Not long ago, I posted a thread on a power train vibration problem I was having with my 2007 GMC Sierra Classic, 2500HD. While the vibration is always present, it noticeable (and quite loud) when I am towing my 5th wheel between 55-65 MPH. The GVWR for the truck and 5th wheel is 17,950, which is well below the rating for the truck. The dealership has been messing with the truck for over a year and a half trying to figure out the problem, and the cure. My patience grew thin, so I wrote a letter to the President & CEO of General Motors. Would you believe I actually received a response?? Today I received a phone call from the executive office of GM. They basically told me the vibration is a characteristic of the truck--live with it!! With that sort of customer service, and attitude, it is no wonder GM is going down the tubes. My truck is a 2500HD, 4WD, SRW, with a crew cab, and long bed. Take my advice, and do not buy one of these trucks..........