When I have a full tank of gas I have a thump coming from the rear end. After the gas tank is less than full the noise goes away. I have read other concerns by Lexus and Toyota owners going back to 2007 and they have reported the same problem. No one has received information from Toyota or Lexus to resolve this condition. I had my car at the local Lexus dealer to have this condition checked. They said they could not duplicate the problem. I heard the thump right after leaving the dealer, on just under a full tank of gas.