2002 GMC ENVOY 4WD

2-27
Automatic Transfer Case (If Equipped)
If your vehicle is equipped
with the automatic transfer
case, the transfer case knob
is located to the right of the
steering wheel on the
instrument panel. Use this
knob to shift into and out of
four
-wheel drive.You can choose among four driving settings:
2HI: This setting is for driving in most street and
highway situations. Your front axle is not engaged in
two
-wheel drive. It also provides the best fuel economy.
A4WD: This setting is ideal for use when road
conditions are variable. When driving your vehicle in
A4WD, the front axle is engaged, but the vehicle's
power is sent to the rear wheels. When the vehicle
senses a loss of traction, the system will automatically
engage four
-wheel drive. Driving in this mode results in
slightly lower fuel economy than 2HI.

2-28
4HI: Use 4HI when you need extra traction, such as
on snowy or icy roads or in most off
-road situations.
This setting also engages your front axle to help drive
your vehicle.
4LO: This setting also engages your front axle and
delivers extra torque. You may never need 4LO. It sends
maximum power to all four wheels. You might choose
4LO if you are driving off
-road in deep sand, deep mud,
and climbing or descending steep hills.
CAUTION:
Shifting the transfer case to NEUTRAL can
cause your vehicle to roll even if the transmission
is in PARK (P). You or someone else could be
seriously injured. Be sure to set the parking
brake before placing the transfer case in
NEUTRAL. See ªParking Brakeº in the Index.
NEUTRAL: Shift the vehicle's transfer case
to NEUTRAL only when towing your vehicle.
See ªRecreational Vehicle Towingº in the Index
for more information.
An indicator light in the knob will show you which
position the transfer case is in. The indicator lights will
come on briefly when you turn on the ignition and one
will stay on. If the lights do not come on, you should
take your vehicle to your dealer for service. An indicator
light will flash while shifting the transfer case. It will
remain illuminated when the shift is complete. If for
some reason the transfer case cannot make a requested
shift, it will return to the last chosen setting.
If the SERVICE 4WD light on the instrument panel
cluster stays on, you should take your vehicle to your
dealer for service. See ªService 4WDº in the Index for
further information.

2-29
Shifting to 4HI or A4WD
Turn the knob to 4HI or A4WD. This can be done at any
speed and the indicator light will flash while shifting. It
will remain illuminated when the shift is complete.
Shifting to 2HI
Turn the knob to 2HI. This can be done at any speed.
Shifting to 4LO
To shift to 4LO, the vehicle's engine must be running and
the vehicle must be stopped or moving less than 2 mph
(3.2 km/h) with the transmission in NEUTRAL (N). The
preferred method for shifting into 4LO is to have your
vehicle moving 1 or 2 mph (1.6 to 3.2 km/h). Turn the
knob to 4LO. You must wait for the 4LO indicator light
to stop flashing and remain illuminated before shifting
your transmission into gear.
If you knob to 4LO when your vehicle is in gear
and/or moving, the 4LO indicator light will flash for
30 seconds and not complete the shift unless your
vehicle is moving less than 2 mph (3.2 km/h) and the
transmission is in NEUTRAL (N). After 30 seconds,
the transfer case will return to the setting last chosen.Shifting Out of 4LO
To shift from 4LO to 4HI, A4WD or 2HI your vehicle
must be stopped or moving less than 2 mph (3.2 km/h)
with the transmission in NEUTRAL (N) and the engine
running. The preferred method for shifting out of 4LO
is to have your vehicle moving 1 or 2 mph (1.6 to
3.2 km/h). Turn the knob to 4HI, A4WD or 2HI. You
must wait for the 4HI, A4WD or 2HI indicator light to
stop flashing and remain illuminated before shifting
your transmission into gear.
If the 4HI, A4WD or 2HI knob is turned when your
vehicle is in gear and/or moving, the 4HI, A4WD or
2HI indicator light will flash for 30 seconds but will
not complete the shift unless your vehicle is moving
less than 2 mph (3.2 km/h) with the transmission
in NEUTRAL (N).

2-30
Shifting to NEUTRAL
To shift the transfer case to NEUTRAL first make sure
the vehicle is parked so that it will not roll:
1. Set the parking brake.
2. Start the vehicle.
3. Connect the vehicle to the towing vehicle.
4. Put the transmission in NEUTRAL (N).
5. Shift the transfer case to 2HI.
6. Turn the transfer case knob all of the way past 4LO
and hold it there for a minimum of 10 seconds. The
NEUTRAL (N) indicator light will come on.
7. Shift the transmission to REVERSE (R) for one
second, then shift the transmission to DRIVE (D)
for one second.
8. Turn the ignition to LOCK.
9. Place the transmission shift lever to PARK (P).
10. Release the parking brake prior to towing.Shifting Out of NEUTRAL
To shift the transfer case out of NEUTRAL:
1. Set the parking brake and apply the regular
brake pedal.
2. Start the vehicle with the transmission in PARK (P).
3. Turn the transfer case knob to the desired shift
position (2HI, 4HI or A4WD).
4. Put the transmission in NEUTRAL (N).
5. After the transfer case has shifted out of NEUTRAL,
the red light will go out. Shift the transmission lever
to the desired position.
6. A re
-engagement sound is normal when shifting out
of NEUTRAL.

2-89
Service Four-Wheel-Drive Warning Light
(If Equipped)
United States Canada
This light should come on briefly when you turn on the
ignition, as a check to show you it is working.
The SERVICE 4WD light comes on to indicate that
there may be a problem with the drive system and
service is required. Malfunctions can be indicated by the
system before any problem is apparent, which may
prevent serious damage to the vehicle. This system is
also designed to assist your service technician in
correctly diagnosing a malfunction.
Check Gages Light
United States Canada
The CHECK GAGES light will come on briefly when
you are starting the engine.
If the light comes on and stays on while you are driving,
check your coolant temperature and engine oil pressure
gages to see if they are in the warning zones.

4-52
Three important considerations have to do with weight:

the weight of the trailer,

the weight of the trailer tongue

and the weight on your vehicle's tires.
Weight of the Trailer
How heavy can a trailer safely be?
It depends on how you plan to use your rig.
For example, speed, altitude, road grades, outside
temperature and how much your vehicle is used to pull
a trailer are all important. And, it can also depend on
any special equipment that you have on your vehicle.Look in the following chart to find the maximum trailer
weight for your vehicle.
Axle
RatioMax.
Trailer Wt.GCWR *
2WD 3.42 5,300 lbs.
(2 406 kg)10,000 lbs.
(4 535 kg)
3.73 5,800 lbs.
(2 633 kg)10,500 lbs.
(4 762 kg)
4.10 6,300 lbs.
(2 860 kg)11,000 lbs.
(4 989 kg)
4WD 3.42 5,100 lbs.
(2 315 kg)10,000 lbs.
(4 535 kg)
3.73 5,600 lbs.
(2 542 kg)10,500 lbs.
(4 762 kg)
4.10 6,100 lbs.
(2 769 kg)11,000 lbs.
(4 989 kg)
* The Gross Combination Weight Rating (GCWR) is the
total allowable weight of the completely loaded vehicle
and trailer including any passengers, cargo, equipment
and conversion. The GCWR for your vehicle should not
be exceeded.