GMC Sierra 2000 Owner's Manual page 85

CAUTION:
It is 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.
Don't leave your vehicle when the engine is
running unless you have to. 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, always set your parking brake and
move the shift lever to PARK (P).
-
If you have four wheel drive, your vehicle will
--
be free to roll even if your shift lever is in
--
PARK (P) if your transfer case is in
NEUTRAL (N). So, be sure the transfer case is in
-
a drive gear, two wheel high (2H) or four
-
high (4H) or four wheel low (4L)
NEUTRAL (N). See "Shifting Into PARK (P)" in
the Index. If you're pulling a trailer, see "Towing
a Trailer" in the Index.
REVERSE (R): Use this gear to back up.
To rock your vehicle back and forth to get out of snow,
ice or sand without damaging your transmission, see
"Stuck: In Sand, Mud, Ice or Snow" in the Index.
NEUTRAL (N): In this position, your engine
doesn't connect with the wheels. To restart when you're
already moving, use NEUTRAL (N) only. Also, use
NEUTRAL (N) when your vehicle is being towed.
-
wheel
--
not in
NOTICE:
Shifting to REVERSE (R) while your vehicle is
moving forward could damage your
transmission. Shift to REVERSE (R) only after
your vehicle is stopped.
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