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LSD Half Shafts - an Idiot's Guide

Giving a nod to the 70’s Volkswagen repair manual that spawned countless others, my post is a distillation of several other posts on how to construct half shafts that work with the installation of an e21 LSD in your ’02.  In all cases, the e21 parts referenced are the “later” e21 parts. In my case, I believe that they came from a 1980 320is.  Other posts and reference material cite differences in dimensions of “early” half shafts, CV joint bolts and differential widths. See the end of this article.

 

Primary problem:  stock 2002 half shafts (CVs plus axle) are too short with a e21 LSD installed. Why:  the LSD is ~10mm narrower.

 

Secondary problem: the inner 2002 CV won’t bolt to the later LSD. Why: because the LSD uses 10mm bolts and the 2002 CV uses 8 mm bolts.

 

Solution: Use later e21 half shafts, replacing the outer e21 CV with a 2002 CV. This allows the inner CV to bolt directly to the LSD output shafts and the outer CV to bolt directly to the wheel input shaft. The 2002 CV is used without the cupped washer that comes on the stock half shaft.  The inner CV has a ¼” (6.5mm) spacer between it and the LSD output shaft.  That’s it.

 

Of course, you should take everything apart, clean and inspect the CVs and re-grease them. New CV boots and clamps finish off the project.  The taking apart can be facilitated if you have a hydraulic press. A couple of the CVs nearly fell off with a light tapping, but a couple needed persuasion.  I found a friend with a press which reduced the stress on the axle shaft ends that results from banging on it. Just make sure the circlips are removed first.

 

Details

I took a number of measurements of the e21 and 2002 parts. I also took some photos. 

What I learned was that the stock 2002 half shaft and the hybrid shaft described above are exactly the same length (see photo),

IMG_0299.thumb.JPG.56224480863d22abfc3fc3a49bf7156c.JPG

 

yet the e21 LSD is 10mm narrower than the stock 2002 differential. This can be seen in the photo of the two differentials sitting side by side with a level on top to the 2002 output shaft.  It’s sitting on a shoulder that is ~1mm-~2mm higher than the mounting surface, but you get the idea. 

IMG_0319.thumb.JPG.1cf6a90d28df5ef437a0c6abce235c9b.JPG

 

The spacer mentioned above closes this gap.  I had spacers that were 6.5mm each (1/4”), so I used them. I would have preferred to use 3/16” or 5mm, but I couldn’t find any, so I went with what I had. The ¼” variety are readily available from all of the well know ’02 suppliers.

IMG_0324.thumb.JPG.284f6fae63386a84a4eea270f13273fb.JPG

 

More details

The cages and balls in the e21 and 2002 CV were identical. The axle shafts were not.  The 2002 shafts were shorter end to end (top shaft in photo), but interestingly also had longer splined ends which I surmise is why they used the cupped washers to take up the space required to secure the CV with the circlip on the end of the half shaft.  If you try to use the cupped washer on the shorter splined 320i axle, there is no way to install the circlip. I tried.

IMG_0321.thumb.JPG.c95e40656c4c5f022d7136f8708b0479.JPG

 

Extraneous stuff

I wanted to use Oetiker clamps on the dust boots which came with a prior rebuild kit. These are single use items, but low profile and very secure.  I couldn’t find them at any of the local auto parts shops, so I ordered them from a metric parts house: Belmetric.com.  Part # 16300029 on the CV end of the dust boot and # 16700042 on the axle end of the dust boot. These require special pliers to install and given that the local auto parts store no longer carried the clamps, they also no longer loaned out the pliers required to install them.  Instead, I borrowed a pair of my friend’s pricey Pex clamp pliers which worked perfectly.  The $12 Home Depot variety didn’t work (well).

 

I also ordered conical lock nuts for the 8mm outer 2002 CV bolts.  They’re called stover nuts and have oblong looking holes.  These are lower profile than conventional nylock nuts and are what were used on the stock 2002 drive shaft flanges. They are <1/2 the price of the BMW versions.  

Bel-Metric’s parts were shipped express, so I had them in 2 days. Pretty good service and the parts were just as expected.

 

The back story

I started all of this because I wanted to fix a leaking LSD rear cover.  When I originally did this conversion 10 years ago, I used a conventional gasket which always leaked, so I decided to use Permatex Ultra Black on the do over.  While preparing to remove the LSD, with the car on jack stands, I noticed that the differential output shaft on one side was pulled out of the differential by 1/2”. There was a huge gap between the output shaft dust cover and the differential which kind of freaked me out.  This only seemed to occur when the wheels were up in the air and their weight pulled the output shafts part way out the differential.  The same thing might happen if an energetic driver got the car airborne, which it turned out my son had.  It explained the splatter of Redline dripping off the differential onto my garage floor.

 

What was most amazing about this was the discovery that when I originally did the LSD install and the half shaft conversion, I used the 2002 half shafts, which from the photos above, are much shorter.  And yet the car ran around for 10,000 miles without any (obviously) adverse effects.

Is there a lesson here?  Just do it whatever and it will probably work? Maybe, but the great news with this site is that after I did the conversion the first time, a lot more intelligent questions were asked, with knowledgeable answers given, which helped me to get this done right the second time around.

So, thanks to the FAQers who preceded me in answering questions and documenting their projects. I’m happy to add my story to the list.

 

Parts List

Quantity              Description

  1                       2002 half shaft – only need the 2 CV joints, save cupped washers for another project

  2                       e21 half shafts – need 2 axles and 2 CV joints from later year

  2                       3/16” or ¼” spacers

12                       10mm x 65mm  Allen head bolts

  2                       Half shaft rebuild kits (2 dust boots, 2 large and 2 small Oetiker clamps, 1 tubes grease)

 

Good references, with more detail,  are :

 

Ireland Engineering Differentials article: http://www.bmw2002.com/documents/bmw-2002-differentials.pdf

2002

 

FAQ post (see “Gil by the way of Gary” text):

 

2002 FAQ post, e21 Diff Install with 320i Inner CV Joints:

 

2002 FAQ Post, How to Replace a Differential:

 

 

                                               

 

 

 

 

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