I have just bought a 62 reg 450 for my wife. I immediately noticed the problem. I hear a knocking, clunking sound, I think from the front when I go over small bumps/potholes. I don't notice it over speed bumps. I have booked it in with Lexus Croydon for diagnosis. My previous car, a 4WD Volvo and my current car, Jaguar XJ do not have the problem on the same roads. I will report when I get the car back