GMC 1997 Safari Owner's Manual page 230

Towing From the Rear (All-Wheel Drive)
A towing dolly must be used under the front wheels
when towing from the rear:
NOTICE:
Do not tow with sling-type equipment or the rear
bumper system will be damaged. Use wheel-lift
or car-carrier equipment. Additional ramping
may be required for car-carrier equipment. Use
safety chains and wheel straps.
Towing a vehicle over rough surfaces could
damage a vehicle. Damage can occur from vehicle
to ground or vehicle to wheel-lift equipment. To
help avoid damage, install a towing dolly and
raise the vehicle until adequate clearance is
obtained between the ground and/or
wheel-lift equipment.
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