
(21)= Inspect parking brake drum and linings for wear
or cracks and check linkage and adjustment.
(22)= Wheel bearing service:
•Grease type — Clean, inspect, and lubricate with
the proper wheel bearing grease at designated
intervals or when hubs are removed. SeePart C:
Recommended Fluids and Lubricants on page 6-31.
•Oil-filled type — Some wheel bearings are
lubricated by axle lubricant. When you have oil-filled
hubs, use lubricant identical to that used in the
axle. Lubricant change intervals are the same for
front and rear axles. However, you must maintain
the proper oil level between change intervals.
SeeFront Wheel Bearings with Oil-Filled Hubs on
page 5-81andPart C: Recommended Fluids
and Lubricants on page 6-31.
(23)= Check the air intake system installation to see
that gaskets are seated properly and all hose
connections, fasteners, and other components are tight.
Tighten connections and fasteners or replace parts as
required.
(24)= Evaporative Control System Service, if equipped:
Check all fuel and vapor lines and hoses for proper
connections and correct routing (or every 24 months,
whichever occurs first). Replace parts as needed.(25)= Replace spark plugs. Inspect wires for damage.
Check the wire boot and boot heat shield fit at spark
plugs and coil. Replace parts as needed.
(26)= Check the fuel tank, fuel cap and fuel lines for
damage which could cause leakage. Inspect fuel cap for
correct sealing ability and any indications of damage.
Check fuel cap gasket for even filler neck imprint.
Replace parts as needed.
(27)= Check Exhaust Gas Recirculation (EGR) system
as described in the service manual. SeeService
Publications Ordering Information on page 7-10.
(28)= Inspect Electronic Vacuum Regulator Valve
(EVRV) filter for excessive contamination or plugging.
If needed, clean filter with solution of soap and water, let
dry and install.
(29)= Drain, flush, and refill cooling system. This
service can be complex; you should have your
dealer/retailer perform this service. SeePart C:
Recommended Fluids and Lubricants on page 6-31for
what to use. Inspect hoses. Clean radiator, condenser,
pressure cap, and neck. Pressure test cooling system
and pressure cap. For Caterpillar
®diesel engines,
always refer to the Caterpillar®Diesel Engine
Operation & Maintenance Manual for coolant
recommendations and change intervals.
6-23

(30)= Change the lubricant. SeePart C: Recommended
Fluids and Lubricants on page 6-31.
(31)= Front axle service: Re-pack upper kingpin roller
bearing.
(32)= Air brake service:
•Inspect brake lines and hoses for proper hook-up,
binding, leaks, cracks, chafing, etc. Inspect drum
brake linings for wear or cracks. Inspect other brake
parts at each wheel, including drums and wheel
speed sensor wiring. 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. Replace air
dryer cartridge only if excessive oil or moisture
is present. A small amount of oil in the system is
normal and should not be considered as a reason to
replace the cartridge.
•Test air lines for leaks; tighten as needed. Replace
compressor filter.
•Inspect air parking brake chamber for leaks and
damage. Inspect lines and hoses for leaks, cracks,
chafing, etc. Also check all attachments for tightness,
wear, or damage. Note: The spring brake section of
the rear brake diaphragms are non-serviceable.
•Replace the air compressor filter element, mounted
on the air compressor. For remote air compressor
intake service, refer to engine air cleaner filter
replacement.
•Remove, disassemble, clean, and inspect the safety
valve, service brake chambers, quick release valves,
quick release/double check valve combinations,
parking brake control valve, double check valves,
pressure protection valves, and ether injector
(if equipped).
•Remove, disassemble, and clean the application
valve; replace parts showing wear.
•Remove, disassemble, clean, and inspect the spring
brake control valve; replace rubber parts.
6-24

(33)= Clean and lubricate air brake automatic slack
adjuster. Check pushrod travel and auto adjustment
operation. Have serviced if needed.
(34)= Air brake chamber service: Check operation,
mounting clamps, and air lines and check for leaks.
(35)= Trailer brake hand control valve service: Check
operation; lubricate cam and follower.
(36)= Tighten the wheel stud nuts to the specified
torque values at 100 miles (160 km). Thereafter, tighten
them 1,000 miles (1 600 km) after each time the wheel
is removed. SeeTightening the Wheel Nuts on
page 5-86.
(37)= Inspect and clean any accumulated dirt, gravel,
or other foreign objects from the valves and valve boots
as needed. Using light oil, lubricate brake pedal to
brake application valve linkage components. Check any
rubber boots for cracks, holes, or deterioration and
replace if necessary.(38)= Estimated minimum. Actual mileage depends on
fuel and oil consumed.
(39)= If the vehicle has the Isuzu diesel engine and is
used primarily for long trip, highway service, change
the engine oil and filter every 18,000 miles (28 800 km),
or every 12 months, or every 750 hours of engine
operation, whichever occurs first.
(40)= Make sure any safety belt reminder light and
safety belt assemblies are working properly. Look
for any other loose or damaged safety belt system parts.
If you see anything that might keep a safety belt
system from doing its job, have it repaired. Have any
torn or frayed safety belts replaced.
6-25

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 the low air warning light or 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.
Engine Cooling System Service
Inspect the hoses and have them replaced if they are
cracked, swollen, or deteriorated. Inspect all pipes,
fittings, and clamps; replace as needed. Clean the
outside of the radiator and air conditioning condenser.
To help ensure proper operation, a pressure test of the
cooling system and pressure cap is recommended at
least once a year.
Exhaust System Inspection
Be alert for any changes in the sound of the exhaust
system or any smell of fumes. These are signs the
system may be leaking. Have it checked and/or repaired
at once. SeeEngine Exhaust on page 2-45and
Running the Vehicle While Parked on page 2-50.
Check to be sure that mud or dirt is not caked on the
exhaust system, especially in the area of the diesel
particulate filter and tailpipe. Clean the area as needed.
SeeDiesel Particulate Filter (Diesel Engine) on
page 2-46.
At high mileages, the DPF becomes loaded with ash.
This is normal. When the amount of ash loading is high,
see your dealer/retailer for DPF cleaning or replacement.
6-28

Usage Fluid/Lubricant
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.
Front Wheel
Bearings
(Except Oil
Filled Hubs)Wheel bearing lubricant meeting
requirements of NLGI #2,
Category GC or GC-LB
(GM Part No. U.S. 1051344, in
Canada 993037).
Front Wheel
Bearings with
Oil Filled HubsSAE 75W-90 Synthetic Axle
Lubricant for Medium Duty Trucks
(GM Part No. U.S. 89021675, in
Canada 10953512).
Transfer Case
(Four-Wheel
Drive)Manual Transmission Fluid
(GM Part No. U.S. 88861800, in
Canada 88861801).
Front Axle
(Four-Wheel
Drive)SAE 75W-90 Synthetic Axle
Lubricant for Medium Duty Trucks
(GM Part No. U.S. 89021675, in
Canada 10953512).
Usage Fluid/Lubricant
Rear Axle and
Rear HubsSAE 75W-90 Synthetic Axle
Lubricant for Medium Duty Trucks
(GM Part No. U.S. 89021675, in
Canada 10953512).
Rear Axle Shift
Motor LubricantRefrigerant Oil
(GM Part No. U.S. 5416939, in
Canada 10953496).
Propshafts and
SplinesWheel bearing lubricant meeting
requirements of NLGI #2, Category
GC or GC-LB
(GM Part No. U.S. 1051344, in
Canada 993037).
Cab — Door
Hinges and
LatchesMulti-Purpose Lubricant, Superlube
(GM Part No. U.S. 12346241, in
Canada 10953474).
Weatherstrip
ConditioningWeatherstrip Lubricant
(GM Part No. U.S. 3634770, in
Canada 10953518) or
Dielectric Silicone Grease
(GM Part No. U.S. 12345579, in
Canada 992887).
Weatherstrip
SqueaksSynthetic Grease with
Teflon, Superlube
(GM Part No. U.S. 12371287, in
Canada 10953437).
6-32

GM Mobility Reimbursement
Program
This program, available to qualified applicants, can
reimburse you up to $1,000 of the cost of eligible
aftermarket adaptive equipment required for your vehicle,
such as hand controls or a wheelchair/scooter lift.
The offer is available for a very limited period of time
from the date of vehicle purchase/lease. For more
details, or to determine your vehicle’s eligibility, visit
gmmobility.com or call the GM Mobility Assistance
Center at 1-800-323-9935. Text telephone (TTY) users,
call 1-800-833-9935.
General Motors of Canada also has a Mobility Program.
Call 1-800-GM-DRIVE (463-7483) for details. TTY
users call 1-800-263-3830.
Roadside Assistance Program
GM Medium Duty truck’s Roadside Assistance provides
stranded owner/operators with towing service for
disabled GM Medium Duty trucks, during the base
and/or engine warranty period, to the nearest authorized
GM Medium Duty dealer. This service combines the
efforts of trained telephone representatives with a
network of GM Medium Duty truck services.
Call GM Medium Duty truck’s Roadside Assistance at
1-800-862-4389 to reach a qualified representative who
can assist you in arranging a tow to the nearest GM
Medium Duty truck dealer when your vehicle is disabled.
We also provide dealer information at no charge,
such as location of the nearest authorized GM Medium
Duty truck dealer and their hours of operation.
Our Roadside Assistance is available 24 hours a day,
7 days a week, 365 days a year which includes
weekends and holidays. Should you have questions
about GM Medium Duty truck Roadside Assistance, call
the GM Medium Duty Roadside Assistance Center or
contact your dealer.
Canadian Roadside Assistance
Whenever a Medium Duty truck owned and operated in
Canada becomes disabled, the owner/operator should
contact the Canadian Roadside Assistance Center
at 1-800-268-6800 for assistance.
7-5

A
Accessories and Modifications............................ 5-4
Adding a Snow Plow or Similar Equipment.........4-23
Adding Equipment to Your Airbag-Equipped
Vehicle.......................................................1-59
Additives, Fuel................................................. 5-8
Add-On Electrical Equipment...........................5-102
Air Cleaner/Filter, Engine.................................5-39
Air Conditioning..............................................3-20
Air Pressure Gage..........................................3-46
Air Suspension...............................................2-44
Air Suspension Seats........................................ 1-6
Airbag
Off Light.....................................................3-29
Readiness Light..........................................3-28
Airbag System................................................1-48
What Will You See After an Airbag Inflates?....1-54
When Should an Airbag Inflate?....................1-52
Where Are the Airbags?...............................1-51
Airbag Systems
Adding Equipment to Your Airbag-Equipped
Vehicle...................................................1-59
Airbag Off Switch........................................1-56
How Does an Airbag Restrain?......................1-54
Servicing Your Airbag-Equipped Vehicle..........1-59
What Makes an Airbag Inflate?......................1-53
Antenna, Fixed Mast.......................................3-58Antilock Brake System (ABS)............................. 4-5
Antilock Brake, System Warning Light................3-34
Antilock Brakes, Trailer System Warning Light.....3-34
Appearance Care
Aluminum or Chrome-Plated Wheels..............5-98
Care of Safety Belts....................................5-96
Chemical Paint Spotting..............................5-100
Cleaning Exterior Lamps/Lenses....................5-97
Fabric/Carpet..............................................5-95
Finish Care.................................................5-97
Finish Damage............................................5-99
Instrument Panel, Vinyl, and Other Plastic
Surfaces.................................................5-96
Interior Cleaning..........................................5-94
Sheet Metal Damage...................................5-99
Tires..........................................................5-99
Underbody Maintenance.............................5-100
Vehicle Care/Appearance Materials...............5-100
Washing Your Vehicle...................................5-97
Weatherstrips..............................................5-96
Windshield and Wiper Blades........................5-98
Ashtray.........................................................3-20
Audio System.................................................3-47
Chime Level Adjustment...............................3-58
Fixed Mast Antenna.....................................3-58
Radio Reception..........................................3-58
Setting the Clock.........................................3-48
Theft-Deterrent Feature................................3-57
1

Cleaning
Aluminum or Chrome-Plated Wheels..............5-98
Exterior Lamps/Lenses.................................5-97
Fabric/Carpet..............................................5-95
Finish Care.................................................5-97
Instrument Panel, Vinyl, and Other Plastic
Surfaces.................................................5-96
Interior.......................................................5-94
Tires..........................................................5-99
Underbody Maintenance.............................5-100
Washing Your Vehicle...................................5-97
Weatherstrips..............................................5-96
Windshield and Wiper Blades........................5-98
Climate Control System...................................3-20
Outlet Adjustment........................................3-23
Rear Heating System...................................3-24
Clock, Setting.................................................3-48
Collision Damage Repair................................... 7-6
Control of a Vehicle.......................................... 4-3
Coolant
Engine Temperature Gage............................3-35
Heater, Engine............................................2-25
Low Warning Light.......................................3-35
Surge Tank Pressure Cap.............................5-47
Cooling System..............................................5-50
Cruise Control................................................3-10
Customer Assistance Information
Customer Assistance for Text
Telephone (TTY) Users............................... 7-3
Customer Assistance Offices........................... 7-4Customer Assistance Information (cont.)
Customer Satisfaction Procedure..................... 7-2
GM Mobility Reimbursement Program............... 7-5
Reporting Safety Defects to General Motors...... 7-9
Reporting Safety Defects to the Canadian
Government.............................................. 7-9
Reporting Safety Defects to the United
States Government.................................... 7-9
Roadside Assistance Program......................... 7-5
Service Publications Ordering Information........7-10
D
Daytime Running Lamps..................................3-15
Daytime Running Lamps Indicator Light.............3-41
Defensive Driving............................................. 4-2
Diesel
Running Out of Fuel....................................2-50
Diesel Engine.................................................2-26
Engine Alarm and Automatic Shutdown...........2-18
Exhaust Restrictor.......................................2-22
Fuel............................................................ 5-9
High Idle System.........................................2-20
Starting......................................................2-14
Diesel Particulate Filter....................................2-46
Diesel Particulate Filter Warning Light................3-45
Differential Lock Control, Rear Axle..................... 4-7
Differential Lock Indicator Light.........................3-40
Doing Your Own Service Work........................... 5-6
3