3.64 differential swap in pre-LCI 3.0 5MT

[e39_touring]

I was getting ready to order parts to do an oil pan gasket job and swap in these 3.64 front & rear diffs that I've had for a while, but I'm running into something that changes my understanding about the differential swaps that I've seen in other threads.

Does anyone have a pre-LCI differential (actually, the stub axles) from a manual trans car lying about to take a few measurements?

Here's what I (thought I) know going into the swap:

1) front differentials are drop-in, plug and play - no differences there
2) rear diff stub axles have a 94mm bolt circle on the manual vs. 86mm for the auto/4.4 cars so axles are not interchangeable
3) both the pre-LCI manual and all 4.4L cars share the same rear differential case
4) post-LCI manual cars have the large differential case

Now looking at realoem, I see that the axle seal and snap ring are different sizes for pre-LCI manual vs auto/4.4L cars (#13 in this diagram https://www.realoem.com/bmw/enUS/sho...diagId=33_1013)

I was always under the impression that on the small-case differentials the diameter and splines of the stub axles were the same (i.e. you could swap differentials if you use your old stub axles). But, this looks to not be the case. I would have to swap to the smaller stubs and axles of the automatic cars if I were to perform this swap. I know a few of you have done this, and I hope you can clarify for me!

[e39_touring]

Point of clarification - from # 2 in this post:

https://xoutpost.com/1024694-post10.html

"2) The manual flanges will go right into the auto diff, and my car now has one of each in it, since I had an episode with one of the new auto CV bearings puking its cage and ball bearings all over the garage floor. I got one from ECS that was supposed to be VIN matched to my car, which was really huge (length and splined diameter) and did not fit either differential."

From my research in realoem, this shouldn't be possible, but it's exactly what I was hoping to do - put manual flanges (stub axles) in the auto differential.

[e39_touring]

I have confirmed that the rear differentials are interchangeable if you pop out the stub axles and swap those over, too. I can't post pictures from my android tablet but will do so later if I remember when I'm next on my PC.

Basically, all the pre-LCI do share the same differential case and internals (except ratio). The bolt flange on the side axles for the MT, is, and 4.4 with high-speed synchronization (I think this means lack of speed limiter) models is a touch larger than the other cars. The splines and shafts on the stub axles are plug & play swappable.

Those same cars but in LCI years went to a larger rear differential case that have larger side axle assemblies that are not interchangeable. You can still use the differential in any car, but you would have to change out your full axles (not the stubs) as well to match.

[e39_touring]

Here's a picture showing the difference in rear stub axles. The one on the left is from a 4.4L, and the one on the right is from an '01 3.0 5 speed.

On pre-LCI, this means 3.64, 3.91, or 4.10 ratios are very easily swappable. On LCI SAV's, you still have those same choices in ratios, but MT or 4.8is SAV's will may have to change out the rear axles depending on what diffs are sourced for the swap in ratios.

[Jps1995m3]

Originally Posted by e39_touring

Here's a picture showing the difference in rear stub axles. The one on the left is from a 4.4L, and the one on the right is from an '01 3.0 5 speed.

On pre-LCI, this means 3.64, 3.91, or 4.10 ratios are very easily swappable. On LCI SAV's, you still have those same choices in ratios, but MT or 4.8is SAV's will may have to change out the rear axles depending on what diffs are sourced for the swap in ratios.

Have you installed the front and rear differentials on your car?
So you’re saying with the rear differentials for the flanges you have to install the axles for the swap and you can’t just change the flanges from the 3.0 manual to the 4.4 ,3.64 diff?

[e39_touring]

Originally Posted by Jps1995m3

Have you installed the front and rear differentials on your car?
So you’re saying with the rear differentials for the flanges you have to install the axles for the swap and you can’t just change the flanges from the 3.0 manual to the 4.4 ,3.64 diff?

They're installed, but I'm still piecing together the rest of the truck after tackling a bunch of other stuff underneath.

If you go back to post #4 above, I attached pictures of what I call 'stub axles'. These pop in and out of the rear differential, and what I call 'full axles' or 'axle shafts' bolt onto the stub axles on one end and the wheel hub on the other.

Changing from a pre-LCI (5 speed) manual stock (4.10) diff to a 4.4L (3.64 ratio) diff requires moving your manual stub axles to the new 3.64 diff (and then reusing your manual axle shafts with it). I did it this way since you have to pop out the stub axles anyway to replace the differential seals, and any future axle replacements will match the way the truck was originally configured. The alternative is you can use the stub axles that came with the 3.64 differential, BUT you have to use the matching axle shafts that came with the 4.4 X5 as the ones from your manual won't bolt up (again, see the pic in post #4). The wheel end of all the E53's is the same.