e36 lsd internals fit into e21 case

[joey79]

i got about 8 e36 LSD for sale $250 plus shipping..

i will try and do one myself and see how it turn out. very good idea by the way. awsome job.

edit : my question to you now, is the half shaft. are they going to need any modifications ? and is the e21 half shaft gonna fit the e36 internal diff?

i will assume the half shaft will need to be cut and shorten like an inch or 2. or no ?

Are your e36 diffs small case (318i or 320i)? The medium case internals won't work.

Regarding the half shafts. I don't see why they'd have to be shortened, since I'm using the e21 output flanges. The portion of the output flange that fits inside the diff is identical to the e36's, diameter, splines, snap ring groove.

[BIMMERBOYZ]

May I ask what is the point? The advantage of doing this.

[BaronOfIpanema]

Seems like its a great way to change your ratio fer cheap, and beef up your diff at the same time.

[joey79]

May I ask what is the point? The advantage of doing this.

My 323i currently has a whiney 3.91 open diff. After this, it will hopefully have a non-whining 3.45 lsd, for the price of $75(what I paid for the e36 diff).

[jrcook320]

This is a great thread, it should be added to the faq.

To answer the question of why,

Pros:
-commonly available 3.45 ratio, easier to find than an e21 3.45 LSD (super rare as it was only available as an option on 323i's), or 3.45 open
-cheaper than an e21 3.45 LSD
-might even be cheaper than an e21 3.91 LSD, which is "common" compared to the 3.91 but still getting harder to find
-other benefits might be an improved LSD design with more clutches (for longevity) or different ramp angles, etc. this is unknown to me, just a guess.

nuetral:
-The gear sets shouldn't be any stronger than the e21 diff as they're still the same 168mm
-The LSD probably isn't any stronger and it likely uses the same size clutch as the e21 diff
-The e36 offers the same 25% lockup as the e21 LSD

Cons:
-individual replacement components for the e36 318i LSD are not available, the LSD unit is sold as a whole so unless you work some majic and find parts from the BMW parts bin that fit, the LSD is not rebuildable. The e21 LSD is still rebuildable.
-added work to swap pinion and ring gear into a new case which involves completely rebuilding the diff, setting torque to turn & gear lash. Not a problem, but outside the scope of most home mechanics. It would take less work to swap an LSD carrier into a 3.45 open.

[RetroBeemer]

Nice work. Hope you don't mind but I pasted your post on the UK forum as I know a couple of guys looking to do this conversion.

[sonomaGTLN2]

Definitely a sweet thread. Before investing in a donor E36 diff I'd like to see if any development is needed on the pinion side. What are the lash/gear mesh specs for the E36 diff? And to be certain, this is only off an E36 318i non-hatchback?

[E21Adam]

Definitely a sweet thread. Before investing in a donor E36 diff I'd like to see if any development is needed on the pinion side. What are the lash/gear mesh specs for the E36 diff? And to be certain, this is only off an E36 318i non-hatchback?

The 318ti used an e30 small case diff. The e36 diff is different, at least externally. That said, after this I wonder how similar the internals are between the e30 and e36. I've heard that small case e30 internals can be made to fit into the e21 diff. Since the 318ti also uses a 3.45:1 final drive ratio (4.45:1 for auto), you could hypothetically fit a 3.45:1 out of a ti to fit an e21 with the same effect as the e36 318i diff. A 318ti LSD goes for about as much as an e21 LSD though (they're pretty rare).

[joey79]

Pinions are interchangeable. First post updated with pictures.

[pommeree]

Pinions are interchangeable. First post updated with pictures.

Cool!
Next question.
What's involved in removing the carrier bearings?
Can they be removed allowing placement of the LSD unit without shaving the case and then refitted through the sides?
Thanks!

Answer: "Don't you think I thought of that before taking a die grinder to my case!?"

Response: No, seriously. What part of getting those bearings off makes for such an obstacle?

[joey79]

The case has to be shaved. The lsd unit and ring gear are the binding points, not the bearings.

[thowey]

sorry to resurrect an old thread but can you just swap the e36 3.45 gears on a e21 3.91LSD carrier? you've already stated the pinion is the same, what about the ring gear?

[milotrain]

They should be the same I think, but aren't e21 3.45 opens easy to find?

[E21fun]

yeh the point was to use the other ratios since the e21 limits you to 3.45 and 3.91

[thowey]

i've only found 3.91s

[joey79]

Finally got the diff assembled, after waiting for parts/tools/etc. It all went together smoothly and feels good while turning it. Gear contact pattern looks good. I don't have a way of precisely measuring backlash, but it feels like every other good BMW diff I've felt. A tiny bit of play when rotating the output flanges back and forth. The moment of truth will come this weekend when I get it installed and beat it like it stole something.

[Beemer Tech]

-other benefits might be an improved LSD design with more clutches (for longevity) or different ramp angles, etc. this is unknown to me, just a guess.

Cons:
-individual replacement components for the e36 318i LSD are not available, the LSD unit is sold as a whole so unless you work some majic and find parts from the BMW parts bin that fit, the LSD is not rebuildable. The e21 LSD is still rebuildable.
.

Same design pretty well all the way through from what they tell me, you can use e21 parts to rebuild a e36 small case lsd and the the same number of clutches.

reramping and adding extra clutches doesnt seem hard in theory, ive gota get round to pulling my e24 side loader apart and see where we can take some metal away to achieve this. plus i need to see if the mid case e30/36 gear sets fit. Then its time to cut up an unsuspecting rear subframe.

[joey79]

e24 diffs aren't side loaders, and e30/36 188mm gear sets are interchangeable with e24.

Changing lockup isn't accomplished by adding extra clutches, but by using different thickness spacers. "Outer disc" (#8).

http://realoem.com/bmw/showparts.do?...30&hg=33&fg=15

[jrcook320]

e24 diffs aren't side loaders, and e30/36 188mm gear sets are interchangeable with e24.

Changing lockup isn't accomplished by adding extra clutches, but by using different thickness spacers. "Outer disc" (#8).

http://realoem.com/bmw/showparts.do?...30&hg=33&fg=15

I think both will increase lockup. More clutches improves clutch life, as well as offers more friction surface which will increase lockup for a given clamp force.

My wife got me the parts to rebuild my lsd for christmas with the help of a friend, who discretely consulted with me. lol We made sure to get the 2.1mm outter discs and new belleville washers.

[Beemer Tech]

e24 diffs aren't side loaders, and e30/36 188mm gear sets are interchangeable with e24.

Changing lockup isn't accomplished by adding extra clutches, but by using different thickness spacers. "Outer disc" (#8).

http://realoem.com/bmw/showparts.do?...30&hg=33&fg=15

im sorry i find it quite confronting and almost insulting to be told im wrong when i know otherwise.

pre 1982 e24 were based on the e12 and had the side loader diffs (as i mentioned, i have one of these setting in my shed) post 82 were based on the e28 and had the 188mm e28/e30/e36 ect ect ect diffs. The side loader crown wheel is the same diameter, has the same size and number of bolts, but the jury is still out on if they are interchangeable.

in an posi LSD's like ours you have two types of lock up, static (preload) and dynamic (ramp angle), adding one will effect the other. adding extra preload (by adding thicker clutches and or dogs (ions, floaters, spacers as you call them)) makes them lock more but means there is more drag between the wheels, as if the lsd as partially locked all the time and can have negative effects on rear end stability and tends to heat the diff up. while changing (reducing) the ramp angle will add lock on acceleration and deccel, you can even have more lock under acceleration than deccel if you have less angle on the corresponding side of the thrust plate. the idea behind adding extra clutches means the clutches wont have to as much work to create the some amount of friction so they last longer and dont get as hot.

so the ultimate is to add extra clutches, reduce the ramp angle and preload. this means better turn in, increased lock under acceleration and mid corner stability, longer clutch life and a cooler running diff. i know metric mechanic do this with their diffs and like i said in theory it should be pretty easy to achieve with a mill, different thickness dogs and clutches.

[joey79]

Sorry man, I wasn't trying to insult or confront. I had no idea the old e24 diffs were side loaders. Ignorance on my part i suppose. I've only seen the late type.

[Beemer Tech]

thanks for the apology, its ok we are all still learning. i hope what i said about the ramp angles and extra clutches made sense.

[Tom D]

"Can't we all just get along?" Rodney King 1992 durning the height of the L.A. riots.

no harm, no foul. we drive E21s making us part of the "he man womun haters club". did i just date myself?

for you youngsters, here's a link.

[ame]http://www.youtube.com/watch?v=wBIC8JTQMMQ[/ame]

[midlifebmw]

I liked the one where they built that go kart with all the crazy stuff on it. That inspired me and the entire gang back in '77.... no one's lawnmower wheels were safe that summer!

[jrcook320]

in an posi LSD's like ours you have two types of lock up, static (preload) and dynamic (ramp angle), adding one will effect the other. adding extra preload (by adding thicker clutches and or dogs (ions, floaters, spacers as you call them)) makes them lock more but means there is more drag between the wheels, as if the lsd as partially locked all the time and can have negative effects on rear end stability and tends to heat the diff up. while changing (reducing) the ramp angle will add lock on acceleration and deccel, you can even have more lock under acceleration than deccel if you have less angle on the corresponding side of the thrust plate. the idea behind adding extra clutches means the clutches wont have to as much work to create the some amount of friction so they last longer and dont get as hot.

so the ultimate is to add extra clutches, reduce the ramp angle and preload. this means better turn in, increased lock under acceleration and mid corner stability, longer clutch life and a cooler running diff. i know metric mechanic do this with their diffs and like i said in theory it should be pretty easy to achieve with a mill, different thickness dogs and clutches.

makes perfect sense. Thanks for the info. At only .1mm increments, I wouldn't think the difference in static lockup would be that significant from 1.9mm to 2.1mm. I wonder what the stock disc thickness was (like anyone could get an accurate measurement at this point)?

I've heard actually adding a clutch disc requires machine work on the e21 diff. I'll know more once I actually get around to tearing mine apart.