have an 05 Yukon XL Denali, new tires (balanced checked two different dealers) new u-joints, new tie rods (all four) plus 4 wheel alignment. Has vibration that gets worse the faster you go, very noticeable between 65 - 75 mph. don't know what else to check? rotors? engine (no engine light), ball joints? any help is appreciated. Thanks, Scottp