I've seen several mentions of plans to use the 320i inner cv joints when installing a limited slip diff from a 320is but didn't find any posts about how it went. Most were aiming to avoid both using spacers and redrilling the diff output flanges. I was only concerned about avoiding the latter. I decided to take a few photos along the way to document what I found. There are lots of articles about other aspects of the swap so I'm just focusing on the dimensions of the axles below to supplement what's already out there.
Redrilled output shafts would be a much easier approach with minimal downtime if your 02 CV joints are still good. I wasn't so lucky.
I knew I had one bad '02 CV joint and the other three had dry, cracked boots so I'm repacking four cv joints regardless.I purchased the 320 halfshaft assemblies with the differential. The 320i joints looked pretty good, without any tears in the boots but they were cracked and due for replacement as well. I figured I could salvage two good 320i joints, and at least two of my '02 joints should be good.
Lots of posts I read on the topic were asking if this approach would allow installation without spacers. I didn't find any posts confirming it would work so I ordered a pair of IE spacers drilled to 10mm for the 320 cv bolts, and a longer set of bolts just in case.
Donor 320is for the axles and diff was an 83. My 02 is a 74. Earlier years of 320i used thicker CV joints that would require a different solution;
33 21 1 205 746 ..... 2002 & 320i >08/1978 (M8 bolts)
33 21 1 207 277 ..... 320i 09/1978>09/1979 (identical to above except M10 bolts)
33 21 1 208 439 ..... 320i 09/1979> (narrow width & M10 bolts)
1976 2002s are unique as well. You'll apparently have it easier than most by just swapping your 2002 diff flanges into the e21 diff.
Here are the axles side by side. All my photos are before or during disassembly and cleanup so please don't give me a hard time about how dirty everything is. :-)
The 2002 axle is on top, the 320i on the bottom. CV joints are fully compressed for consistency. As you can see, the 320i halfshafts are quite a bit shorter overall than the 2002's. The CV joints themselves are quite a bit thinner, too. I started to question whether this was going to work but I decided to press on and see what the axles look like.
Here are the bare axles;
The 320i axle is on the right. Quite a bit longer than the 2002 axle on the left. There's still hope!
Next, I test fit a 320i cv on one end, and an 02 cv on the other end of a 320i axle. My other '02 halfshaft is shown here for reference. Again, both are fully compressed.
They're the same length! Since the 320i differential is narrower than the '02 diff, this means I'll probably use the spacers.
I checked fitment on the car and while the CV flanges could reach the diff and stub axle flanges without the spacer, the spacer moved the cv joints closer to the center of their range of extension both at parallel to the ground (shortest flange to flange distance), and at full droop (greatest flange to flange distance).
10/15/15- Checking back after ~1 year and a few thousand miles. Everything is still working great.