Chevrolet 1999 Silverado 1500 Pickup Owner's Manual page 286

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Rear Position
Front Position All Other Models
3. Make sure the jack head is positioned so that the rear
axle is resting securely between the grooves that are
on the jack head. 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.
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