I purchased a 2006 C230. After a couple of weeks I started hearing a grinding/clicking noise coming from the back. It tends to increase when I speed up, and louder when ever I hit a hole/uneven pavement... i took it to a shop today and they couldn't figure it out.. If anyone has this happen to them please let me know..

 

A good place to start is for you to jack up the rear of the car and spin the wheels by hand & see if you can hear it. If you can, it will be much easier to isolate the source.

When I changed the wheels on my C320, it started a clicking sound in the back which wasn't there before. It drove the tire techs crazy for about an hour. It turned out that a couple of the lug bolts were just a hair longer than the rest of them, and with the different wheels, they managed to rub against something behind the wheel hub. thankfully it didn't hurt anything but that clicking sounded scary & caused sufficient anxiety for all of us during that hour or so.

 

Thank you for replying... When I took it to the shop they put it on a lift and started spinning the wheels, then they took the wheels off and still couldn't figure figure it out... I don't think it's the lug nuts, because whenever I go over a whole it feels like something is loose..

 

If the noise increases as you speed up, it has to be related either to your wheels or your differential. Getting louder on pot holes only adds another piece to the puzzle. Without being there to hear it, I don't think I can offer any more useful advice.