hey, my truck has started to make a clunk when i let off the throttle. i dont even have to push it that hard to make it do it. checked u joints and it has a dana 80 rear end so i dont think it would be that but who knows. if i go between reverse and drive it will do it too. any one know what it could be? 6.0 cc lb dually auto 4x4 239 000 miles