GMC 2010 T-Series Owner's Manual page 143

Here are specific towing instructions:
Towing Your Vehicle From the Front
(All Wheels On the Ground)
The vehicle may be towed on all wheels provided the
steering is working. Remember that the power brakes
and power steering will not have power assist. Vehicles
with air brakes will not have brakes. There must be a
tow bar installed between the towing vehicle and the
disabled vehicle.
Before Towing
Block the 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, release the parking
brake fully by moving the lever to the fully-released
position.
If there is damage or suspected damage to the axle(s),
remove the axle shafts. Cover the hub openings to
prevent the loss of lubricant or entry of dirt or foreign
objects.
After Towing
1. Block the rear wheels and install axle shafts and/or
propshafts.
2. Check for proper phasing of universal joints.
3. Apply the parking brake system before
disconnecting from the towing vehicle.
4. Check and fill rear axle with oil as required.
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, release the parking
brake fully by moving the lever to the fully-released
position.
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