deafjeffjr

Hey all, my 2011 c300 4MATIC is at 205k and I believe it could be finally experiencing a front differential going bad. Quick recap of work up to this point, I've personally replaced the entire rear sub frame, struts, diff fluid change etc. Now to the front, roughly 5k miles ago, I had to replace a failed right CV axle, so I went ahead and replaced driver side as well. In addition, both front struts and front diff fluid change. I'd say since the CV axle change, I've had a rotational noise, whining/grinding/howling. The noise is constant based on my speed. Its predominant around 25-40mph and its there turning left, right, or straight. No sight of diff fluid leaks. I'll attach two videos for input, one of me driving to hear the rotational noise and another under the vehicle showing a noticeable "clicking" noise at the front shaft to diff. Do I have a failed pinion bearing in the diff? Team, please share your thoughts.

https://youtu.be/iY1taYbkefA?si=lcLJ7ZbJRy_qq0y_

https://youtu.be/-SuzHrJVu2A?si=Fi5XsQxJ2hca8SKP

TimC300

Im not an expert. But if it were me I would drain the front diff and inspect the oil for any metal. Refill with proper amount of Mercedes spec gear oil. I used the Febi 75W-85 GL5 in mine. My operators manual says the front diff holds 1.1 quarts, but only something like .7 came out so that's what I put back in and seems to be running good.

I watched the video and can hear what you describe. I just cant tell where its coming from with headphones on.

have you inspected the intermediate shaft bearing on the drivers side? I recently read someone in a few posts below about a failed bearing and they can clearly look in and see it. That's why I just thought about it.

Sorry cant be more help. But i wouldn't drive around with it like that until fixed.