Alright so this is a question about my dads truck. The title says what kind of truck it is and it has 317,000 miles on it ( gotta love chevys ). Recently there has been an odd noise that comes and goes. The noise sounds like metal spinning against metal. The sound seems to be coming from under the middle of the cab. I was thinking U joints because they are still the factory joints. Usually when u joints go there tends to be vibration and its not vibrating. I know this is a very general question, but I am somewhat stumped on this one.