Coming from sounds like left rear of truck, sounds like someone is hitting the cladding with the handle part of a screwdriver, only happens when I'm on the highway. Any clues? Geez, I just love sinking money into this truck, it never seems to end, windows 3 times , cd player 3 times, 02 sensors, hmmmm, theres more let me think,,,lol... anyway any suggestions? It's not the rear door handle, its not the jack or anything loose in the back, probably underneath. Could it be the driveshaft?,,, thanks again,,,