GMC 2011 Sierra Owner's Manual page 318

Turn the steering wheel left and
right to clear the area around the
front wheels. For four-wheel-drive
vehicles, shift into Four Wheel
High. For vehicles with StabiliTrak
turn the traction control part of the
system off. Shift back and forth
between R (Reverse) and a forward
gear, spinning the wheels as little as
possible. To prevent transmission
wear, wait until the wheels stop
spinning before shifting gears.
Release the accelerator pedal
while shifting, and press lightly
on the accelerator pedal when
the transmission is in gear. Slowly
spinning the wheels in the forward
and reverse directions causes a
rocking motion that could free the
vehicle. If that does not get the
vehicle out after a few tries, it might
need to be towed out. Recovery
hooks can be used, if the vehicle
has them. If the vehicle does need
to be towed out, see
®
,
These hooks, when used, are
under a lot of force. Always pull
the vehicle straight out. Never pull
on the hooks at a sideways angle.
The hooks could break off and
you or others could be injured
from the chain or cable
snapping back.
.
For vehicles with recovery hooks at
the front of the vehicle, you can use
them if you are stuck off-road and
need to be pulled to some place
where you can continue driving.