So my service director is stating that they have hooked the vibration testing machine up to my truck. They stated that there are no spikes in the graph and that they do not see anything that gm would advise them to do work on. I am going to be taking a ride with the technician on Monday. I asked them to balance the rear drive shaft, they didn't do it. I told them about shimming the engine 3mm, I told them about the rear leaf springs and nothing. Getting frustrated!