[DaanBMW]

My wife noticed an oil leak under the car... from the rear. Went to my mechanic: my driver's side half-shaft is pushing out of the rear differential. See below image, or attached PDF (pics are not mine but mine was almost the exact same).

WTF ? How is this possible ? I had an LSD installed by same mechanic 1/2 a year ago, and everything was replaced by the book: the seals, the lock rings (items 13 + 14 in realoem diagram here). Even the Torx screws that hold the half-shafts.

1. 1st q: Is this a bad install issue ? Or does this happen out of the blue ? From what I have searched not much on e90post here, found 1 post on bimmerfest, that's about it. I can't imagine the lock ring breaking, and there is no updated/upgraded part fot it. I also recall right after the LSD install I went to my mechanic and one of the half-shafts was pushed out more then the other... but not this much, it was like 1.5-2" from the diff face.
   
   
2. 2nd q: How to fix ? Mechanic did bang it back in and we topped fluid off. But I think this will happen again. Replace lock ring ? Half-shaft seal too ? On both sides, or just driver ?
   
   
3. 3rd q (stupid q ?): Does the lock ring come out with the output flange just by pulling ? Do you have to open the diff case ?

[mike-y]

huh. never have seen that before. it might have been an installation issue, but it doesn't make sense that it took 6 months to pop out.

since you already had it put back in, keep an eye on it. I'd probably want to have it looked at to make sure the lock ring was still in place and not broken, and everything else was okay. The other side should be fine though, I doubt you'd need to worry about it.

the lock ring should come out with the shaft if you pull it out... unless it has broken off and fallen into the diff case.

[DaanBMW]

Originally Posted by mike-y

huh. never have seen that before. it might have been an installation issue, but it doesn't make sense that it took 6 months to pop out.

since you already had it put back in, keep an eye on it. I'd probably want to have it looked at to make sure the lock ring was still in place and not broken, and everything else was okay. The other side should be fine though, I doubt you'd need to worry about it.

the lock ring should come out with the shaft if you pull it out... unless it has broken off and fallen into the diff case.

Well, it didn't really take 6 months to pop out. It did pop out before as I mentioned, but not so far, and probably that is why no oil leaks until now.

Since the lock ring comes out with the shaft if you pull it, what exactly _is_ holding it in against the diff case ? This popping out is either normal - which according to my understanding and my mechanic it is not - or not normal, but then something should keep the darn stubs in, and if not the lock ring then what ?

[mike-y]

the ring sits in a groove on the shaft, but it's a bit loose has a groove so it can be compressed. It's outside diameter is a little larger than the diff socket. when you press the shaft in the diff, the ring compresses to fit inside the socket, and then "pops" back to it's original shape once it's all the way inside the socket to lock the shaft in place.

if the ring isn't seated right, it may allow the shaft to pop out. or if the ring is weak, it may compress to easily and allow the shaft to pop out when you don't want it to. if it breaks, the shaft can come out easily, and the ring comes out with the shaft in pieces, though there is a chance some pieces can fall into the diff case

here's a pic

[Rockyca]

The half shafts aren't really held in by much. You just tap them out from what I remember. Get a new snap ring and reinsert. You should be good to go!

[DaanBMW]

That pic helps, thanks mike-y ! From the sounds of it the rings come out easily - so even is seated propely they can still become unseated ? Since there are so few instances I found this to happen in the user coomunity, not sure why it is happening on mine...

Slowly concluding that since my lock rings were OEM new, chances are they either broke or didn't get pushed far enough to snap & secure ?

So just re-do just driver side ? Replace lock ring, seal. Anything else ? I think I'll need to disconnect the half-shaft from the output flange, so another round of ribbed torx screw, don't think it be done with them connected.

[DaanBMW]

OK, got the half-shaft disconnected, the flange out, and the seal. The only wrong thing we noticed was that the lock ring was too much in the groove, instead of popping out just a bit (it's a C-shaped piece of steel wire). It could spin freely so it wasn't jammed. Replaced the lock ring - which now does pop out beyond the OD of the spline shaft of the flange - and the shaft seal, put everything back, vacuumed the diff oil and filled with fresh LSD oil. Time will tell I guess...

So as I see it this lock ring did not do it's job because we found it inside the groove not popping out. But I can see 2 scenarios: (1) ring was not proper size, albeit both were OEM; (2) the ring was popping out when we installed is, but because the mechanic did not push the flange far enough it stayed compressed and over time fatigued and lost it's correct shape. Could be the seal not seated deep enough or the dust cover cocked, or simply not driven in enough.

Anyone have any other thoughts ?

[davidwarren]

I just noticed the exact same thing. I pushed the output shaft back into the diff. So I can remove the half shaft, pull the output, and replace the c-clip without opening the diff?

[DaanBMW]

Originally Posted by davidwarren

I just noticed the exact same thing. I pushed the output shaft back into the diff. So I can remove the half shaft, pull the output, and replace the c-clip without opening the diff?

Yes, no need to open up the diff. C-clip is really all you really need, but here is what I replaced as well (note all is 2x showing, so you only need 1/2 for only 1 output shaft):

1x drain/fill plug Screw plug with O-ring M22X1,5-ZNS3 33117525064
2x diff to half-shafts Shaft seal with lock ring (90x44x10) 33107505604
12x diff to half-shafts Torx screw with ribs M10X43 ZNS3 33207572716
2x diff to half-shafts Dust guard ring, inner (D=60) 33131214298
2x diff to half-shafts Dust guard ring, outer (D=68,8) 33131428097

Was also on the list but crossed-out meaning I did not replace it -> incorrect. This is C-clip, I must've had the mechanic get it so we don't play warranty games. THIS IS THE PART YOU REALLY NEED:

2x diff to half-shafts Lock ring (168K/L 188K/L) 33131214961

[davidwarren]

Originally Posted by DaanBMW

Yes, no need to open up the diff. C-clip is really all you really need, but here is what I replaced as well (note all is 2x showing, so you only need 1/2 for only 1 output shaft):

1x drain/fill plug Screw plug with O-ring M22X1,5-ZNS3 33117525064
2x diff to half-shafts Shaft seal with lock ring (90x44x10) 33107505604
12x diff to half-shafts Torx screw with ribs M10X43 ZNS3 33207572716
2x diff to half-shafts Dust guard ring, inner (D=60) 33131214298
2x diff to half-shafts Dust guard ring, outer (D=68,8) 33131428097

Was also on the list but crossed-out meaning I did not replace it -> incorrect. This is C-clip, I must've had the mechanic get it so we don't play warranty games. THIS IS THE PART YOU REALLY NEED:

2x diff to half-shafts Lock ring (168K/L 188K/L) 33131214961

Thanks!

[mp-E46]

I have replaced the C-clip twice and it still keeps popping out. I may need to replace the half shaft.