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E21 LSD internal info help needed

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I am rebuilding my LSD unit (E21?) that came from a parts car.  Someone has already removed the spacer and added in a third clutch/plate to the assembly.  The problem is that the splines on the side gear (as they come through the compression ring) are undercut too far when assembled, and the first clutch disc gets chewed away by splines that are only very lightly engaged.  See Photos.


I am not sure if someone swapped parts between diff types or what but something has gone wrong here.  I have rebuilt E30/36 diffs so I am fairly familiar with these units but I am not sure about the older stuff so I was hoping someone could chime in.







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What exactly is your question?  You've nailed down the issue.  As you note, it cannot be fixed by simply swapping out to a new disk.


Tell me the output-bearing to output-bearing dimension and I can tell you if you are dealing with an e21 lsd pumpkin or an e30/e36 318 lsd pumpkin.

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My question is how do I correct this, and what exactly has gone wrong? It does not appear that the compression ring is just very heavily worn based off of photos I have seen online. 


I am aware that people swap guts around and i wonder if they assembled an improper combination. 


The inner race of the output bearing bought for a standard 2002 measures 41mm as does the output landing on the carrier. The out race for the 02 measures 72mm as does the cap for the body. 


My goal is to either repair or replace what is incorrect in this unit or but hopefully just parts and not an entire diff


Let me kbow what you think about those numbers and if you would like anything else measured. 


While i have you on the line- do you think I'll be okay taking out the bolts on the 245 getrag to have them replated? I am referring to the M8x125 or so that keep the casing together. I am hoping it won't disrupt the seals, etc. I have one last batch going for yellow zinc and they would look great fresh. 


Thank you very much!



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I think what Andrew's saying is that the fix is to put the spacer back in and go back to 2 discs.

There just isn't enough spline there to support a 3rd disc.

As to whether there is a 'more splined' side hub/socket-  I haven't seen one, but I only run these things on mild street cars...

...racing diffs, I just weld.  Bekuz race kar.  And cheep bastid.



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When I look at the BOM for these parts it does not show a spacer in between these parts. The spacer going back in place won't have an effect on the interaction between the side gear and the compression ring I don't think. Also, it happens on both sides which supports that theory. 


That is is why I am thinking someone has maybe swapped some parts between diff types. 


Thanks for the input!

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On 4/3/2017 at 6:26 PM, Bavarianhoarder said:

Someone has already removed the spacer and added in a third clutch/plate to the assembly.


1 hour ago, Bavarianhoarder said:

When I look at the BOM for these parts it does not show a spacer in between these parts.


^^This is a tad confusing and contradictory.


Can you take a shot of the pumpkin guts in-order-as-removed-from-the-case so we can see what you are dealing with? 


When I was asking for length, I simply meant end-to-end length of the pumpkin so we can start to get a baseline.  The standard 02 open pumpkin, E21 open pumpkin, and e30/e36 318 LSD pumpkins will measure roughly 5.7".  While the E21 LSD measures a bit shorter at 5.05" (and has longer side-caps to compensate).



Edited by AceAndrew
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Sorry for the confusion.  I meant there does not appear to be a spacer in between the compression ring and the side gear according to the Bill Of Materials on realoem etc.  


Thanks to your photo and info I can confirm that the case is an E21 LSD.


I recreated everything tonight from my photos to show how it came apart.  As I said before, it is clear someone has been in here based on the addition of clutches alone, nevermind how they went about it.





As you can see, there are two clutch discs and two floaters on the cap side with the friction disc up against the compression ring.  This is the clutch disc that was too far deep onto the splined side gear and had the splines wiped out as seen in intro.  The body side of the pumpkin was arranged with only one clutch disc but with two floaters.  The floater being up against the compression ring took up the thickness to keep the adjoining clutch disc fully engaged into the splines.  From my experience with newer differentials, the clutch discs went right up against the compression rings.  It seems sensible to have a floater there as a wear item to protect the pricey parts but I dont think that is right either based off the exploded diagrams seen on realoem etc.


I have looked at your extensive diff thread where you build up the ti case (which is excellent, thank you!) and when I see your compression rings and side gears stacked up without any discs, etc I notice that your spline are not sticking out, where mine are.  Looking at the exploded diagrams again, I see part number 8, the threaded washers which I dont think I have unless they are integral with something else.  I feel like my problem comes with center and works it way out since the spider gears seem to dictate the components I am having issues with.


I also measured the stack height of everything onto the cap and it was a conveniently round 3.25", as was the cavity in the body including the smaller shim.  It seems whoever did this matched the stack properly but with things in the wrong order or perhaps those threaded washers.


Thank you very much for the help, always appreciated!




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