GMC 2012 Savana Owner's Manual page 338

Two-wheel-drive vehicles should
not be towed with all four wheels
on the ground. Two-wheel-drive
transmissions have no provisions
for internal lubrication while being
towed.
The vehicle was not designed to be
towed with all four wheels on the
ground. To properly tow these
vehicles, they should be placed on
a platform trailer with all four wheels
off the ground.
Use the following procedure to tow
the vehicle from the rear:
1. Attach the dolly to the tow
vehicle following the dolly
manufacturer's instructions.
2. Drive the rear wheels onto the
dolly.