GMC 2003 Yukon Owner's Manual page 117

{
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.
Do not 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 will not move, even when
you are on fairly level ground, always set your
parking brake and move the shift lever to
PARK (P). See "Shifting Into Park (P)" in the
Index. If you are pulling a trailer, see "Towing
a Trailer" in the Index.
{
CAUTION:
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. 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. See "Shifting into Park (P)" in the
index.
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 You Are Stuck: In Sand, Mud, Ice or Snow on
page 4-52 .
2-23