ethanr24

Adi-Benz

Does it get louder when you go faster

ethanr24

Not at all, I only hear when I'm coasting down to around 40mph. Anything under 40 and it goes away

C300CA

The other way around: when you slowly speed up from below 40 mph to above, do you hear that? "Slowly" to minimize engine/exhaust running noise so it will not cover the whining noise.

ethanr24

I don't hear it at all when speeding up

C300CA

When whining occurs, if you shift to N, do you still hear it? I assume your 'coasting' was in D.

ethanr24

it stops when in N, must mean something with the transmission

JimmyKudo

It could be the rear differential resonating at a certain RPM as well. They're known to whine when no power is applied. If you press the gas and keep it at 40, as opposed to only when you're winding down, does it still make noise? If you have a long hill nearby (any incline should be good) try putting cruise control to 40mph and see if you still hear it when it's under load.

Funkwagen

Can you tell if the whine is coming from the front or rear of the car?

It's pretty common to have a minor whine at certain speeds with no load and I think it comes from the front diff or prop shaft. Not sure which, but I've had that noise come and go for over 150,000km with no issue.

Jayd3n

Im having the same issue with my car (2010 c300 4matic aswell). It began noticing it when I put new wheels on my car, so im not sure if its something to do with that or something else. Sounds like the whine is coming from the front passenger side

ethanr24

I went out and tested for a bit, can confirm the noise is still there when I shift into N. Hope that narrows it down.

ethanr24

Sounds like it’s coming from behind and below the center controls.

ethanr24

It’s not as loud but I still hear when cc on 40

W204Motorsports

I don't think its the transfer case because it would always whine(Hum/grind), regardless of speed and would continue to do so even if put in neutral. Does the whine happen when you let of the gas and start coasting at 40mph ?

If so, I had this issue once, a really faint whine only from 42-45mph when letting off the throttle. I did some research and all I found what a TSB on the clip holding the shifter linkage. I went under and saw the clip holding the shifter lever was crooked ( Must have reinstalled it poorly when changing transfer case bearings). I removed it and installed it correctly and the whine never came back.

xsever

Would you happen to have the TSB saved still to share it with us?

W204Motorsports

Unfortunately I can't seem to find it right now, here is the thread where we discussed the same issue;
https://mbworld.org/forums/c-class-w...eleration.html

ethanr24

I'm hearing the same noise your describing. I can also hear when in cc around that speed. Ill have my service tech look into it and post back with the results when I can