Got a diff here that has seen enough

[turbodan]

I swapped this 3.25S out of the turbo 528 at the request of the new owner. Its been in the garage sitting around for a few days until I feel like taking it out and burying it in the neighbors yard. While looking around it in the garage for something else I noticed the marks in the case like the ring gear had been hitting it. This is surely impossible especially since the diff was still operational without any strange noises or severe leakage.



The source of the debris that caused these gouges was the limited slip unit, which has very few bolts remaining in place. Several are missing, some are broken and the rest are loose. The flange these bolts tighten into is cracked and broken in a few spots as well.



The ring and pinion seem to have been chewing and spitting out metallic debris for some time but show no troubling wear or damage. At some point though this has got to tear them up. The fluid that came out looked pretty bad and I guess this explains it. There was like five ground up bolts mixed into the 1.2 quarts of GL-5.

[Kyle in NO]

That's pretty awesome. When I removed the S3.25 from my turbo 533i, it had the head of one of the ring gear retaining bolts laying in the bottom. Hmmm.

[turbodan]

Its just another thing to keep an eye on I guess. I know I beat the hell out of this diff and I'm sure the last year with its new owner wasn't any less brutal. Probably had 200k miles on it before I even got it in the first place.

[Jelmer538i]

I'm glad we have so many 210 diffs overhere in Europe!

[derrith]

Seen this happen in spec e30 diffs and e36 m3 track cars. Also found them all finger tight on the 188mm 3,73 I had in my M5 for a while when I swapped for 4,10. I now pull the cover and check them when I do a fluid change on that car.

[athayer187]

When I rebuilt the limited slip on my 535is (that sees significant track duty), everything internal got red Loctite. Unfortunately, I've seen this on BMW 188 diffs as well. Crazy.

[Cooperman]

I think I will red loctite the bolts on that diff I got from Kyle.

(I knew what I was getting.)

[Kyle in NO]

I think I will red loctite the bolts on that diff I got from Kyle.

(I knew what I was getting.)

If you find that the diff itself is damaged, please let me know and I will give you a full refund!

[Cooperman]

You sold it to me with that understanding. No worries. I was just trying to be funny.

I will try harder.

I think I will red loctite the bolts on that diff I got from Kyle.

(I knew what I was getting.)

If you find that the diff itself is damaged, please let me know and I will give you a full refund!

[Kyle in NO]

I know you were. Just check the part shown in turbodan's pic. If it's screwed, let me know.

[Jeremy]

I wonder if running synthetic fluid would exacerbate this. There have been anecdotal stories over the years of synthetic gear lubes contributing to diff failure. I never put much stock in them, but if the bolts backing out is a real possibility, then I suppose it's possible that synthetic gear lube could make this more likely.

What's the torque spec for those fasteners? Is it something specific or is it just "guttentight"?