Wondering about LSD identification...

[BSH]

I'm thinking about trading my stock 3.15 LSD for a 97 auto M3 3.38 LSD.

I was wondering if there are any markings on the differential case that identify it as either a LSD or the specific ring-and-pinion set (3.15, 3.23, 3.38, etc.) inside?

Is there a VIN tag or anything that tells you which car it came from?

Any info is greatly appreciated.

[BSH]

bump.

[E368]

Yep, there should be an aluminum tag on one of the rear case bolts that shows the ratio, e.g. 3.15, 3.23, 3.38, etc. On that tag it should have "S" stamped to indicate LSD. I have also seen a painted marking on the top of the diff case.
All E36 M3s have LSD standard.

[BSH]

Thanks, Rob.

Is the E36 325 3.91 LSD the same as a E36 M3 diff, except for the gearing??

[like2short]

Yes, pretty much the same except for

1. Flanges...no biggie...just swap 'em.

2. M3 uses a bolt with a 14mm shank to secure the ring gear to the internal LSD unit, 325s and most other bmws use a 12mm shank.

3. Also the 3.73 gears from an E30 will fit as well if you want to swap gears.

[BSH]

Swapping gears is just as costly as purchasing a rebuilt diff, isn't it?

All I read about on this forum is that there only a select few tuners who have the tools and ability to rebuild a diff with a different ring/pinion set and lock-up.

If this is true, what is the benefit in 'swapping gears'?