GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 137

CAUTION:
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Shifting the transfer case to 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 in Neutral. See Parking Brake on
page 2-50.
A parking brake symbol
is located next to the
N (Neutral) symbol as
a reminder to set the
parking brake before
shifting the transfer case
into N (Neutral).
N (Neutral): Shift to this setting only when the vehicle
needs to be towed. See Recreational Vehicle Towing
on page 4-47 or Towing Your Vehicle on page 4-47.
m
2 (Two-Wheel-Drive High): This setting is used for
driving in most street and highway situations. The front
axle is not engaged in two-wheel drive. This setting also
provides the best fuel economy.
m
4 (Four-Wheel-Drive High): Use this setting when you
need extra traction, such as on snowy or icy roads or in
most off-road situations. This setting also engages the
front axle to help drive your vehicle. This is the best
setting to use when plowing snow.
You can shift from Two-Wheel-Drive High to
Four-Wheel-Drive High or Four-Wheel-Drive High to
Two-Wheel-Drive High while the vehicle is moving.
In extremely cold weather, it may be necessary to stop
or slow the vehicle to shift into Four-Wheel-Drive High.
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