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Old 05-04-2012, 11:29 AM   #79
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Join Date: Jan 2008
Location: Northern California; SF BAY
Posts: 263
My Ride: e36 M3 / E30 GTS1
Originally Posted by Hornung418 View Post
Since this is an active thread with some knowledgeable people posting in it, I'm curious as to how much lock-up you can modify to a stock M3 LSD. I've found 210mm 3.15 R+P for e39 M5s on eBay for $125, and it's a direct swap to the M3 case. But the OEM lock-up is pretty tame at 25%. So is it possible to add some extra clutch plates with out having to modify the shims?

the E46M LSD unit is a M-variable LSD. this is a Viscous AND clutch LSD, the Viscous coupler engages the multi clutch pack stack. GKN makes this unit, it is NON-servicable.

the e36/30 M cars use a conventional Clutch LSD with 2 disc pairs. They can be and are commonly modified for more discs and more lockup.

Originally Posted by Hornung418 View Post
For the e36 it can either be a 168mm (small casing), a 188mm (medium casing) or a 210mm (large casing) ring diameter, the e46 LSD has a 210mm ring diameter.

I think I'm going to hold out and get the M3 rear and swap the 210mm 3.15;1 R+P.

Edit: Is "Mr. Wizard" Wanganstyle?

Nope. No wizard or magic here!

Just a lot of diff building for my own cars over the last decade. I started in Rally cars (AWD) - lots of LSD setup there.

I have built up with my own hands here in northern california:

e46M diff with 3.15 and 3.23 and 3.73 and 3.91. Using all OEM bmw parts; all 210mm and no wizardry needed. Fit is = BMW OEM designed fit.
e46 non-M diff with custom ratio and OS-Giken LSD (aftermarket). Fit = almost as good as BMW OEM fit (but case grinding is required to fit the OSG)

BMW OEM 210mm and 188mm gearsets have different mounting hardware standards. Some use M14 hardware/holes/threads and some use M12. Not easily mix and matched, not cheap to play with either. Everything is hardened, surface treated. Don't assume you can drill/tap anything.

the 188mm e30/36 ring and pinion with high locking setup has been proven to take over 1krwhp by a bay area local I setup. They are very strong if setup correctly. 210mm is for durability, long term wear.

e39/46 use compact nose pinion gears; not compatible with older cars.

I have played with the 188mm compact e39/e46 diff shell and decided it was not worth my time to stuff in an older e30 lsd unit - it doesn't really fit. I have both e46 non-m housings and e30 LSD units of various flavours here.... I have tried yes.

I have built OSG+ 330i e46 units for race cars in custom ratios, that was worth my time (and the customers time). Even installing the E46 non-m special OSG LSD into the Non-M case was a PITA and required grinding the case.

Last edited by wanganstyle; 05-04-2012 at 12:12 PM.
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