GMC C series 2002 Owner's Manual page 179

Before you do anything, turn on the hazard warning
flashers (if they have not been damaged).
When you call, tell the towing service:
D
That your vehicle has rear
D
The make, model and year of your vehicle.
D
Whether you can still move the shift lever.
D
If there was an accident, what was damaged.
When the towing service arrives, let the tow operator
know that this manual contains towing instructions.
The operator may want to see them.
Here are specific towing instructions:
5-12
-
wheel drive.
Towing Your Vehicle From the Front
(Front Wheels Off the Ground)
Before Towing
Block the rear wheels of the disabled vehicle. On vehicles
with air brakes, release the emergency brake system by
compressing the brake chamber springs as outlined in
this section. (This is to prevent the possibility of the
emergency brake being applied during towing.)
On vehicles with hydraulic brakes without an
electric/hydraulic parking brake, release the parking brake
fully by moving the lever to the fully
On vehicles equipped with an electric/hydraulic parking
brake option, remove the propshaft.
-
released position.