I have a "new" 2005 LS430 (less than 1K mi) that has this thrumming vibration that comes mainly through the body and seat and is most noticeable in the 40 to 50 mph range. The dealer has balanced tires (Road Force Equipt), switched wheels and tires, installed new tires, and the problem remains. We attempted to assess it further by running in gear with the car on a hoist, but traction control prevented going above idling speed. The drive train is a logical suspect, but does anyone have a suggestion about how to best define this problem and/or solve it? Is this typical for LS's with the rubber couplings on the drive shaft ends? :(
