Chevrolet 2005 Silverado 1500 Pickup Owner's Manual page 311

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.
2. While continuing to pull
downward on the
push-pin, squeeze and
turn the expandable
end of the push-pin
with a tool until it
releases from
the retainer.
When you are back on roads, though, be sure to
replace the air dam.
Notice: Operating your vehicle for extended
periods without the front bumper lower air dam
installed can cause improper air flow to the engine
and may allow things like fog lamps or tow hooks
on the front of your vehicle to be damaged. Always
be sure to replace the front bumper air dam when
you are finished off-road driving.
3. Pull the push-pins and
lower dam assembly
away from the retainers
until the lower dam
is free.
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