Differential Refresh, what's needed?

[Earendil]

I've found lots of threads on rebuilding differentials (and some neat pictures too), but I just want to know what is needed to refresh a differential such that the chances of it leaking are lowered.

The scenario is that I have a S4.10 sitting on a bench that will go into the car when I do the clutch. Since the weather sucks, I thought I'd go ahead and find some good indoor projects. I have no reason to believe there is anything wrong with the seals on this diff, but if they can re replaced for under $20, why not? I have the time...

But I can't figure out what needs replacing! Even pelican parts, which has seal kits for just about everything, doesn't seem to sell any differential seals. So what am I missing here?

Thanks for any points, thanks even more for part numbers :D

[ChaseN]

http://realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=33_0116&hg=33&fg=10

http://realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=33_0124&hg=33&fg=10

http://realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=33_1493&hg=33&fg=10

#3 (x2) in the first image, #3, 6 (x2), and 9 in the second image, and #5 in the third image are all your seals. You'll probably need a #3 in the third image too as you might mangle it up getting it out.

One rule I go by with non-critical seals though, is if it isn't broke, don't fix it...

[blefevre]

#8 in the first image too (2x)
#2 first image (2x) isn't bad either
Do the diff bushing too
#16 picture 2

[Earendil]

http://realoem.com/bmw/showparts.do?...16&hg=33&fg=10

http://realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=33_0124&hg=33&fg=10

http://realoem.com/bmw/showparts.do?model=1113&mospid=47309&btnr=33_1493&hg=33&fg=10

#3 (x2) in the first image, #3, 6 (x2), and 9 in the second image, and #5 in the third image are all your seals. You'll probably need a #3 in the third image too as you might mangle it up getting it out.

One rule I go by with non-critical seals though, is if it isn't broke, don't fix it...

If I weren't sick, and you weren't male, I'd kiss you.

Which of these would you call "none critical" ? Or are all of them considered such? I picked up the diff from a guy that pulled it from a some other car, and never used it. It's rather clean, but I have no clue how good the seals are because I haven't seen it after being stressed.

[blefevre]

I left my input seals alone so I didn't have to deal with the huge torque and backlash. The dust covers on the output flanges aren't critical. Just make sure to get the output u-cups and o-rings, cover gasket and bushing. Those are the important ones. It's super easy work too with the diff out of the car.

[ChaseN]

#8 in the first image too (2x)
#2 first image (2x) isn't bad either
Do the diff bushing too
#16 picture 2

Diff bushing is #13 in the 2nd pic, otherwise good recomendations.

As far as non-critical seals, if your diff isn't leaking at all, I'd leave out the input shaft seal (#5 3rd image), it can be a bit of a bitch without the proper tools.

Also if you don't want to spring for a diff bushing, 3M window weld in the open webbed areas of your current bushing (assuming its in decent condition) works really well, and you can keep the tube and use it on all sorts of different things...kind of a ghetto way of doing it, but its an option

[iamsam]

I am bumping this thread. It seems my 4.10 LSD started pissing out the front where the driveshaft goes in. (input seal?)

And above someone mentions it is a PITA to replace w/o proper tools. What proper tools? Where do I get them?

[iamsam]

Also, found this, this guy uses a special tool to remove the output seals. http://www.r3vlimited.com/board/showthread.php?t=71115&

[blefevre]

1. It is torqued to a crazy high value. 2 you need to set/check the backlash with a proper gauge.

[iamsam]

1. It is torqued to a crazy high value. 2 you need to set/check the backlash with a proper gauge.

I have an impact gun, and what backlash? what gauge? You mean a thickness gauge? I heard that you just replace the crush washer or whatever and simply re-tighten the bolt to the original position, which you mark before you start...

I have two 4.10 LSDs that need various things, and it would be awesome to just replace all seals/bearings in both at once.

[blefevre]

You will need to set pinion bearing drag, usually a really low value, so you have the correct drag when you install new parts.

Backlash gauge. I believe there are shims in there that move the parts around correctly to get the correct backlash.


You "could" mark the position of the old bolt and new but that is a really ghetto way of doing it. You should always torque properly, especially when dealing with bearing drag and seals.

Most of this is taken from Jeep diffs, but I am 99% sure E30's function the same.

[iamsam]

So in this pic:



ALL those parts are needed, as in # 9 and 7 sit behind #8, and #9 is the crush shim?

So in other words, if I wanted to replace all the bearings and seals in the diff w/o removing the actual diff from the housing, what parts are needed? 2,3,5,6,7,8,9 from the above pic and 2,3,5,8,9 from the below pic?

[blefevre]

So I looked in the manual. It only talks about replacing the input SEAL, which you can just line the marks up on the bolt then replace the seal and tighten back to the original location and you should be fine. It will be over 200 ft/lbs. It doesn't mention specifics on replacing the input bearings.

The output is easy, you listed the correct parts. I did everything except the bearings because the diff was only 74k miles old. I didn't touch the input seal or bearings but I did check backlash and it was well within spec.

If you need more specifics on the input BEARINGS, you will have to do some searching to see how to set backlash and proper drag.

In the first picture #2 is just a dust cover.

[iamsam]

So I took the input shaft bolt off my bad diff today, just to get familiar, before buying parts for my good diff. So the bolt came off waaaay too easily, I put the impact gun on there and with a super short burst, like one second maybe, the big bolt was completely loose, and I took it off the rest of the way with my fingers.

So I got the seal out w/ a screwdriver (not that hard), I could see the bearing. However, all attempts to take the bearing out failed, short of destroying the bearing. does this come out through the back after removing the LSD unit?

Thanks

[Wanganstyle]

1. It is torqued to a crazy high value. 2 you need to set/check the backlash with a proper gauge.

is NOT torqued to crazy high value.

here is the FACTORY BMW procedure :)

http://tis.spaghetticoder.org/s/view.pl?1/00/50/34