Any time I gear brake, I get this horrible sounding rattle/grinding that sounds almost as if it's coming from the exhaust. I can feel it in my cab and it doesn't happen all the time. I believe it occurs the most when the engine is warmed up. It sounds very much like when I had an exhaust braket loose and the exhaust pipe was bangin agains the frame. But my searches only found the exhaust was firmly attached, just as I left it. Any thoughts???