
❑Cooling system service. Clean the cooling
system filler cap with clean water, clean
the core, pressure test the cap and the
system for proper pressure capability, and
inspect condition of cooling and heater
hoses and clamps. Replace hoses if cracked,
swollen, or damaged.
❑Replace fuel filter(s) (or every 12 months,
whichever occurs first).(2)
❑Steering system service.(12)
❑Front and rear suspension service.(13)
❑Spring-to-axle U-bolts and shackle bolts
service.(15)
❑Exhaust system service (or every 6 months,
whichever occurs first).(2) (3) (16)
❑Inspect door hinge pins and bushings and
replace as necessary.
❑Wheel bearing (grease type) service (and
whenever hubs are removed).(22) (36)
❑Wheels and tires service.(14)
❑Hydraulic brake service (or every 6 months,
whichever occurs first).(6) (36)
❑Parking brake service (or every 6 months,
whichever occurs first).(21)❑Air brake service (or every 6 months, whichever
occurs first).(32)
❑Air brake automatic slack adjuster service (or
every 500 hours, whichever occurs first).(33)
❑Check air brake relay valve operation and check
for leaks (or every month, or every 300 hours,
whichever occurs first).
❑Clean air brake application valve (or every
3 months, or every 300 hours, whichever
occurs first). Lubricate linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(34)
❑Air brake system valve service (or every
3 months, or every 900 hours, whichever
occurs first).(37)
❑C600, C700, and C800 Gasoline Engines
Only: Engine drive belts service (or every
12 months, whichever occurs first).(17)
❑Thermostatically controlled engine cooling
fan service.(3) (19)
❑Shields and underhood insulation
service.(3) (4) (20)
❑Rear axle air shift motor service.(10)
380

❑Clean air brake application valve (or every
3 months, or every 300 hours, whichever
occurs first). Lubricate linkage.
❑Air brake chamber service (or every 2 months,
whichever occurs first).(34)
100,000 Miles (160 000 km)
❑Diesel Only: Inspect engine drive belt;
replace as necessary.
❑Gasoline Engine Only (Vehicles with
GVW of 16,000 lbs or less): Spark plug
service.(2) (25)
❑Change power steering fluid (or every
36 months, whichever occurs first).(12)
❑Replace power steering reservoir filter element
(or every 24 months, whichever occurs first).
❑Wheel bearing (oil type) service (and whenever
hubs are removed).(22) (36)
❑Except four-wheel drive: Front axle service.(31)
❑Four-wheel drive only: Front axle service.(30)
❑Four-wheel drive only: Transfer case
service.(30)
❑Rear axle service — Eaton
®, Rockwell®,
Spicer®axles (or every 12 months, whichever
occurs first).(30)❑Exhaust brake service, if equipped. Check for
excessive spindle free play and smooth
operation. Lubricate ball joint cap.
❑Inspect air compressor discharge port (or every
6 months or every 1,800 hours, whichever
occurs first).
❑Manual transmission (ZF 6-speed only) fluid
replacement (or every 48 months, whichever
occurs first).
❑Trailer brake hand control valve service (or every
12 months, or every 3,600 hours, whichever
occurs first).(35)
120,000 Miles (192 000 km)
❑C600, C700, and C800 Gasoline Engines Only:
Replace engine drive belts.
❑C400 and C500 Gasoline Engines Only: Engine
drive belts service (or every 12 months,
whichever occurs first).(17)
150,000 Miles (240 000 km)
❑Cooling system service (or every 60 months
since last service, whichever occurs
first).(2) (29)
❑Diesel Engine Only: Inspect engine drive belt;
replace as necessary.
382

(2)= An Emission Control Service.
(3)= A Noise Emission Control Device.
(4)= Applies to vehicles sold in the United States
and is recommended for vehicles sold in Canada.
(5)= Check fluid level in brake master cylinder,
power steering pump, front and rear axles,
transmission, and hydraulic spring parking brake
pump (if equipped). A low fluid level in the
brake master cylinder can indicate worn brake
linings and should be checked accordingly.
(6)= Inspect brake lines and hoses for proper
hook-up, binding, leaks, cracks, chafing, etc.
Inspect disc brake pads for wear and rotors for
surface condition. Inspect caliper assemblies.
Check brake pedal for excessive free play or
travel (or every 6 months, whichever occurs first)
and have serviced if needed. Check brakes
more often if driving habits and conditions result
in frequent braking.(7)= This vehicle has the Engine Oil Life System.
This system will show you when to change the
engine oil and filter — usually between 3,000 miles
(5 000 km) and 12,000 miles (20 000 km) since
your last oil change. Under severe conditions,
the indicator may come on before 3,000 miles
(5 000 km). Never drive your 7.8L diesel engine
vehicle more than 12,000 miles (20 000 km),
or 12 months, or 600 engine hours, without an
oil and filter change.
Remember to reset the Engine Oil Life System
whenever the oil is changed. For more information,
seeEngine Oil Life System (Gasoline Engine)
on page 276orEngine Oil Life System
(DURAMAX
®Diesel) on page 278orEngine
Oil Life System (Caterpillar®Diesel Engine)
on page 279.
384

(11)= Chassis Lubrication Service: Lubricate all
grease fittings in front suspension, front axle,
and steering linkage. DO NOT lubricate kingpin
bushings with air pressure equipment; instead,
use a hand grease gun to ensure complete purge
and eliminate sealer cap distortion. Front axle
tie rod ends, both upper and lower kingpin fittings,
and both steering linkage relay rod ends should
be greased with the vehicle loaded on the ground
and wheels turned straight ahead, NOT with
the vehicle on a hoist. Apply kingpin bushing
lubricant to both upper and lower kingpin grease
fittings until new lubricant purges from between
the upper shim pack and thrust bearing. Lubricate
transmission and shift linkage, hood latches
and hood hinges, parking brake lever pivot, clevis
pins and linkage, disc brake caliper rails, clutch
linkage and release bearing (if equipped), bearing
pads, propshaft universal joints, brake camshaft
bracket, slack adjusters, pedal shaft, clutch
cross shaft, clutch pedal springs, and clutch cable
bushing at transmission. Lubricate suspension,
axle, and steering linkage more often when
operating under dusty or muddy conditions and in
excessive off-road use. Frequently power-washed
vehicles will require more frequent lubrication.(12)= Check steering system:
•Look for damaged, loose, or missing parts.
Inspect the steering linkage relay rod and
tie rod ends for looseness or lack of lubricant.
Also look for parts showing signs of wear
or lack of lubrication. Replace parts as
needed. Also check steering gear mounting
bolts, pitman arm nut, gear housing upper
cover and side cover attaching bolts, steering
column mounting bolts and cardan joint
clamp bolts; tighten if necessary. See the
service manual.
•Inspect power steering hoses, tubes, and
fittings for leaks. Hoses and lines must not
be twisted, kinked, or tightly bent. Make sure
clips, clamps, supporting tubes, and hoses
are in place and properly secured.
•Check steering gear for leakage around
pitman shaft and housing. If leakage is evident
(lubricant oozing out, not just oily film), leak
should be corrected immediately.
386

Starter Switch Check
{CAUTION:
When you are doing this inspection, the
vehicle could move suddenly. If the vehicle
moves, you or others could be injured.
1. Before you start, be sure you have enough
room around the vehicle.
2. Firmly apply both the parking brake and the
regular brakes.
Do not use the accelerator pedal, and be ready
to turn off the engine immediately if it starts.
3. On automatic transmission vehicles, try to
start the engine in each gear. The starter
should work only in PARK (P), if equipped,
or NEUTRAL (N). If the starter works in
any other position, your vehicle needs service.
On manual transmission vehicles, the starter
should work only when the clutch pedal is
all the way down.
Automatic Transmission Shift
Indicator Check
Check that the indicator points to the gear chosen.
Steering Check
Be alert for any changes in steering action,
abnormal front tire wear or steering wheel position.
An inspection or service is needed when the
steering wheel is harder to turn or has too much
free play, or if there are strange sounds when
turning or parking.
Brake System Check
Be alert to illumination of the low air warning lamp
or for the tone alarm, or changes in braking
action, such as repeated pulling to one side,
unusual sounds when braking or increased
brake pedal travel. Make sure air brake system
reservoirs are drained daily with full system
air pressure, and check system for leaks.
Any of these conditions could indicate the need
for brake system inspection and/or service.
393

Usage Fluid/Lubricant
Engine Coolant
(Gasoline
Engine &
DURAMAX
®/
Isuzu Diesel)50/50 mixture of clean, drinkable
water and use only DEX-COOL
®
Coolant. SeeEngine Coolant (Gas
and DURAMAX®/Isuzu Engines)
on page 284orEngine Coolant
(Caterpillar
®Diesel Engines)
on page 287.
Hydraulic Brake
SystemDelco
®Supreme 11 Brake Fluid
or equivalent DOT-3 brake fluid.
Windshield
Washer SolventGM Optikleen
®Washer Solvent.
Clutch Bearing
LubricantClutch Bearing Lubricant
(GM Part No. 12378484 or
equivalent NLGI #3 consistency).
Exhaust Brake
Ball Joint Cap
LubricantHigh-Temperature Grease
(GM Part No. U.S. 1051344,
in Canada 903037) or
NLGI #3 consistency.
Usage Fluid/Lubricant
Power Steering
SystemDEXRON
®-VI Automatic
Transmission Fluid.
Manual
TransmissionSynthetic Manual Transmission
Fluid (GM Part No. U.S. 12345724,
in Canada 10953510).
Automatic
TransmissionSee the Allison Transmission
®
Operator’s Manual for correct
transmission fluid.
Key Lock
CylindersMulti-Purpose Lubricant, Superlube
(GM Part No. U.S. 12346241,
in Canada 10953474).
Chassis
LubricationChassis Lubricant
(GM Part No. U.S. 12377985,
in Canada 88901242) or lubricant
meeting requirements of NLGI #2,
Category LB or GC-LB.
398

Reporting Safety Defects to
General Motors
In addition to notifying NHTSA (or Transport
Canada) in a situation like this, we certainly hope
you’ll notify us. Please call us at 1-800-862-4389,
or write:
GM Medium Duty Truck
Customer Assistance Center
P.O. Box 44947
Detroit, MI 48244
In Canada, please call us at 1-800-263-3777
(English) or 1-800-263-7854 (French). Or, write:
General Motors of Canada Limited
Customer Communication Centre, CA1-163-005
1908 Colonel Sam Drive
Oshawa, Ontario L1H 8P7
Service Publications Ordering
Information
Service Manuals
Service Manuals have the diagnosis and repair
information on engines, transmission, axle
suspension, brakes, electrical, steering, body, etc.
Transmission, Transaxle, Transfer
Case Unit Repair Manual
This manual provides information on unit
repair service procedures, adjustments, and
specifications for GM transmissions, transaxles,
and transfer cases.
Service Bulletins
Service Bulletins give technical service
information needed to knowledgeably service
General Motors cars and trucks. Each bulletin
contains instructions to assist in the diagnosis
and service of your vehicle.
In Canada, the service bulletin reference number
can be obtained by contacting your General
Motors dealer or by calling 1-800-GM-DRIVE
(1-800-463-7483). This reference number is
needed to order the service bulletin
from Helm, Inc.
RETAIL SELL PRICE: $6.00 US +
Processing Fee
415

Flashers, Hazard Warning........................... 142
Flat Tire...................................................... 330
Fluid
Automatic Transmission............................ 282
Manual Transmission................................ 283
Power Steering........................................ 295
Windshield Washer.................................. 296
Four-Wheel Drive...............................119, 312
Front Axle................................................... 313
Front Wheel Bearings with Oil-Filled Hubs ... 319
Fuel............................................................ 251
Additives.................................................. 252
Diesel Engine Fuel................................... 253
Filling a Portable Fuel Container.............. 266
Filling Your Tank...................................... 264
Filter........................................................ 317
Filter Replacement................................... 263
Fuels in Foreign Countries....................... 264
Gage....................................................... 181
Gasoline Octane...................................... 251
Gasoline Specifications............................ 251
Primary Filter and Water Separator.......... 317
Running Out of Fuel................................ 262
Secondary Filter and Water Separator/
Heater.................................................. 318
Very Cold Weather Operation................... 256
Water in Fuel........................................... 256Fuel (cont.)
Water in Warning Light............................ 182
What Fuel to Use.................................... 253
Fuses
Fuses and Circuit Breakers...................... 341
Instrument Panel Fuse Block................... 342
Underhood Fuse Block............................. 344
Windshield Wiper..................................... 341
G
Gage
Air Pressure............................................. 183
Check Gages Warning Light..................... 180
Engine Coolant Temperature.................... 173
Filter Minder............................................ 182
Fuel......................................................... 181
Hourmeter................................................ 183
Oil Pressure............................................. 175
Speedometer........................................... 163
Tachometer.............................................. 163
Transmission Temperature........................ 178
Voltmeter Gage........................................ 168
Gasoline
Octane..................................................... 251
Specifications........................................... 251
Gasoline Engine, Starting.............................. 97
GM Mobility Reimbursement Program.......... 407
422