After wanting to try a true clutch-type diff for years I've finally ordered one! Planning to self-install and figure I would chronicle the process to help others thinking to do the same. Bare with me as this is going to be a slow process and will likely take weeks for me to complete. Also, not really intending this as a DIY but more of a good source of info. My car is on jackstands already waiting on a new custom suspension setup (more on that later), so figure I may as well do this now while the car is not in use.
I went back and forth on which diff to get and ended up deciding on an OS Giken Spec-S. While I could have gone Spec-X or customized my Spec-S (effectively making it a Spec-X), I decided I'd start with Spec-S and then customize it later if I decide to do that. I'm also sticking with 3.15 gearing for now (DCT transmission) to make the install easier and also maintain street manners. Again here, I may end up swapping the gearing at a later date as my car becomes more of a dedicated track car, we'll see.
Some informative YouTube videos on OS Giken diffs:
MotoIQ on OS Giken Function and Tuning
OS Giken Superlock Spec-S vs TCD Spec-S
Some informative YouTube videos on installing diffs:
Driftworks installing a Florian Diff
RacingDiffs - How to Change a BMW Gear Ratio
RacingDiffs - E46 M3 Complete Differential Rebuild
E36 M3 Diff Rebuild
E46 M3 Differential Oil Leak Fix
While these videos don't cover our exact diffs a lot of the same concepts apply.
I'm also assembling a parts-list and could use some help filling in a few blanks.
Parts List:
2 x E39 M5 Output flanges - part no. 33131214068
2 x E92 M3 Shaft Seal w/ lock ring - part no. 33107510289
Note: This is the seal for the output flanges, be careful not to confuse with the pinion shaft seal
2 x E92 M3 O-rings - part no. 33111214144
2 x E92 M3 Differential Carrier Bearings -
2 x E92 M3 Differential Carrier Bearing Races -
Diff cover sealant -
Sealant for side cover bolts that protrude into diff housing -
OS Giken Differential Fluid - Need 3 Liters, ~1.2L/fill but need to flush and refill after ~500 miles
Reason to just stick with Giken fluid vs. substituting -
LINK
Some additional useful links:
E92 M3 Differential Parts Diagram
E39 M5 Differential Parts Diagram