Chevrolet 2008 Express Owner's Manual page 340

To release the spare tire from the secondary latch:
CAUTION:
{
Someone standing too close during the
procedure could be injured by the jack. If the
spare tire does not slide off the jack
completely, make sure no one is behind you or
on either side of you as you pull the jack out
from the under spare.
1. Check under the vehicle to see if the cable end is
visible.
5-94
If the cable is not visible,
start this procedure at
Step 6.
2. Turn the wrench counterclockwise until
approximately 6 inches (15 cm) of cable is exposed.
3. Connect the jack handle (A) and jack handle
extension (B) together and press the retention
clip (arrow) so it engages.