GMC Yukon Denalid Owner's Manual page 147

REVERSE (R): Use this gear to back up.
Notice: Shifting to REVERSE (R) while your
vehicle is moving forward could damage
the transmission. The repairs would not
be covered by your warranty. Shift to
REVERSE (R) only after your vehicle is
stopped.
To rock your vehicle back and forth to get out
of snow, ice, or sand without damaging your
transmission, see If Your Vehicle is Stuck in Sand,
Mud, Ice, or Snow on page 390.
NEUTRAL (N): In this position, your engine does
not connect with the wheels. To restart when
you are already moving, use NEUTRAL (N) only.
Also, use NEUTRAL (N) when your vehicle is
being towed.
CAUTION:
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Shifting into a drive gear while your
engine is running at high speed is
dangerous. Unless your foot is firmly on
the brake pedal, your vehicle could move
very rapidly. You could lose control and
hit people or objects. Do not shift into a
drive gear while your engine is running at
high speed.
Notice: Shifting out of PARK (P) or
NEUTRAL (N) with the engine running at high
speed may damage the transmission. The
repairs would not be covered by your warranty.
Be sure the engine is not running at high
speed when shifting your vehicle.
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