2002 GMC ENVOY transfer case

2-23
Automatic Transmission Operation
There are several different positions for your shift lever.
PARK (P): This position locks the rear wheels. It's the
best position to use when you start the engine because
your vehicle can't move easily.
CAUTION:
It is 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.
Don't leave your vehicle when the engine is
running unless you have to. 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, always set your parking brake and
move the shift lever to PARK (P).
CAUTION: (Continued)
CAUTION: (Continued)
If you have four-wheel drive, your vehicle will be
free to roll
-- even if your shift lever is in
PARK (P)
-- if your transfer case is in
NEUTRAL. 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.
See ªShifting Into PARK (P)º in the Index. If
you're pulling a trailer, see ªTowing a Trailerº in
the Index.
Ensure the shift lever is fully in PARK (P) before
starting the engine. Your vehicle has an automatic
transmission shift lock control system. You have to fully
apply the regular brakes before you can shift from
PARK (P) when the ignition key is in RUN. If you
cannot shift out of PARK (P), ease pressure on the shift
lever
-- press the button on the shift lever and push the
shift lever all the way into PARK (P) as you maintain
brake application. Then move the shift lever into the
gear you wish. See ªShifting Out of PARK (P)º in
the Index.

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.

2-32
Shifting Into PARK (P)
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. With four
-wheel drive, your
vehicle will be free to roll
-- even if your shift
lever is in PARK (P)
-- if your transfer case is
in NEUTRAL. 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.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set. If you're pulling a
trailer, see ªTowing a Trailerº in the Index.
1. Hold the brake pedal down with your right foot and
set the parking brake.
2. Move the shift lever into
PARK (P) like this:

Press the button in on
the front of the lever.

Push the lever all the
way toward the front
of the vehicle.
3. Turn the ignition key to LOCK.
4. Remove the key and take it with you. If you
can leave your vehicle with the key, your vehicle is
in PARK (P).

2-33
Leaving Your Vehicle With the
Engine Running
CAUTION:
It can be dangerous to leave your vehicle with the
engine running. Your vehicle could move
suddenly if the shift lever is not fully in PARK (P)
with the parking brake firmly set. If you have
four
-wheel drive, your vehicle will be free to
roll
-- even if your shift lever is in PARK (P) -- if
your transfer case is in NEUTRAL. 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. And, if you leave
the vehicle with the engine running, it could
overheat and even catch fire. You or others could
be injured. Don't leave your vehicle with the
engine running unless you have to.
If you have to leave your vehicle with the engine
running, be sure your vehicle is in PARK (P) and your
parking brake is firmly set before you leave it. After
you've moved the shift lever into PARK (P), hold the
regular brake pedal down. Then, see if you can move the
shift lever away from PARK (P) without pressing the
button on the shift lever. If you can, it means that the
shift lever wasn't fully locked into PARK (P).

2-36
Running Your Engine While
You're Parked
It's better not to park with the engine running. But if you
ever have to, here are some things to know.
CAUTION:
Idling the engine with the climate control
system off could allow dangerous exhaust into
your vehicle. See the earlier Caution under
ªEngine Exhaust.º
Also, idling in a closed-in place can let deadly
carbon monoxide (CO) into your vehicle even if
the fan is at the highest setting. One place
this can happen is a garage. Exhaust
-- with
CO
-- can come in easily. NEVER park in a
garage with the engine running.
Another closed-in place can be a blizzard.
See ªBlizzardº in the Index.
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.
Don't leave your vehicle when the engine is
running unless you have to. If you've 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, always set your parking brake and
move the shift lever to PARK (P).
If you have four-wheel drive, your vehicle will
be free to roll
-- even if your shift lever is in
PARK (P)
-- if your transfer case is in
NEUTRAL. 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.
Follow the proper steps to be sure your vehicle won't
move. See ªShifting Into PARK (P)º in the Index.
If you're pulling a trailer, see ªTowing a Trailerº in
the Index.