GMC 2007 Sierra - Manual (Page 159)

2 m (Two-Wheel Drive High): This setting is
used 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.
{ 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 Parking Brake on page 169.
N (NEUTRAL): Shift the vehicle’s transfer case to
N (NEUTRAL) only when towing your vehicle.
See Recreational Vehicle Towing on page 424 or
Towing Your Vehicle on page 423 for more
information.
4 m (Four-Wheel Drive High): Use this setting
when you need extra traction, such a on snowy
or icy roads or in most off-road situations.
This setting also engages your front axle to help
drive the vehicle. This is the best setting to
use when plowing snow.
4
n
(Four-Wheel Drive Low): This setting also
engages the front axle and delivers extra
torque. You may never need Four-Wheel Drive
Low. It sends maximum power to all four wheels.
You might choose Four-Wheel Drive Low if
you are driving off-road in deep sand, deep mud,
deep snow, and while climbing or descending
steep hills. When operating in Four-Wheel Drive
Low, the gear ratio provides additional torque
when compared to Four-Wheel Drive High. The
transmission gear shift feel will be exaggerated.
If the SERVICE 4WD message stays on the Driver
Information Center (DIC), you should take your
vehicle to your dealer for service. See DIC
Warnings and Messages on page 270 for further
information.
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