It has been a great car thus far. It is my daily driver, ( 140 miles / day ). It seems to be a much more "solid" car than my 2005 E320 Wagon, that I have had since new. It is definitely coming from the rear of the car. The exhaust system is new, new hangers as well. I have had the tires rotated since the noise began, and, it did not make any difference. I am "blogging" the service of the W124 if anyone is interested.... The sound is defintely a "grumbling" rotational sound.