GMC 1999 Envoy Owner's Manual page 217

CAUTION:
It can be 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.
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, use the steps
that follow.
Always put the shift lever fully in PARK (P) with
the parking brake firmly set.
If the transfer case on four
in NEUTRAL, your vehicle will be free to roll,
even if your shift lever is in PARK (P). So, be
sure the transfer case is in a drive gear
-
NEUTRAL. See "Four Wheel Drive (Automatic
Transfer Case)" in the Index.
-
wheel drive vehicles is
--
not in
When You Are Ready to Leave After
Parking on a Hill
1. Apply your regular brakes and hold the pedal down
while you:
D
Start your engine;
D
Shift into a gear; and
D
Release the parking brake.
2. Let up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick up and store the chocks.
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