Page 235 of 366

Engine Oil Additives
Do not add anything to your oil. The recommended oils
with the API service symbol are all you will need for
good performance and engine protection.
When to Change Engine Oil
Change engine oil and filter every 10,000 miles
(16 000 km) or every 12 months, whichever occurs first.
What to Do with Used Oil
Used engine oil contains certain elements that may be
unhealthy for your skin and could even cause cancer.
Do mot let used oil stay on your skin for very long. Clean
your skin and nails with soap and water, or a good
hand cleaner. Wash or properly throw away clothing or
rags containing used engine oil. See the manufacturer’s
warning about the use and disposal of oil products.
Used oil can be a threat to the environment. If you
change your own oil, be sure to drain all the oil from the
filter before disposal. Never dispose of oil by putting it
in the trash, pouring it on the ground, into sewers, or into
streams or bodies of water. Instead, recycle it by
taking it to a place that collects used oil. If you have a
problem properly disposing of your used oil, ask
your dealer, a service station or a local recycling center
for help.
5-29
Page 236 of 366
Engine Air Cleaner/Filter
The engine air cleaner/filter
is located in the center of
the engine compartment.
When to Inspect the Engine Air
Cleaner/Filter
If your vehicle has a filter
change indicator, inspect
the air cleaner/filter change
indicator at every oil
change and replace the
filter when the indicator
tells you to.
Vehicles without a change indicator, inspect the air
cleaner/filter at every oil change and replace at the first
oil change after 25,000 miles (40 000 km).
How to Inspect the Engine Air
Cleaner/Filter
Locate the filter change indicator. When the change
indicator turns black or is in the red/orange area, replace
the filter and reset the indicator.
5-30
Page 237 of 366

To inspect the air cleaner/filter, remove the filter from
the vehicle and lightly shake filter to release loose dust
and dirt. If the filter remains “caked” with dirt, a new
filter is required.
{CAUTION:
Operating the engine with the air cleaner/ lter
off can cause you or others to be burned. The
air cleaner not only cleans the air, it helps to
stop ame if the engine back res. If it is not
there and the engine back res, you could
be burned. Do not drive with it off, and be
careful working on the engine with the air
cleaner/ lter off.
Notice:If the air cleaner/ lter is off, a back re can
cause a damaging engine re. And, dirt can
easily get into your engine, which will damage it.
Always have the air cleaner/ lter in place when you
are driving.
Automatic Transmission Fluid
When to Check
A good time to have it checked is when the engine oil is
checked. See your Allison Automatic Transmission
Operator’s Manual to find out when to change your
transmission fluid and filters.
How to Check and What to Use
The Allison Automatic Transmission Operator’s Manual
that came with the vehicle shows how to check the
automatic transmission fluid and what fluid to use.
Automatic Transmission External Filter
Your automatic transmission filter requires periodic
replacement.
Consult the Allison Automatic Transmission Operator’s
Manual that came with the vehicle for proper change
intervals.
5-31
Page 238 of 366

Manual Transmission Fluid
Refer to the Maintenance Schedule to determine how
often to check the lubricant and when to change it. See
Scheduled Maintenance on page 6-5.
Refer to the Maintenance Schedule to determine what
kind of fluid to use. SeePart C: Recommended
Fluids and Lubricants on page 6-29.
When to Check
A good time to have it checked is when the engine oil is
checked. See your Maintenance Schedule to find out
when to change your transmission fluid.
How to Check and What to Use
Check the fluid level only when your engine is off, the
vehicle is parked on a level place and the transmission
is cool enough for you to rest your fingers on the
transmission case.
Then, follow these steps:
1. Remove the filler plug.
2. Check to be sure that the lubricant level is up to the
bottom of the fill opening. On heavy duty
transmissions (an inch of oil level equals about one
gallon of fluid.)
3. If the fluid level is good, install the plug and be sure
it is fully seated. If the fluid level is low, add more
fluid as described in the next steps.
How to Add Fluid
Here’s how to add fluid. Refer to the Maintenance
Schedule to determine the proper fluid to use. SeePart
C: Recommended Fluids and Lubricants on page 6-29.
1. Remove the filler plug.
2. Add fluid at the filler plug hole. Add only enough
fluid to bring the fluid level up to the bottom of the
fill opening.
3. Install the filler plug. Be sure the plug is fully
seated.
Engine Coolant (Gas and
DURAMAX™ engines)
If your vehicle has a Caterpillar®diesel engine, the
Caterpillar®Operation & Maintenance Manual provided
with your vehicle has information regarding the
proper coolant to use.
The cooling system in your vehicle is filled with
DEX-COOL
®engine coolant. This coolant is designed
to remain in your vehicle for 5 years or 150,000 miles
(240 000 km), whichever occurs first, if you add
only DEX-COOL
®extended life coolant.
5-32
Page 267 of 366

Rear Axle
When to Check and Change Lubricant
Refer to the Maintenance Schedule to determine
how often to check the lubricant and when to change it.
SeeScheduled Maintenance on page 6-5.
How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.
If the level is below the bottom of the filler plug hole,
you’ll need to add some lubricant. Add enough lubricant
to raise the level to the bottom of the filler plug hole.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. SeePart C: Recommended
Fluids and Lubricants on page 6-29.
Rear Axle Shift Motor
When to Check and Change Fluid
If you have an optional air-shift two-speed, controlled
traction, or locking differential type rear axle, a good time
to check the fluid level in the axle shift motor is when
the rear axle lubricant is checked. Use refrigerant
oil (shift motor only).
How to Check Fluid
Remove the plug on the front plate of the axle shift
motor, add enough fluid to raise the level to the bottom
of the filler plug hole, then replace the plug.
What to Use
Refer to your Maintenance Schedule to determine what
kind of lubricant to use. SeePart C: Recommended
Fluids and Lubricants on page 6-29.
5-61
Page 272 of 366

Secondary Fuel Filter and Water
Separator/Heater
If you have a Caterpillar®
diesel engine, you may
also have this spin-on filter
and fuel separator/heater.
It will be mounted in
the engine compartment
on the driver’s side of
the vehicle.
It has a metal drain bowl at the bottom. Occasionally,
check the bowl for any water or particles.
To check or drain the bowl, do the following:
•Shut off the engine.
•Push up on the spring loaded drain valve until clear
fuel is flowing from the valve.
The particles or water will drain out first. SeeEngine Oil
(Caterpillar
®Diesel Engine) on page 5-20orEngine
Oil (Gasoline Engine) on page 5-20orEngine Oil
(DURAMAX™ Diesel) on page 5-25for proper disposal
procedures.
Automatic Ether Injection System
If you have a Caterpillar®
diesel engine, you may
have this feature. The
ether cylinder is located in
the engine compartment
on the driver’s side of
the vehicle.
To change an empty ether cylinder, follow these steps.
1. Loosen the screw head on the cylinder-to-bracket
clamp.
2. Spread the clamp apart.
3. Clean any dirt from the neck of the cylinder and the
top of the valve before you take out the cylinder.
4. Check the inside of the valve for any foreign matter.
Clean the valve as necessary.
5. Cover the valve to protect it from dirt and take out
the cylinder.
5-66
Page 312 of 366

Maintenance Schedule
Introduction
Important: Keep engine oil at the proper level and
change as recommended.
Have you purchased the GM Protection Plan? The Plan
supplements your new vehicle warranties. See your
Warranty and Owner Assistance booklet or your dealer
for details.
Maintenance Requirements
Maintenance intervals, checks, inspections and
recommended fluids and lubricants as prescribed in this
manual are necessary to keep your vehicle in good
working condition. Any damage caused by failure
to follow scheduled maintenance may not be covered by
warranty.
Your Vehicle and the Environment
Proper vehicle maintenance not only helps to keep your
vehicle in good working condition, but also helps the
environment. Improper vehicle maintenance can
even affect the quality of the air we breathe. Improper
fluid levels or the wrong tire inflation can increase
the level of emissions from your vehicle. To help protect
our environment, and to keep your vehicle in good
condition, be sure to maintain your vehicle properly.
6-2
Page 315 of 366

Scheduled Maintenance
The services shown in this schedule up to 100,000 miles
(166 000 km) should be repeated after 100,000 miles
(166 000 km) at the same intervals for the life of
this vehicle. The services shown after 100,000 miles
(166 000 km) should be repeated at the same miles (km)
after those intervals for the life of this vehicle.
Gasoline engine vehicles have a computer that lets you
know when to change your engine oil. This is not
based on mileage, but on engine revolutions and engine
operating temperature. When the computer has
calculated that the oil needs changing, the GM Oil Life
System will indicate that a change is necessary.
The “Footnotes” at the end of this Maintenance
Schedule further explain maintenance services.
SeeService Publications Ordering Information on
page 7-7.
100 Miles (160 km)
❑Wheel stud nut service.(46)
1,000 Miles (1 600 km)
❑Wheel stud nut service.(46)
❑Rear axle air shift motor service.(11)
7,500 Miles (12 000 km)
❑Gasoline Engine Only: Check Oil Life System. If
engine oil and filter are changed, reset system. See
“Engine Oil (Gasoline Engine)” in the Index.(3) (9)
❑Check fluid levels (or every 3 months, whichever
occurs first).(1) (6)
❑Chassis lubrication service (or every 6 months,
whichever occurs first).(12)
❑Wheels and tires service.(15)
❑Hydraulic brake service (or every 6 months, whichever
occurs first).(7) (46)
❑Parking brake service (or every 6 months, whichever
occurs first).(8)
❑Air brake service (or every 6 months, whichever
occurs first).(39)
❑Air brake automatic slack adjuster service (or every
500 hours, whichever occurs first).(40)
❑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).(41)
❑Trailer brake hand control valve service (or every
3 months, or every 900 hours, whichever occurs
first).(42)
6-5