GMC 1996 Sierra Owner's Manual page 76

PARK (P): This locks your rear wheels. It's the best
position
t o
use when you start your engine because your
vehicle can't move easily.
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).
I
CAUTION: (Continued)
-
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-wheel
high (4H) or four-wheel low (4L)
--
not in
NEUTRAL (N). See "Shifting Into PARK (P)" in
the Index. If you're pulling a trailer, see "Towing
a
Trailer" in the Index.
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