2002 GMC ENVOY transfer case maintenance

4-59
CAUTION:
It can be dangerous to get out of your vehicle if
the shift lever is not fully in PARK (P) with the
parking brake firmly set. Your vehicle can roll.
If you have left the engine running, the vehicle
can move suddenly. You or others could be
injured. To be sure your vehicle won't move, even
when you're on fairly level ground, use the steps
that follow.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set.
If the transfer case on four-wheel drive vehicles is
in NEUTRAL, your vehicle will be free to roll,
even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-- not
in NEUTRAL. See ªFour
-Wheel Drive
(Automatic Transfer Case)º in the Index.
When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:

start your engine,

shift into a gear, and

release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.
Maintenance When Trailer Towing
Your vehicle will need service more often when you're
pulling a trailer. See the Maintenance Schedule for more
on this. Things that are especially important in trailer
operation are automatic transmission fluid (don't
overfill), engine oil, axle lubricant, belt, cooling system
and brake system. Each of these is covered in this
manual, and the Index will help you find them quickly.
If you're trailering, it's a good idea to review these
sections before you start your trip.
Check periodically to see that all hitch nuts and bolts
are tight.

6-21 How to Check Lubricant
To get an accurate reading, the vehicle should be on a
level surface.
The proper level is from 0 to 3/8 inch (0 to 10 mm)
below the bottom of the filler plug hole.
What to Use
Refer to the Maintenance Schedule to determine what
kind of lubricant to use. See ªRecommended Fluids and
Lubricantsº in the Index.
Four-Wheel Drive
Lubricant checks in this section also apply to these
vehicles. However, there are two additional systems that
need lubrication.
Transfer Case
When to Check Lubricant
Refer to the Maintenance Schedule to determine how
often to check the lubricant. See ªPeriodic Maintenance
Inspectionsº in the Index.

Scheduled Maintenance
7-11
50,000 Miles (83 000 km)

Change automatic transmission fluid and filter if the vehicle is mainly driven
under one or more of these conditions:
± In heavy city traffic where the outside temperature regularly reaches 90
F
(32
C) or higher.
± In hilly or mountainous terrain.
± When doing frequent trailer towing.
± Uses such as found in taxi, police or delivery service.
If you do not use your vehicle under any of these conditions, change the fluid
and filter at 100,000 miles (166 000 km).
Automatic Transfer Case Only: Change transfer case fluid.
52,500 Miles (87 500 km)
Check rear/front axle fluid level and add fluid as needed. Check constant
velocity joints and axle seals for leaking.
Rotate tires. See ªTire Inspection and Rotationº in the Index for proper
rotation pattern and additional information. (See footnote +.)
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Scheduled Maintenance
7-14
100,000 Miles (166 000 km)

Replace spark plugs.
An Emission Control Service.

Change automatic transmission fluid and filter if the vehicle is mainly driven
under one or more of these conditions:
± In heavy city traffic where the outside temperature regularly reaches 90
F
(32
C) or higher.
± In hilly or mountainous terrain.
± When doing frequent trailer towing.
± Uses such as found in taxi, police or delivery service.
If you haven't used your vehicle under severe service conditions listed
previously and, therefore, haven't changed your automatic transmission fluid,
change both the fluid and filter.
Automatic Transfer Case Only: Change transfer case fluid.
150,000 Miles (240 000 km)
Drain, flush and refill cooling system (or every 60 months since last service,
whichever occurs first). See ªEngine Coolantº in the Index for what to use.
Inspect hoses. Clean radiator, condenser, pressure cap and neck. Pressure test
the cooling system and pressure cap.
An Emission Control Service.
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8-12
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.
Owner's Information
Owner publications are written specifically for owners
and intended to provide basic operational information
about the vehicle. The owner's manual will include the
Maintenance Schedule for all models.
Current and Past Model Order Forms
Service Publications are available for current and
past model GM vehicles. To request an order form,
please specify year and model name of the vehicle.
ORDER TOLL FREE: 1-800-551-4123Visit Helm, Inc. on the World Wide Web at: www.helminc.com
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