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Discussion Starter · #1 ·
I have a leak on my passenger's side output shaft on the differential in my 2003 M3. I also have the infamous clunk when shifting gears and it seems to be getting worse. Looks like I'll have to drop the differential to replace the bushings to hopefully fix the clunk and while I have it out, I will replace the output shaft seal also to fix the leak.

Is there other recommended maintenance that I should do while I have it out? Should I do both output shaft seals and the input seal also?

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If the input seal's not leaking and the diff is quiet, I would not touch it.

If it starts leaking later, it's easy to do with the diff in the car-
easy meaning you only have to remove the saddle bracket and
the driveshaft...

Change the fluid, of course.

t
 

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Discussion Starter · #3 ·
Awesome, I ended up ordering 2 output shaft seals and didn't get the input seal since it looks like it's a harder job and it's not leaking. I already changed the fluid just to see if it would help with the clunk and I don't think I'll lose too much if I just replace the output shaft seals so I'll top it off when done. Thanks

If the input seal's not leaking and the diff is quiet, I would not touch it.

If it starts leaking later, it's easy to do with the diff in the car-
easy meaning you only have to remove the saddle bracket and
the driveshaft...

Change the fluid, of course.

t
 

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'01 320Ci manual
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I'd do the seals that are leaking, if the other decides to leak someday I'll leave it for then
 

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OEM ///PLUS
2003 M3 6MT Slicktop
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23,785 Posts
i haven’t seen a correlation on one seal going out meaning the other is soon. in the case of input seal I would not touch it if it’s not leaking.
as for your M3 diff bushings do the front, it’s a pain to access and it goes out. I would use OEM on that one, it’s a beefy solid mount. as for the rear differential mount, they’re pressed in the cover. BMW doesn’t sell replacements. only a new cover. so your options there are: 1) new cover 2) poly bushings for cover 3) E36 M3 diff cover bushings.
poly will add some NVH and ppl sometimes crack cover during press-out/press-in. E36 M3 bushings are not as firm as E46 M3.
 

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Discussion Starter · #6 ·
i haven’t seen a correlation on one seal going out meaning the other is soon. in the case of input seal I would not touch it if it’s not leaking.
as for your M3 diff bushings do the front, it’s a pain to access and it goes out. I would use OEM on that one, it’s a beefy solid mount. as for the rear differential mount, they’re pressed in the cover. BMW doesn’t sell replacements. only a new cover. so your options there are: 1) new cover 2) poly bushings for cover 3) E36 M3 diff cover bushings.
poly will add some NVH and ppl sometimes crack cover during press-out/press-in. E36 M3 bushings are not as firm as E46 M3.
This is great info, thanks. I noticed that FCPeuro sells a Revshift brand of dif bushings that claim to be OEM spec for stiffness and I ordered those. Glad to hear that just because one seal is bad doesn't mean the other will go out soon. I'll keep the extra seal as a backup and won't touch the input shaft seal.

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2003 M3 6MT Slicktop
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This is great info, thanks. I noticed that FCPeuro sells a Revshift brand of dif bushings that claim to be OEM spec for stiffness and I ordered those. Glad to hear that just because one seal is bad doesn't mean the other will go out soon. I'll keep the extra seal as a backup and won't touch the input shaft seal.
while you have the diff out and already have both output flange seals, may as well install. it’s fairly easy. just verify it’s properly seated before reinstalling diff. the right side diff seal seems to be the one that leaks from other reports. it was lightly leaking on mine before I replaced it years ago. as far as seals go, it’s actually somewhat kinda fun to install compared to others on the car.
some ppl mistake the oil “misting” from the top diff vent hole as a leak from the seal. but that flange seal absolutely can go out.
 
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