2002 Mercedes C320 vibration

We have an 2002 Mercedes C320 with about 20K miles. If has low freq vibration and I’m pretty sure it’s the tranny – and normal for this vehicle. But I’d love to get some more input from others.

The 2002 Mercedes C320, for maximizing fuel economy has transmission that shifts up into the tallest gear whenever possible (light throttle, medium speed) and the torque converter locks (again normal, designed to do this) to limit slipping and maximize effeciency.

At the lower rpm, there is vibration that I feel in the 45/50 mph all the way up to about 70 mph. Yep, when you lift throttle it is gone. I typically drive 75-80 on the freeway with ours so it doesn’t bug me alot on long trips, but the vibration of 2002 Mercedes C320 really bugs me otherwise.

Is that consistent with others experience. Those with the loaded models apparently have some active noise cancelation technology in the audio system of 2002 Mercedes C320 – maybe that is Honda’s way of dealing with it.

I plan to talk to the dealer of 2002 Mercedes C320 about it and see if they have had complaints there or if they have done anything different on the 2002 Mercedes C320 – seems like a simple chip reprogramming could make that lock up less agressive.

Possible causes:
1. If the noise is constant then might be bad wheel bearing(s).
2. If it occurs when accelerating around 55mph then it could be the transmission “lugging”. Lugging occurs when the transmission is in overdrive at a very low rpm. This is normal to an extent. If it lugs hard then the vibration is transmitted through the engine mounts of 2002 Mercedes C320.
3. Bad engine mounts? Does the engine shake when 2002 Mercedes C320 idling?

Anyway, some of the 2002 Mercedes C320 could have exhaust’s A pipe resonant problem at engine speed of 2100-2300 RPM. So that could be 30-40 MPH around town or 65-70 MPH on highway. It feels and sounds like transmission is in the wrong gear. But it is mere exhaust pipe resonating: no mechanical problem with engine or transmission of 2002 Mercedes C320.