Hey guys, I'm still new to this page and the diesel world in general. When I'm drivin my 01 24v if I have it half throttle or so and ease into letting off my truck makes a drone sound (dull howling) but when I'm not on the throttle or ***** deep in it the situation doesn't happen. Only half throttle and it has to do with the throttle like I said when I'm off the throttle its completely normal. It's not my tires either. Lol. It doesnt effect anything it is annoying though. Any Ideas?

 

muffler missing?

 

Yeah but my buddys truck with straight pipe doesnt make the sound. Its not like an exhaust drone.