Chevrolet 2006 Silverado 1500 Pickup Owner's Manual page 322

If you think you will need some more ground clearance
at the front of your vehicle, you can remove the front
bumper lower air dam.
4-18
The front bumper lower air dam is held in place by a
series of push-pins located around the lower edge of the
front bumper. The push-pins are accessible from
underneath the front bumper. The following steps must
be performed on each of the push-pins to remove
the air dam:
1. Insert a tool into the
push-pin slot and pull
downward until the
push-pin snaps loose.