GMC SIERRA 1994 Manual page 217

Towing From the Front
If you have a two-wheel drive vehicle, don't have your vehicle towed on
the rear wheels, unless you must. If the vehicle must be towed on the rear
wheels, don't go more than 35 mph (56 km/h) or farther than 50 miles
(80 km) or your transmission will be damaged. If these limits must be
exceeded, then the rear wheels have to be supported on a dolly.
If your vehicle has the four-wheel drive option and the transfer case is
engaged, a dolly must be used under the rear wheels when towing from the
front .
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