I just bought a 1982 300TD, the car runs great except for a few squeaks and thuds here and there. Basically I have no problems with the car when I am just driving around town. However, I have taken the car on the interstate between Chattanooga and Nashville (120 miles) 3 times so far and everytime without fail I get a loud thumping/banging noise that sounds like it is coming from the read end. The noise is so loud it sounds like someone is under the car banging with a hammer. The noise continues as I slow down but goes away when I stop. I have noticed it doesn't start until I have driven at least 60 miles. Also, when I hear the noise the car is still riding smoothly and there is no loss of power. Any help is greatly appreciated, thanks.