GMC 1997 Safari Owner's Manual page 226

I
A vehicle can fall from a car carrier if it isn't
adequately secured. This can cause a collision,
serious personal injury and vehicle damage. The
vehicle should be tightly secured with chains or
steel cables before it is transported.
Don't use substitutes (ropes, leather straps,
canvas webbing, etc.) that can be cut by sharp
edges underneath the towed vehicle.
When your vehicle is being towed, have the ignition key
in the O W position. The steering wheel should be
clamped in a straight-ahead position, with a clamping
device designed for towing service. Do not use the
vehicle's steering column lock for this. The transmission
should be in NEUTRAL (N) and the parking
brake released.
If your vehicle has the all-wheel-drive option, it can
only be towed with all four wheels off the ground. A
dolly must be used under the un-raised wheels when
towing or the vehicle must be transported on a flat
bed carrier.
Don't have your vehicle towed with the wheels in
contact with the ground if it has all-wheel drive. If a
vehicle with all-wheel drive must be towed with
sling-type
or
wheel-lift equipment, then either the front
or rear wheels must be supported on a dolly.
NOTICE:
If your vehicle has all-wheel drive, do not have it
towed with the wheels in contact with the ground
or vehicle damage may occur. A dolly must be
used under the un-raised wheels when towing or
the vehicle must be transported on a flat
bed carrier.
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