1999 GMC ENVOY Owners Manual

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2-21
Tow/Haul Selector Switch
Your vehicle is equipped
with a tow/haul selector
switch. This switch is
located on the shift knob.
You can use this feature to more efficiently tow or haul a
heavy load. See ªTow/Haul Modeº in the Index for
more information.
Four-Wheel Drive
Because your vehicle has four-wheel drive, you can
send your engine's driving power to all four wheels for
extra traction. To get the most satisfaction out of
four
-wheel drive, you must be familiar with its
operation. Read the part that follows before using
four
-wheel drive. You should use two-wheel drive (2HI)
for most normal driving conditions.
NOTICE:
Driving in the 4HI or 4LO positions for a long
time on dry or wet pavement could shorten the
life of your vehicle's drivetrain.
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2-22 Automatic Transfer Case
The transfer case switches
are to the right of the
steering wheel on the
instrument panel. Use these
switches 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. This setting also provides the best
fuel economy.
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2-23
AUTO 4WD: This setting is ideal for use when road
conditions are variable. When driving your vehicle in
AUTO 4WD, 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.
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.
NEUTRAL: Shift the vehicle's transfer case to
NEUTRAL only when towing your vehicle. See
ªRecreational Vehicle Towingº or ªTowing Your
Vehicleº in the Index for more information.
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.
Indicator lights in the switches show which setting you
are 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 stays on, you should take
your vehicle to your dealer for service. See ªService
4WDº in the Index for further information.
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Shifting to 4HI or AUTO 4WD
Press and release the 4HI or AUTO 4WD switch. 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
Press and release the 2HI switch. 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 3
mph (4.8 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).
Press and release the 4LO switch. You must wait for the
4LO indicator light to stop flashing and remain
illuminated before shifting your transmission into gear.
If the 4LO switch is pressed 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 3 mph (4.8 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, AUTO 4WD or 2HI your
vehicle must be stopped or moving less than 3 mph
(4.8 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). Press and release the 4HI, AUTO
4WD or 2HI switch. You must wait for the 4HI, AUTO
4WD or 2HI indicator light to stop flashing and remain
illuminated before shifting your transmission into gear.
If the 4HI, AUTO 4WD or 2HI switch is pressed when
your vehicle is in gear and/or moving, the 4HI, AUTO
4WD or 2HI indicator light will flash for 30 seconds but
will not complete the shift unless your vehicle is moving
less than 3 mph (4.8 km/h) with the transmission in
NEUTRAL (N).
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.
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4. Put the transmission in NEUTRAL (N).
5. Shift the transfer case to 2HI.
6. Simultaneously press and hold the 2HI and 4LO
buttons for 10 seconds. The red NEUTRAL light
will come on when the transfer case shift to
NEUTRAL is complete.
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 OFF.
9. Place the transmission shift lever to PARK (P).
10. Release the parking brake prior to towing.
Shifting Out of NEUTRAL
To shift 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. Press the button for the desired transfer case shift
position (2HI, 4HI, AUTO 4WD or 4LO).
4. Put the transmission in NEUTRAL (N).
5. Shift the transmission lever to the desired position.
After the transfer case has shifted out of NEUTRAL,
the red light will go out.
6. A re
-engagement sound is normal when shifting out
of NEUTRAL.
Parking Brake
To set the parking brake, hold the regular brake pedal
down with your right foot. Push down the parking brake
pedal with your left foot. If the ignition is on, the brake
system warning light will come on.
To release the parking brake, hold the regular brake
pedal down.
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2-26
Pull the BRAKE RELEASE lever fully. It is located on
the bottom of the driver's side of the instrument panel.
NOTICE:
Driving with the parking brake on can cause
your rear brakes to overheat. You may have to
replace them, and you could also damage other
parts of your vehicle.
If you are towing a trailer and you must park on a hill,
see ªTowing a Trailerº in the Index. That section shows
what to do first to keep the trailer from moving.
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. 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.
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2-27
2. Move the shift lever into PARK (P) position
like this:

Hold in the button 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).
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. 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).
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2-28 Torque Lock
If you are parking on a hill and you don't shift your
transmission into PARK (P) properly, the weight of the
vehicle may put too much force on the parking pawl in
the transmission. You may find it difficult to pull the
shift lever out of PARK (P). This is called ªtorque lock.º
To prevent torque lock, set the parking brake and then
shift into PARK (P) properly before you leave the
driver's seat. To find out how, see ªShifting Into
PARK (P)º in the Index.
When you are ready to drive, move the shift lever out of
PARK (P) before you release the parking brake.
If torque lock does occur, you may need to have another
vehicle push yours a little uphill to take some of the
pressure from the parking pawl in the transmission, so
you can pull the shift lever out of PARK (P).
Shifting Out of PARK (P)
CAUTION:
Before shifting out of PARK (P) you must fully
apply your regular brakes. Your vehicle can roll.
If you have left the engine running, the vehicle
can move suddenly. You or others could be
injured. If you're pulling a trailer, see ªTowing a
Trailerº in the Index.
Your vehicle has a Brake-Transmission Shift Interlock
(BTSI). You have to fully apply your regular brake
before you can shift from PARK (P) when the ignition is
in RUN. See ªAutomatic Transmission Operationº in
the Index.
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