GMC 2011 Sierra Owner's Manual page 354

the Four-Wheel Drive High position
when extra traction is needed, such
as on snowy or icy roads or in most
off-road situations. This setting also
engages the front axle to help drive
the vehicle. This is the best setting
to use when plowing snow.
setting also engages the front axle
and delivers extra torque. You may
never need this setting. It sends
maximum power to all four wheels.
You might choose Four-Wheel
Drive Low while driving off-road in
deep sand, deep mud, deep snow,
and while climbing or descending
steep hills.
If the vehicle has StabiliTrak
shifting into Four-Wheel Drive
Low will turn Traction Control and
StabiliTrak off. See
.
Use
Shifting the transfer case to
N (Neutral) can cause the vehicle
to roll even if the transmission
is in P (Park). You or someone
else could be seriously injured.
Be sure to set the parking brake
before placing the transfer case
This
in N (Neutral). See
transfer case to N (Neutral)
only when towing the vehicle.
See
®
,
information.
If the SERVICE 4 WHEEL DRIVE
message stays on, you should
take the vehicle to your dealer for
service. See SERVICE 4 WHEEL
DRIVE message under
.
.
Shift the vehicle's
or
for more
Turn the knob to the Two-Wheel
Drive High position. This can be
done at any speed, except when
shifting from Four-Wheel Drive Low.
See Shifting Out of Four-Wheel
Drive Low for more information.
When Four-Wheel Drive Low is
engaged, vehicle speed should
be kept below 72 km/h (45 mph).
Extended high-speed operation in
Four-Wheel Drive Low may damage
or shorten the life of the drivetrain.
To shift to the Four-Wheel Drive
Low position, the ignition must be
in ON/RUN and the vehicle must be
stopped or moving less than 5 km/h
(3 mph) with the transmission in
N (Neutral). The preferred method
for shifting into Four-Wheel Drive
Low is to have the vehicle moving
1.6 to 3.2 km/h (1 to 2 mph).