Hi all. My wife's 2013 C350 Sport with 95k on the clock has a quite pronounced noise (a low-level growling is the only way I can describe it) that starts to be quite noticeable after 70MPH. There is zero vibration in the steering wheel or in the seat of your pants, so I have ruled out an out-of-balance tire, alignment issue, wheel bearing, warped rotor, etc. The car has new tires and a fresh balance and alignment, and new brakes, and none of these cured the issue, so it is obviously driveline related. My guess is tranny or driveshaft center-bearing mount (don't remember the name of that exactly) that at speed causes an imbalance, or maybe an out-of-balance driveshaft or one of the two half-shafts (rear axle shafts). It doubt it's the latter though. I have heard that the tranny mounts and the center mount of the driveshaft are known to go bad, causing an imbalance in the entire assembly at speed, thus creating the growling effect. Any input would be greatly appreciated. Cheers.

 

I would definitely inspect the engine and transmission mounts first. The transmission mount is relatively easy to access and remove for visual inspection. At 95k miles, I wouldn't be surprised if it needed replacement. My CLK used to have a growl when cold and when going fast on the highway and replacing all 3 mounts fixed the problem. I couldn't believe how much smoother it got. This was at the 120,000 km mark.

 

I agree xsever. I will replace the very inexpensive trans mount first. if that's not it, then i'll check engine mounts and driveshaft center support bearing. The latter is def a possible culprit. Tnx mate.

 

It's very easy to check if the engine mounts need replacement. Do a search on youtube and you'll see. Basically you need a person to watch the engine while you're inside, in Drive, with all the brakes applied and revving. If the engine jumps up or jumps and tilts to one side, then one or both engine mounts are shot. Watch the video. They will help and good luck.

 

tnx mate. will do.

 

How about the flex couplings on either end of the driveshaft, those wear out too ...