The lock on the spare tire rack of my 2006 Chevy Silverado is screwed up - how do I remove it? Will the rack function without it? If not, what replacement parts are available?

ooops a daisy that is a tuffy, mine had a special tool get get to the part that allows it to drop
go to chev, dealer buyone n parts department.

there should be screws near the inner handle and check around the perimeter of the plastic panel

I have the same problem and it looks like a wire one, but i have no bar to twist the wire off to get the spare tire

get something and pry down on it while someone cranks on the cable

There is a place at the rear, into which you put the jack handle, then turn counter clockwise and a cable releases the tire.

Look in your glove box and see if you have the PRO code U89: wiring harness, car trailer
It's common to have the trailer harness already installed in your Silverado without you know and the dealer can pull it out for you from where it's tucked up in the frame passenger side by the spare tire for the simple cost or $65.00.
http://www.etrailer.com/tv-wiring-install-2006-chevy-silverado.aspx
Thank you for using fixya and good luck.

push the tire up with you knee and move the hang down rod over so the tire can drop.It can be a little hard.

it should be a long flathead screw driver inbetween rear bumper and tailgate

This is the worst GM engineering i have ever seen !!!! The secondary locking mech. rust itself in the locked position on will NOT allow the tire to lower. After lowering the tire down approx. 2-4" the saftey lock is still engaged. I was able to reach above the tire and remove the bolt holding the hoist in place. {15 mm wrench}. Keep a floor jack under the tire to support it and as not to fall on your head. After removing the bolt the hoist is hooked on the frame member and must be lifted off to remove. Once you get it on the garage floor it is possible to disengage the locking mech. with a few tools and a big hammer. Good luck This should be a Recall

Is the wheel the correct size? If so, then don't worry about it. It's just a spare. If it's completely wrong, then get the right one at a junkyard.