Lexus LS 2007+ :: Loud Thump In Rear At 10-45 Mph - 2009 LS460 AWD

I just picked up a used 2009 LS 460 AWD last week with 45K miles. I have put about 1000 miles on it so far myself.

When I hit any small depression in the road at 10-45 mph I hear a thump in the rear. The bigger the depression and the more weight in the backseat, the louder the thump noise and even an occasional bottoming out feeling occurs. It hasn't happened at highway speeds so far.

The bottoming out feel occurs only with a medium to large depression. I am not talking about a pot hole, just pavement depressions where two sections are not of equal height or you are transitioning from a primary road to a side street and the is a depression to allow for water run off, etc.

If I have someone sitting in the passenger seat and the backseat and accelerate quickly from a dead stop, I get a similar rear thump and even a bottoming out feel. This occasionally occurs even without a without a depression in the road. With no one in the back seat it does not do it unless there is a big depression in the road.

Finally, when cornering on a 270 degree off ramp at 40 to 50 MPH the rear end will start to hop and bounce. If I slow down to 15-20 mph it goes away. Still, it is irritating and embarrassing. I have tried all comfort settings and get the same results.