lubricate carriage main rollers and slew cylinder pins grease fittings GR
CONTAINER ATTACHMENT:
Check unit for loose parts and hydraulic leaks X
Lubricate the twistlock grease fittings, expansion cylinder end grease fittings, side shift
cylinder end grease fittings, pile slope cylinder ends, pile slope tie links, hanger chain link GR
plate grease fittings and sub-trolley roller grease fittings.
Lubricate the sliding surfaces of the expansion frames. (every 50 hours)
Visually inspect all twistlocks, guide blocks, interlocks and plungers. X
Check twistlocks and guide blocks ultrasonically or by magnaflux. Replace every 6000
hours. X
Visually inspect container attachment structure for cracks. X
Check hanger chain links for wear and flat spots. X
Check response of hydraulic functions. X
Check all container lights and safety devices. X
CAB
Check cab tilt and cab tilt cylinders for proper operation X
The service intervals for Preventative Maintenance are calculated based on normal operating conditions including ten hours
per day, fifty hours per week. If your operating conditions or duty cycles are more severe, the service should be conducted
more frequently, i.e. extremely dusty conditions may require more frequent servicing of the filters.
A-40 THDC / THDCP - 954 / 955 / 974 /RTGP-9040

975 (Rev. (12/95)
06/03)
CALIFORNIA
Proposition 65 Warning
Diesel engine exhaust and some of its constituents are known to

the State of California to cause cancer, birth defects, and other
reproductive harm.
Fuel and Lubricant Specifications
This replaces all previously published Fuel and Lubricant Specifications.

PRODUCT USED IN SPECIFICATIONS TEMPERATURE FACTORY FILLED
ENGINE Detroit Diesel API Classification CF2 Chevron Delo 400
OIL (2 Cycle) (SAE 15W 40 To Aid Starting) -25° F To 32° F Multi-grade
Heavy Duty
SAE 40 All Other Temps. Motor Oil
Detroit Diesel API Classification CE/SG or CF4 All Temperatures SAE 15W 40
(4-cycle) and Perkins SAE 15W 40
Cummins Diesels API Classification CE/SG or CF4
SAE 5W 30 -40° F to 68° F
SAE 10W 30 -10° F to 68° F
SAE 15W 40 -10° F to 115° F
Isuzu Diesels API Classification CE/SG
SAE 10W 30 -22° F To 90° F
SAE 15W 40 -10° F To 104° F
Gas & LP Engines API Classification CE/SG
SAE 5W 30 Below 60° F
SAE 15W 40 -10° F To 104° F
DIESEL All Diesel Engines ASTM Spec D-975 All Temperatures Chevron Diesel No. 2
FUEL No. 1 or No. 2, With Temp. Supressor
0.5% Sulfur Maximum Added November Thru
Centane Minimum 40 March
ANTI- Cooling System Maintain 50 - 50% Soft Water* Protection to -34° F Texaco 23 53
FREEZE Ethylene Glycol
(Low Silicate Antifreeze)
GM 6038-M or ASTM D3306
RUST Cooling System Any Reputable Manufacturer All Temperatures Included in Antifreeze
INHIBITOR Non-Chromate Only
TRANS- Automatic Transmission C-4 Type Fluid with Friction Control All Temperatures Chevron 1000 Tractor
MISSION Modifiers. Hydraulic Fluid
HYDRAU- Hydraulic System
LIC FLUID NOTE: Chevron 1000 Tractor Hydraulic
Fluid, Amoco 1000 and Mobil 424 have
WET DISC Wet Disc Brakes proven to be most effective in controlling
BRAKE wet disc brake noise.
COOLING
GEAR OIL Differentials Extreme Pressure Gear Oil Chevron Delo Gear
Planetary Hubs (GL-5 or MIL-2105D) 10° F Minimum Lubricant ESI 80W 90
Gear Boxes SAE 85W 140
SAE 80W 90 -15° F Minimum & Any
Higher Temperatures
BRAKE Hydraulic Brakes Specifications SAE J-1703 All Temperatures SAE J-1703
FLUID (Non-Petroleum Base)
Wet Disc Brake Actuator C-4 Type Fluid with Friction Control Mo- All Temperatures Chevron 1000 Tractor
difiers. See Hydraulic Fluid Above. Hydraulic Fluid
WHEEL All Timkenr Bearings Chevron Ulti-Plex** Grease Grade 1 below 0° F Chevron Ulti-Plex Grease
BEARINGS Which Use Grease NLGI Grades 1 & 2 or Equivalent Grade 2 above 0° F NLGI Grade 2
AND
SEALED
CHAIN
ROLLERS
GREASE All Other Grease Fittings Chevron Ultra Duty** Grease Grade 1 below 0° F Chevron Ultra Duty
FITTINGS EP NLGI 1, 2, or Equivalent Grade 2 above 0° F Grease EP NLGI 2
LEAF Vistacr ISO 150 Lubricant All Temperatures Vistacr ISO 150 Lubricant
CHAINS
* Soft Water - Cannot contain more than 300 parts per million hardness or 100 parts per million of either chloride or sulfide.
(See engine manual.)
**Grease recommendations are based on commercial products which have given satisfactory service. Users must be assured of similar per-
formance with products represented to be equivalent.
FL-1-4 (Rev. 7/02)

Aexq0071-02 (1) Bob Cat

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Maintenance Manual

THDC / THDCP - 954 / 955 / 974 /

D OPERATOR MUST BE TRAINED AND KNOWLEDGEABLE OF

TAYLOR MACHINE WORKS, INC.

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 7/05)

THE FOLLOWING ITEMS ARE NOT COVERED BY THIS WARRANTY:

TAYLOR MACHINE WORKS, INC.

Intro THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Important Safety Instructions 1. Use of hoisting devices not capable of

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) Safety-1

Safety-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Mounting and Dismounting:

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) Safety-3

Safety-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) Safety-5

Safety-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

HYDRAULIC TANK RADIATOR

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Air Intake System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Transmission Oil Cooler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9A

Brake Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Wet Disc Brakes Cooling System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15C

Air Dryer System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15D

Tires and Wheels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Heating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20H

Cab Tilt System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22D

Illustration 1-1. Cummins QSM11-C330 Engine Service Points

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-1

1-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

 Do not adjust belt tension to

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-3

1-4 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-5

1-6 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-7

1-8 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-9

1-10 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-11

5. Air compressor will 1. Air system leaks. 1. Refer to Correction 2. of Problem

6. Air compressor will 1. Air system leaks. 1. Refer to Correction 2. of Problem

7. Alternator not 1. Alternator belt is loose. 1. Check belt tension.

8. Coolant loss - 1. Coolant level is high. 1. Check coolant level.

8. Coolant loss - (continued) heater, hoses and con-

19. Engine runs rough 8. Contact a Cummins Authorized

21. Engine shuts off 9. Contact a Cummins Authorized

30. Fuel in coolant 2. Contact a Cummins Authorized

40. Excessive black 5. Contact a Cummins Authorized

1-26 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

1-30 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

PLACE THE FOLLOWING ILLUSTRATIONS IN

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 1-31

1-32 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

Illustration 2-1. Fuel System

THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03) 2-1

2-2 THDC / THDCP - 954 / 955 / 974 / 975 (Rev. 06/03)

FILLER CAP FUEL LEVEL

Illustration 2-3. Fuel Tank

Do not adjust belt tension to

9. Push the reset button on the top of the air

Do not use flammable liquids

Overfilling cells of the battery