Rear differential failure (pics included)

[xwilkinx]

A few weeks ago I noticed a sound while driving coming from the rear that sounded like a rock/nail stuck in the tire. Within 10 minutes, the sound became much louder at which I stopped driving. No abnormal vibrations or power loss.

Here's a vid of the sound that I recorded while driving about 20kmh (12mph): https://youtube.com/shorts/wV5ceRpREz4

The sound would immediately stop when shifting into neutral while coasting. When I jacked up the car and put it in gear, the noise did not happen. I didn't see anything visually out of the ordinary.

I towed the car to a local BMW specialist and they identified the sound to be coming from the rear diff. When they drained the fluid, ball bearings came out sheared in half!

Destroyed ball bearings and metal filings:


Fluid drained:


I had the rear diff replaced with a lower mileage one along with all new bushings.

The car had about 120,000 kms (74,000 miles) on it at the time. Last documented rear diff flush was at 80,000 kms (50,000 miles).

[jaylazy2020]

Sounds worrying. I’ve 83km on mine and getting new fluid today when they fix the right hand side seal that is leaking.

Did you have any clunks on 1st to 2nd or 3rd to 2nd since you’ve owned the car?

[xwilkinx]

Originally Posted by jaylazy2020

Sounds worrying. I’ve 83km on mine and getting new fluid today when they fix the right hand side seal that is leaking.

Did you have any clunks on 1st to 2nd or 3rd to 2nd since you’ve owned the car?

No clunks at all before the failure, the car felt perfectly fine leading up to it!

[WarMachineM3]

Buy a used rear diff and have it replaced. Or a new one from getbmwparts.

[xwilkinx]

Originally Posted by WarMachineM3

Buy a used rear diff and have it replaced. Or a new one from getbmwparts.

I found a low mileage one! Already replaced, just thought I'd share this.

[fivaxis]

I have only 65k on my 2017 m4 and my differential is bad, it makes a high pitched shhhh sound while driving. BMW says the diff bearings are bad and they want like 8500 to install a new one in ha ha. I'm probably gonna have a used one put in at an independent shop.

[xwilkinx]

Originally Posted by fivaxis

I have only 65k on my 2017 m4 and my differential is bad, it makes a high pitched shhhh sound while driving. BMW says the diff bearings are bad and they want like 8500 to install a new one in ha ha. I'm probably gonna have a used one put in at an independent shop.

Avoid that dealer! You can find a good used diff for under $1k

[FatHulk]

Just changed my rear diff fluid and it was not nearly as dark as yours. Although only 15km. Noticed it was leaking so I need to replace the gasket.