Dude - been posting on this topic lately and as i stated in other thread, i think it may be my sliding covers as well. Today ( in the rain )
i used some old cups to hold the covers in place so they wouldnt slide and the clunks/thuds almost disappeared. I think IT only happened once but that may have been a NORMAL noise coming from the back of the truck. I hope this sovled my problem. will post tomorrow on progress. thanks to all for their input... jer