GMC Sierra Instruction Manual page 427

426 Vehicle Care
Front Position All Other Models
If the flat tire is on the front of
the vehicle (all other models),
position the jack under the
vehicle, as shown.
Rear Position 1500 Models
5. If the flat tire is on the rear, for
1500 models position the jack
under the rear axle about 5 cm
(2 in) inboard of the shock
absorber bracket.
I n f o r ma t i o n P r o v i d e d b y :
Rear Position All Other Models
For all other models, position
the jack under the rear axle
between the spring anchor and
the shock absorber bracket.
If a snow plow has been added
to the front of the vehicle, lower
the snow plow fully before
raising the vehicle.
Make sure that the jack head is
positioned so that the rear axle
is resting securely between the
grooves that are on the
jack head.