My truck is a 2003 Silverado Z71 4x4, and has 70k miles on it. Alway's garage kept, etc. I have developed a problem with a really fast/loud rattling sound, and it only when traveling over really rough pavement or driveway. I think it has to be suspension related, but can't determine what it would be. The first time I heard it, I thought it was some type of gear stripping/grinding, but I now think it is rattling and has something to do with the suspension system. I know I am not being real clear on what it sounds like, but it is hard to describe. Like I said, it is a fast rattling sound, almost to the point it could sound like gears slipping/striping. Upon looking, the only thing I can find wrong is on the drivers rear side, the bump stop is missing. I can't imagine that is causing the sound I am hearing, as that should only have an impact if hauling something really heavy or doing something to bottom out the suspension. I am replacing it, but the other issue seems to be more critical right now. The only time I hear it is on really rough road or on a driveway with large rock that causes a lot of suspension jumping. Any ideas what this could be?