Repurposing OEM BMW LSD Core into 128I Diff Housing

[Bambambambee]

Hi,

128I 6MT owner here.

I'm planning to swap out my 3.23 diff for a 3.73 one, and initially planned to go with a custom unit. I talked to a few builders (PG, Florian , etc) but life took a crazy turn and going that route is no longer an option. I'm going to be taking an automotive course on drivetrain, and rebuilding a diff is a part of the curriculum. I figured that this would be the perfect opportunity to build a clutch-type LSD, since I'll have access to a full shop (and experts in the field to guide).

My question is - does anyone know if there are any OEM BMW clutch-type LSD cores that can be repurposed into the 188L housing? My understanding that any LSD core from a 188mm size should technically be able to fit (with some minor clearancing/machining), correct?

My initial research tells me that the M Performance LSD core (Drexler units) for F3X will fit, but it looks like these are discontinued. Looking for cheaper alternatives if they are available.

I also understand that ramp angles from OEM LSDs may not be ideal - if I were to machine the ramp angles, I can probably only safely take away material, so achieving the desired angles may not be possible. This is fine as the goal of this project is to be a learning experience and my 1'er is a street car anyways.

I know this is a long shot, but if anyone has experience here, would love to pick your brain!

Thanks

[spidertri]

So you'd probably want the 188 size LSD unit from an E30 or E36. I've seen threads where people have been able to fit those diffs into the non-M E46 188 housing, so something similar may be possible for the E82 diff housing.

I think the biggest change from the 188L E46 housing to our 188LW housings was the change from tapered roller to ball bearings on the output flanges. But there could be many more changes.

https://www.e90post.com/forums/showthread.php?t=1472442

You'd probably want to get both units on hand and start taking some measurements to make sure the ring gear flange was in the same location, # of ring gear bolts and their size, would new stock output bearing work or would you need to find a different size? Will the axle stub shafts have the same number of splines or do you need to use the stub shafts from the donor?

As for the ramp angles, typically diff builders can cut at least two sets of ramps into the pressure plates, you just machine the new ramps at 90* to the originals, then as you build it just make sure you select the ramps you want to use.

Cool project, would love to see more about it. If you used an E36 core you can machine it to accept 4 clutches, stock was only 2 clutch plates.

[MOD.Works]

ZF006 unit

[Bambambambee]

Originally Posted by spidertri

So you'd probably want the 188 size LSD unit from an E30 or E36. I've seen threads where people have been able to fit those diffs into the non-M E46 188 housing, so something similar may be possible for the E82 diff housing.

I think the biggest change from the 188L E46 housing to our 188LW housings was the change from tapered roller to ball bearings on the output flanges. But there could be many more changes.

https://www.e90post.com/forums/showthread.php?t=1472442

You'd probably want to get both units on hand and start taking some measurements to make sure the ring gear flange was in the same location, # of ring gear bolts and their size, would new stock output bearing work or would you need to find a different size? Will the axle stub shafts have the same number of splines or do you need to use the stub shafts from the donor?

As for the ramp angles, typically diff builders can cut at least two sets of ramps into the pressure plates, you just machine the new ramps at 90* to the originals, then as you build it just make sure you select the ramps you want to use.

Cool project, would love to see more about it. If you used an E36 core you can machine it to accept 4 clutches, stock was only 2 clutch plates.

Super helpful response! I can't seem to find enough information on the interchangeability between the different generations of the 188 units, so you're right, I'll have to start with comparing the 2 units and documenting the differences. The junkyard/part out e30/36 LSD assemblies are pretty pricey from what I'm seeing ($700-800). Is that really the going rate these days?


Also, is it safe to assume the ZF006 is code name for the LSD core/carrier from the e30/e36?