I have an 03 Silverado 2500HD with the 6.0. It sits outside all the time. For the last few months, when I start it and put it into gear (mainly reverse to get out of the driveway), I am getting squeeks from the drivetrain. It sounds like it is coming from behind the drivers seat, so maybe from the driveshaft back. The squeeks are very high pitched. As soon as I put the truck into drive, the squeeks disappear after a few seconds, and everything is fine. I took it into the dealer, and they couldn't replicate the issue (Because the truck had warmed up), but said it was most likely caused by humidity, and the rotors being slightly damp. I don't buy this though, because the squeek occurs when I am not using the brakes. Anyone heard of this issue before? It's not a big deal, but it is kinda annoying.