Strange whining sound (video in post)
The only thing that seems to affect the sound is the vehicle speed. It is not affected by:
- RPM
- Gear, or N or D
- Acceleration, deceleration or braking
- Turning left or right
- Empty or fully loaded car
- Going uphill or downhill
It's a little difficult to point out where it is coming from, but I would say from the middle or the front of the car. I had a bad differential before and that was another kind of sound.
Thanks a lot for any input.





The metal particles from the gear wear pits the ball bearings race... oil change plus a magnetic plug are the 1st line of defense.
Once serviced I would totally disregard that noise, given new diff oil ASAP...
No danger.
😎
Last edited by CaliBenzDriver; Nov 17, 2021 at 03:00 PM. Reason: intermed
The metal particles from the gear wear pits the ball bearings race... oil change plus a magnetic plug are the 1st line of defense.
Once serviced I would totally disregard that noise, given new diff oil ASAP...
No danger.
😎




do you see a fat pipe that runs from front to back? That's the propeller shaft.
In the middle of it.. that the intermediate shaft bearing.
Take a picture... I'll point it out or google it.
Trending Topics




Look down the line at Differential Input Shaft BEARING... when neglected these become musicians to demand attention.
.
.The Best of Mercedes & AMG
The dealer diagnosed it using a Chassis Ear, which is a system with small microphones that can be attached to chassis components and a speaker with a switch that allows the technician to listen to each one individually on a road test to pinpoint the issue. They attached microphones to the transmission output shaft, transfer case, rear differential, and center support...The noise was clearly coming from the center support bearing. It did take a couple of attempts due to the noise clearing up so quickly, we decided to install the microphones before the shop closed for the day and leave the car parked outside the dealership all night in -25c weather prior to road testing first thing in the morning. Another clue was a slight vibration that could be felt by placing your hand on the transmission tunnel right behind the center console, which is where the center support is attached.
Replacing the center bearing reduced the noise by 90%, but I still a whining noise in cold weather at 40km/h, but only at 40km/h +/-. It's fine at 35, fine at 45, only when the speedo is right at 40 does it whine. It also quiets down within a couple kilometers of driving, weather dependent. My theory is that a lubricant is warming up and flowing better after driving for a bit, quieting things down. Going to try a differential oil change at some point to see if that fixes it.

I have been searching everywhere but it seems there are no magnetic M24 x 1,5 (12 mm length) drain plugs available.
The propeller shaft center bearing was a Meyle, it should be OEM quality. The reason this was replaced not long ago was a sound, like a high pitch "chip-chip-chip" and then it was pretty obvious that it came from near the back of the car.
This new sound is "definitely" coming more from the front or middle. Every passenger are asking why there is a screaming sound from my comand screen or AC buttons. But I guess sounds can travel strange ways in a car and fool the ear.
As I understand the oil pump in the transmission is located in the front and therefore a whining pump would depend on RPM and not speed...




If it is confirmed to be rear differential I would just replace the 1Qt of oil and see..
Rebuilding those requires expertise and time to adjust gaps properly.
The results can be more disappointing than satisfying unless you get the right surgeon.




look at drainplugmagnets dot com
it took 6 weeks to ship and nearly $50... it's a vast improvement compared to steel particles circulating throughout.
.
Last edited by CaliBenzDriver; Nov 20, 2021 at 03:14 PM.
If it is confirmed to be rear differential I would just replace the 1Qt of oil and see..
Rebuilding those requires expertise and time to adjust gaps properly.
The results can be more disappointing than satisfying unless you get the right surgeon.
Thanks for the link, I guess this is the plug you ordered? 🙂




If your diff oil is super contaminated with metal, I'd consider doing ...:
- a second flush and
- clean the magnet,
- then be done: no extensive rebuild regardless.
Now I have replaced my differential oil and it was brown and and little clear, couldn't see any metal in it. It was also replaced seven years and 100 000 km ago.
No changes to the whining sound unfortunately...
What do you think I should do next? Try with another used propeller shaft? It would be quite cheap and easy.
Last edited by Bateman; Mar 17, 2022 at 01:21 PM.
Did you use an original support bearing?
I found information that the bearing can have different clearance, where CN is normal and C3 is a little bit different. According to a forum post the whining may be solved but using a C3 bearing.
That was going to be the next thing for me to try.





