I have a 2002 Chevrolet Blazer LS and when I am moving in reverse it makes this clicking/squeak noise.

 

U joints?

I'm sure we could all throw random ideas out there. But we need more info. How fast are you moving. Where is the noise coming from (rear end, transmission, transfer case (if 4x4))

 

I had it fixed we took it to a local shop, it was the rear disc brakes. The people we bought it from hadn't changed them in forever I guess they figured they were drum brakes? The guy at the shop said they had 1/8th inch layer of rust on them.

 

Very good. Glad you got the problem solved.