Hi

I have asked this question to a few posters (?) in the C class group but thought I would ask it here as well.

I bought a used 03 C230 Kompressor Coupe with automatic trans. Love the car with the exception of what seems to be an air temp / road temp / tire temp / speed related roar coming from the back end.

When it happens, it sounds like a bad u-joint on past rear wheel drive cars I have driven. It starts around 45mph and quiets down as I go up in speed. Returns around 62 and is barely audible at 70+.

I recently had the tires road-force balanced and the problem appears to have gone away, but the morning temps have been in the high 60's. As soon as the air temp gets to around 72+, it comes back and is louder as the air temp goes up. But once the tires are warmed up after 10 or 15 miles at 55+ the volume of the roar diminishes regardless of speed but never really goes away.

The road-force balance seems to have helped quite a bit, but the issue still hangs around. My dealership has been great - they found noise in the differential a few months ago and replaced it under warranty. But since that repair they point back to tires which are only 7k miles old - Michelin Pilot Exalto's which I really like.

Any ideas on how to get rid of this noise?

Thanks -

Bassmith