2010 GMC Sierra 1500 Crew Cab Owner's Manual - Page 569

{ WARNING: Getting under a vehicle when it is jacked up is dangerous. If the vehicle slips off the jack, you could be badly injured or killed. Never get under a vehicle when it is supported only by a jack. { WARNING: Rear Position - 1500 Models Rear Position - All Other Models 5. If the flat tire is on the rear, for 1500 models position the jack under the rear axle about 2 inches (5 cm) inboard of the shock absorber bracket; for all other models, position the jack under the rear axle between the spring anchor and the shock absorber bracket. If you have added a snow plow to the front of your 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. 6-109 Raising your vehicle with the jack improperly positioned can damage the vehicle and even make the vehicle fall. To help avoid personal injury and vehicle damage, be sure to fit the jack lift head into the proper location before raising the vehicle. 6. Turn the wheel wrench clockwise to raise the vehicle. Raise the vehicle far enough off the ground so there is enough room for the spare tire to fit under the wheel well.