FYI: Early built 2001 W203 differential noise
If you own an early built 2001 W203 and if you hearing noise from you car differential while traveling at 65mph, the dealer needs to be notified and replace it before the warranty runs out.
In my case, my 2001 C240 differential start making a howling noise at 10,000 miles. The noise will appear when I am going at 65mph. The differential does not make the howling noise at any speed below or beyond 65 mph.
It took me more than year or almost 30,000 miles later to convince the dealer that there was a problem with the differential before they were willing to replace it. It was not until I finally got fed up and sent a letter to MB Canada; and, finally, the dealer took my complaint serious enough that the tech went out with me to test drive and listen for the noise. The tech heard it and had the dealer to replace the differential. The problem was resolved.
Just for your FYI.