differential advice please

[typhoon320i]

(Bare with me as I have never worked on a diff before)
I don't know the proper terms for everything

I have pulled the diff out of my car. It's my understanding it is not original to the car. I have a 320i but I counted the teeth in this, and it is 43:11 so... from my Haynes, it looks like it is from a 320
I am only pulling it to replace the oil seals as I think it works fine, but leaky.
I really don't want to rebuild the whole thing, as this is my first encounter with a diff, and I think it works fine.

Questions:
Will I be able to pull out the half shaft flanges to just replace the side seals without the insides coming apart?
I'm guessing the front pinion, or conical gear, can all stay in while I replace the pinion seal, correct?
Also I do understand if you undo that front nut you need to count threads and index to not over or under tighten and ruin the bearings, and crush sleeve.
First step: My Hayes manual talks about removing the "flange locking circlip" from the center to get the side shafts out, but I don't see one (see picture)
How do I get the side shafts out? should I do them one at a time to keep the insides intact?
Thanks for any help.
diff1.jpgdiff2.jpg

[amarino]

I've usually just used a big flat screwdriver (or crowbar) to pop the flanges out from the outside. Like the 3rd picture here: https://www.bimmerforums.com/forum/s...ld-(Pic-heavy)

[maxitoman007]

I recently did some diff work (Racing Diffs LSD conversion kit install) on my 79 320i so I can answer a couple of your questions. I didn't do any pinion work so someone else will have to chime in for that.

Will I be able to pull out the half shaft flanges to just replace the side seals without the insides coming apart?

Sort of. Those side flanges hold the outer bearing races for the bearings on the outside of the diff, so when you pull those flanges off, the diff carrier will be loose inside the diff housing but nothing will fall apart. Once you replace the seals in the flanges you'll just have to guide the bearings on the outside of the diff carrier into the races on the flanges during installation.

My Hayes manual talks about removing the "flange locking circlip" from the center to get the side shafts out, but I don't see one (see picture)
How do I get the side shafts out? should I do them one at a time to keep the insides intact?

See amarino's reply above. The Haynes manual was wrong for my diff too. There are no retaining circlips in that diff, simply pry the drive flanges out. There is a sort of metal spring retainer that holds each shaft inside so it will sorta pop out once you've pried hard enough. Instead of applying a constant prying force, I found that hitting the prying tool with a sudden force (think of popping them out) worked best. When reinstalling you'll also want to make sure you feel them pop back in.

As for doing one side at a time, that's not really important. Once one side is removed, the carrier will kinda sag on that side because of there being no outer race for the outer diff bearing. As mentioned above, having both removed will just leave the carrier loose in the case. Then it's just a matter of reinstalling the flanges properly ensuring the bearings on the carrier go back into the races.

[typhoon320i]

Thanks so much for the input. I will probably be back with more questions if I run into any issues.

[typhoon320i]

I've usually just used a big flat screwdriver (or crowbar) to pop the flanges out from the outside. Like the 3rd picture here: https://www.bimmerforums.com/forum/s...ld-(Pic-heavy)

Thanks for the link. Walkthrough like this is so helpful. I searched Youtube for this kind of thing, but none to an E21, that I could find.
MrGumby was replacing the bearings too, but do the side bearing caps need to come out, if you are just doing the seal? (either removal or install)

[pofo]

its come apart very easy just make sure you keep the sims organized and know where they came from. Its kinda hard to mess it up to be honest.

[maxitoman007]

Thanks for the link. Walkthrough like this is so helpful. I searched Youtube for this kind of thing, but none to an E21, that I could find.
MrGumby was replacing the bearings too, but do the side bearing caps need to come out, if you are just doing the seal? (either removal or install)

In theory you could do it without pulling the flanges, but I think it is a safer bet to take them off. With them off its easier to correct errors such as pushing the seal in too far. You're also supposed to pack grease between the 2 lips of the seal once installed which may be tough with the flanges still in as the lips face inwards.

[autox320]

(Bare with me as I have never worked on a diff before)
I don't know the proper terms for everything

I have pulled the diff out of my car. It's my understanding it is not original to the car. I have a 320i but I counted the teeth in this, and it is 43:11 so... from my Haynes, it looks like it is from a 320
I am only pulling it to replace the oil seals as I think it works fine, but leaky.
I really don't want to rebuild the whole thing, as this is my first encounter with a diff, and I think it works fine.

Questions:
Will I be able to pull out the half shaft flanges to just replace the side seals without the insides coming apart?
I'm guessing the front pinion, or conical gear, can all stay in while I replace the pinion seal, correct?
Also I do understand if you undo that front nut you need to count threads and index to not over or under tighten and ruin the bearings, and crush sleeve.
First step: My Hayes manual talks about removing the "flange locking circlip" from the center to get the side shafts out, but I don't see one (see picture)
How do I get the side shafts out? should I do them one at a time to keep the insides intact?
Thanks for any help.
diff1.jpgdiff2.jpg

Side seals are straight forward as others mentioned. Shafts knock out easily enough. There are also thin o-rings on the perimeter of the side flanges if knock those out as well.

Pinion; yes mark a reference mark across the nose of the pinion and nut. If overtighten it will crush the sleeve for pinion preload. Usually it's not much issue unless using a impact gun. Torque by hand very tight with some loctite. It takes a lot of force to crush the sleeve by hand so very very unlikely unless using a long leverage bar and have the flange of the diff in a heavy vise. Flange spec tighten should be around I want to say it's 108 ft-lbs

Not sure what seals your using but I like Timken from Rockauto. Least I know I'll get something decent in a timken box. I put black ultra rtv with a finger around the outer perimeter of each seal before knocking it in. Makes it weep free. For military guys ie no class one leaks

[typhoon320i]

Thanks guys...helpful info.

[Tom D]

to set the record straight.....

early E21 diffs do have C-clips holding the output drive flanges and have to be removed from within the diff. later diffs you just pry up on the flanges.

[maxitoman007]

early E21 diffs do have C-clips holding the output drive flanges and have to be removed from within the diff. later diffs you just pry up on the flanges.

I'm thinking the transition year is somewhere around the 77 mark? My 79 didn't have them.

[Tom D]

I'm thinking the transition year is somewhere around the 77 mark? My 79 didn't have them.

https://www.bimmerforums.com/forum/s...eptions-debunk

[maxitoman007]

https://www.bimmerforums.com/forum/s...eptions-debunk

Beautiful.

[typhoon320i]

Can anybody help? I am deducing that the pinion seal I'm replacing goes under this metal donut, around the shaft, but I have no idea how this is supposed to be removed. Do I pry a lip up perhaps where my screwdriver tip is? Anybody done this?
Haynes just says: Prise out the oil seal and press in a new one.....and no pictures.....helpful

Pinion seal2.jpg

[typhoon320i]

I see this photo shows where the housing ends and the seal begins. There does seem to be a metal top on the seal. (This might be the OE seal for the diff.) should I drill into it, and pry it up with a nail, or smack it down with a punch to loosen it? I don't have a seal puller, but I could get one if it's recommended.

2011.02.20.jpg

[mjweimer]

Can anybody help? I am deducing that the pinion seal I'm replacing goes under this metal donut, around the shaft, but I have no idea how this is supposed to be removed. Do I pry a lip up perhaps where my screwdriver tip is? Anybody done this?
Haynes just says: Prise out the oil seal and press in a new one.....and no pictures.....helpful

Pinion seal2.jpg

That should be the pinion seal you are touching with the screwdriver. When you removed the drive flange there should have been a dust shield that came off along with it, exposing that seal.

https://www.realoem.com/bmw/enUS/sho...diagId=33_0598


You can remove the seal several ways; the nail method can work really well (see video link below @3:14), cross two longer screwdrivers under the edge of the inner seal, leverage them on the outer case and push down gently to start it out of the bore working your way around the seal using the same method, or drill and use a slide hammer made for seal removal. I don't know if the punch method will work on this particular seal - depends on the gap between the seal and the bearing and you don't want to accidentally push it further in the bore. Others might have some additional tricks.

https://www.youtube.com/watch?v=OLG3SuZ70uM

Just make sure to not damage the machined surface of the differential case (outer diameter) where the seal sits and check the fit of the drive flange on the splines before fitting the new seal. Sometimes the splines get a burr that needs some polishing and it is much easier to check fit and correct without a new seal in place.

[typhoon320i]

Yes, the dust shield did come off with the flange, thanks.
I think I'll wait until my new seal gets here, and lay it on top, to be sure of exactly where the old one ends. Thanks for the advice.

[typhoon320i]

Question: I have a new paper gasket for the rear diff cover. Should I put a bead of gasket maker on it? Or just use it with no sealant added?

[pofo]

yes you need some gasket maker

[Bimmerod]

Here's a cool E21 rear differential restoration video. There's hope for all of our rusty diffs out there

https://youtu.be/qSG_-B1U3fI

Bimmerod

[typhoon320i]

I'll have to watch that video. It was posted after I already started mine.

Additional question: what is the torque spec for the diff drain and fill plug? Haynes doesn't list it. ........edit (I since heard 35 Ft. Lbs. with the aluminum sealing washers)

Mine's almost ready to reinstall:
k.jpg