That is a common complaint on that engine, especially with an automatic. You have a low mileage car, but it might help to replace the motor mounts and you might get rid of some of the buzz. A 4000 rpm you are running at about 70% of redline which is a good place to be for efficiency. It is a pretty speedy engine and really does not pull well until over 3000 rpms. I have a 5 speed manual on a 300E, and at highway speeds I am looking for another gear also.

__________________
Junqueyardjim
Christianity, if false, is of no importance, and if true, of infinite importance. The only thing it cannot be is moderately important. C.S. Lewis



1983 Mercedes W123 240D 4 Speed 285,000 on the road with a 617 turbo, beautiful butter yellow, license plate # 83 240D INDIANA

2003 Jaguar Type X, AWD. beautiful, good mileage,
Mom's car, but I won't let her drive it!