Chevrolet 2004 Express Van Owner's Manual page 330

Turn the ratchet counterclockwise to lower the spare tire
to the ground. If the spare tire does not lower to the
ground, the secondary latch is engaged causing the tire
not to lower. See "Secondary Latch System" later in
this section.
5-80
When the tire has been lowered, pull the tire toward you
so you can reach the tire retainer and pull it up
through the wheel opening.
If you have a vehicle which was completed from a cab
and chassis, refer to the information from the body
supplier/installer.
The spare tire is a full-size tire, like the other tires on
your vehicle.