‘11 E90 M3 needs new rear diff?!

[atlwillie]

Hi,

Long time reader, first time poster.

I have a 2011 E90 M3 with 34k miles on it. I’m the original owner and no mods on it. I took my car in for normal service and to have a rubbing sound checked out from the rear when making tight turns at slow speeds - thought it might just need a fluid change

They called me back and delivered bad news: a lot of metal shavings came out with the fluid and said that I’ve been grinding the diff and said I need a replacement. They asked “have you been driving aggressively or tracking it?” Of course I drive it aggressively! It’s an M3! Ive done an occasional doughnut and slide, no crazy drifting. I thought I had babied this car. How can this have caused a problem like this.

1) How can driving styles cause this and 2) if I have to replace is OEM the way to go?

Thanks!
Will

[Gossypiboma]

Theres always going to be some amount of metal on a diff drain plug and they are potentially just trying to squeeze you for more money. Sounds like normal clutch chatter at slow speeds. First replace the fluid with OEM fluid/friction modifier and see how it goes. Dont immediately jump to replacing the entire differential.

[DukeofAlexandria]

Originally Posted by Gossypiboma

Theres always going to be some amount of metal on a diff drain plug and they are potentially just trying to squeeze you for more money. Sounds like normal clutch chatter at slow speeds. First replace the fluid with OEM fluid/friction modifier and see how it goes. Dont immediately jump to replacing the entire differential.

This.^

Also, If you're savvy and mechanically inclined, raise it up and drop/open the pumpkin up yourself and see how much comes out. I'm betting it negligible and you can inspect for grinding/shearing areas once you clean it up.

Replace with high quality oil and additive and see if that helps. Did they say anything about it leaking? Super odd for this to happen on such a low mileage car.

-Duke

[tdott]

How often was the diff fluid changed if ever? Have anyone ever changed any of the seals? Improper pinion nut torque will cause pinion bearing failure.

I'd do a fluid change and make sure to use the correct fluid as the wrong one will cause some chatter.

If that doesn't help probably means one of the bearings has gone bad and you need rebuild.

[atlwillie]

I havent noticed any performance issues. I have no idea if the diff fluid has ever been changed. It’s whatever the dealer and now 3rd party mechanics have done following the basic schedule. Maybe the best thing is to replace fluid and see if noise goes away first?

[DukeofAlexandria]

Originally Posted by atlwillie

I havent noticed any performance issues. I have no idea if the diff fluid has ever been changed. It's whatever the dealer and now 3rd party mechanics have done following the basic schedule. Maybe the best thing is to replace fluid and see if noise goes away first?

Yeah, I'd go that route first. Make sure put an additive for gears into it and if you want, grab a sample and send it off for analysis.

-Duke

[bigjae1976]

The diff fluid should have been changed during the 1200 miles break in. Typical interval is 30k for the diff fluid. There are wet clutches inside limited slip diff so it needs some FM. I believe the G8X M3/4 and F9X M5 ask for 15k mile diff fluid services.

Possible that the diff was filled with SAF-XJ during the break in service. BMW would spec SAF-XJ+FM which has more FM in it if the customer was complaining about rear end noises at low speeds (There's an SI for it).

If its grinding, I doubt that new diff fluid would fix it but worth a try. The only other alternative is to rebuild the diff.

I've rebuilt four E46 M3 diffs so far. I'm about to start on an E93 M3 diff...how hard can it be? lol

[Davisca455]

This is the stuff that is being suggested.

[Helmsman]

Change with "Castrol Syntrax Limited Slip 75w-140" and give it a try. 10 min job on a lift, prepare with new drain plugs/o-rings.
This is OEM fluid, still with appropriate FM added but not more.

[tacoman]

Had the same noise last year. Thought it was my eibachs. Turns.out the diff had a leak. Gaskets etc replaced..new fluid too ...all is well since then brotha!

[roastbeef]

Originally Posted by Helmsman

Change with "Castrol Syntrax Limited Slip 75w-140" and give it a try. 10 min job on a lift, prepare with new drain plugs/o-rings.
This is OEM fluid, still with appropriate FM added but not more.

this.

[atlwillie]

Thanks, all. I had them cancel the new diff order and opting to try new fluid first. I’ve never heard any “grinding” just a sort of rubbing noise.

[tdott]

Originally Posted by atlwillie

I havent noticed any performance issues. I have no idea if the diff fluid has ever been changed. It’s whatever the dealer and now 3rd party mechanics have done following the basic schedule. Maybe the best thing is to replace fluid and see if noise goes away first?

Also I wouldn't trust some shop to make sure you are servicing things correctly. It's better to be an informed owner and know what needs to be done and when.

Esp when it comes to preventative maintenance, shops are usually only reactive when something goes wrong or they see something starting to wear/go bad.

[atlwillie]

Update: The shop said they’d drop the diff, open, and inspect it. If nothing was wrong, they’d eat the labor cost. I went over and saw for myself: both the diff and rear axle are f’d. Also, it looks like BMW San Francisco didn’t change the fluid after the 1200 mile break in! Not sure if that’s what caused this, but this is an expensive lesson. Yay.

[atlwillie]

Originally Posted by tdott

Also I wouldn't trust some shop to make sure you are servicing things correctly. It's better to be an informed owner and know what needs to be done and when.

Esp when it comes to preventative maintenance, shops are usually only reactive when something goes wrong or they see something starting to wear/go bad.

Lesson learned.

[Redd]

This is why I change all fluids the moment I buy a used car. Safer to assume its never been done.

[bigjae1976]

Any pics?

[shimmy23]

regardless of the 1200mile service being performed, 34k miles for a diff to fail is not normal.

[tdott]

Originally Posted by shimmy23

regardless of the 1200mile service being performed, 34k miles for a diff to fail is not normal.

It's also more than 10 yrs old.

[Ubersmooth]

My diff failed last summer. I found diffsonline to be the best option. You can have it built to your desired specs as well. A 4.10 differential would fit the M3 nicely 👍🏽

[amrazM]

Originally Posted by Ubersmooth

My diff failed last summer. I found diffsonline to be the best option. You can have it built to your desired specs as well. A 4.10 differential would fit the M3 nicely 👍🏽

agreed, i had to source a diff for my manual swap. when its all said and done its not a bad deal to source a diff from dan, his prices are fair for a refreshed diff.