GMC 1996 Sierra Owner's Manual page 225

Front Towing
Tow Limits
--
35 mph (56 k d h ) , 50 miles (SO km)
If these limits must be exceeded, then the rear wheels
have to be supported on
n
dolly.
Rear Towing
NOTICE:
Towing pickup models from the rear while loaded
with heavy cargo may cause the frame side rails
to flex sufficiently to allow the pickup box to
contact the cab and could cause damage to the
cab and/or box.
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