Well, I've managed to invest the better part of my day today reading and researching BMW diffs and LSDs. Here's what I've been able to gather with reasonable certainty:
Early 168/188/210,215
Used on early BMWs to late 90s (98/99?), and continued on M cars through all E-chassis
-identified by having the bolt-on side covers
*Does not share parts with "K" or "L" series diffs below
Model 168K/L
Axle seal bore measures 78mm
*168K*
4 cyl cars up to 2006
uses taper roller bearings
E46
Z3?
*168L*
4cyl cars from 2006
uses ball bearings
E8X, E9X, F-?
ie: 118i, 120i, 318i, 320i etc
Model 188K/L
Axle seal bore measures 90mm
*188K*
6 cyl cars up to 2006
uses taper roller bearings
E46
Z3?
5-series?
*188L*
6cyl N/A cars from 2006
uses ball bearings
E8x, E9x
ie: 128i, 130i, 328i, 330i
*early 135i automatic models
Model 215L
Axle seal bore measures 100mm
6cyl turbo cars from 2006
M cars from
E8x, E9x
ie: 135i manual and 135i DCT
**K/L interchange notes:
-Ring & Pinions are not interchangeable between K/L series
-Bearings are not interchangeable between K/L series
-LSD units ARE interchangeable between K/L series
Sources:
http://www.limitedslip.de/bmw/hagtypen.html
https://www.difflab.com.au/collectio...5lw-late-large
https://www.kmpdrivetrain.com/produc...ials/bearings/