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.

[M4Q]

@xwilkinx - did you replace the diff yourself or took it to a shop? I’m in the process of changing mine too but I’m doing it at home myself and was wondering if there are any technical service manuals from BMW for this job. I have the diff out and everything is ready for new parts to go in but I fear I may skip some step when installing the new diff in and end up messing that one up.

[b_w.]

Originally Posted by M4Q

@xwilkinx - did you replace the diff yourself or took it to a shop? I’m in the process of changing mine too but I’m doing it at home myself and was wondering if there are any technical service manuals from BMW for this job. I have the diff out and everything is ready for new parts to go in but I fear I may skip some step when installing the new diff in and end up messing that one up.

Ista is your answer

[j2dad5389]

How does something like this even happen?

[xwilkinx]

Originally Posted by j2dad5389

How does something like this even happen?

I believe incorrect oil/amount or the the rear diff service wasn’t actually done @ 50k like I was told. Less than 500ml was drained when it should take a little over 1L.

I now check my rear diff fluid regularly!

[Tommix]

I'm guessing that the reason for that failure was that there was a manufacturing defect in the ball bearing.

[N1rve]

Originally Posted by Tommix

I'm guessing that the reason for that failure was that there was a manufacturing defect in the ball bearing.

I don’t think so. I think it’s due to lack of fluid. OP only drained out about like less than a 16.9 ounce water bottle. Supposed to be almost 2 liters in there which is about 33 ounces. It’s missing a lot of fluid.

[Tommix]

Originally Posted by N1rve

I don’t think so. I think it’s due to lack of fluid. OP only drained out about like less than a 16.9 ounce water bottle. Supposed to be almost 2 liters in there which is about 33 ounces. It’s missing a lot of fluid.

This is entirely possible. I would like to see what condition the rear friction plates are.

[N1rve]

Originally Posted by xwilkinx

I believe incorrect oil/amount or the the rear diff service wasn’t actually done @ 50k like I was told. Less than 500ml was drained when it should take a little over 1L.

I now check my rear diff fluid regularly!

Was your rear diff originally leaking or seeping from the seals?

[xwilkinx]

Originally Posted by N1rve

Was your rear diff originally leaking or seeping from the seals?

No, there was no evidence of any leaks.