GMC 1993 Suburban Owner's Manual page 231

6. Release the regular brakes.
It can be dangerous to get out of your vehicle if the shift lever is not
fully in
P
(Park) 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,
when you're on fairly level ground, use the steps that follow.
If you have four-wheel drive and your transfer case is in
N
(Neutral),
your vehicle will be free to roll, even i f your shift lever is in P (Park).
So, be sure the transfer case is in a drive gear-not in N (Neutral).
If you are parking on a hill, or i f you're pulling a trailer, also see
I
"Parking On Hills" in the Index.
When
kw
Are Ready to Leave After Parking on
B
HW
1.
Apply your regular brakes and hold the pedal down while you:
Q
Start your engine.
Shift into a gear; and
Q
Release the parking brake.
2. l e t up on the brake pedal.
3. Drive slowly until the trailer is clear of the chocks.
4. Stop and have someone pick
up and stow the chocks.
Maintenance When Traikr Towing
Your vehicle will need service more often when you're pulling a trailer. See
the Maintenance Schedule for more on this. Things that are especially
important in trailer operation are automatic transmission fluid (don't overfill),
engine oil, axle lubricant, belts, cooling system, and brake adjustment. Each
of these is covered in this manual, and the Index will help you find them
quickly. If you're trailering, it's a good idea to review these sections before
you start your trip.
Check periodically to see that all hitch nuts and bolts are tight.
4-63