Severe vibration issue. started at about 65 mph and let off about 74. at it's peak, about same as holding a jack hammer instead of a steering wheel.. dealers are blaming tires, one idiot told me vibration was normal. it is not. the sound seems to be coming from passenger rear quarter area. three dealers cannot diagnose. it was a failing u-joint on the rear of the main driveshaft. mine failed i lost the yoke assembly and the driveshaft, and if going quicker - would have likely punctured the gas tank. likely resulting in a fireball.