Diff Experts-Please chime in on 2 or 3 clutch

[brads2002]

I am rebuilding a diff for my dedicated track car, a gutted 325i with a M20. For years I have been running an 4.10. The last couple years i have been smoking the inside tire on uphill turns (which were i run has a lot of).

I just removed another 4.10 medium case from my 318 due to an engine swap. I decided I would rebuild this unit and when i pull the track car out of storage toss it in. This 4.10 seemed fairly strong. I pulled it apart (without stripping any of those allens) and it has what looks like a little wear on the clutches. Since i am in there i figure i will replace the wear parts. What is the consensus on running a 2 clutch vs 3? Its really a DE car so i am not looking for every 1/10th of a second. I am more concerned with tearing up my slicks on hills. Also is there any benefit to porsche vs bmw parts?

Thanks for any help. This is new territory....

[TobyB]

The stock (25%?) diff is pretty underwhelming on the track-
if you're in there, I'd upgrade. Others know more than I,
and will chime in.

That said, I have driven cars that were set up such that
they could spin an inside tire with anything less than a spool.
I've also driven well- balanced cars with an open diff that could
put inside traction down well in almost any corner.
Suspension setup plays a big part in this...

t

[brads2002]

Thanks. Good point on the suspension. IE spec springs, IE front camber plates, IE sways, Bilsteins, poly bushings all around, stock 14" wheels.

[Preyupy]

I'm with Toby. Where do you have your rears sway bar set? Try softening it up and see what happens.

[brads2002]

I guess what had me thinking the diff was the main contributor is the sway bar has not been adjusted but the wheel spin has gotten worse. I will play around with the bar and see how that helps.
Either way I plan on rebuilding this sucker with new disks and plates. I figure since I am in there an its 30 years old. What are the thoughts on 2 vs. 3 clutch?

[Wanganstyle]

Diff Experts-Please chime in on 2 or 3 clutch

I guess what had me thinking the diff was the main contributor is the sway bar has not been adjusted but the wheel spin has gotten worse. I will play around with the bar and see how that helps.
Either way I plan on rebuilding this sucker with new disks and plates. I figure since I am in there an its 30 years old. What are the thoughts on 2 vs. 3 clutch?

4 plates with no preload and proper stack setup is the proven optimal setup for these ancient zf Diffs.

Nasa national championship spec = you get results with.

If increasing plates more than Oem 2 without removing preload you are increasing static breakaway which = understeer for low speed corners.

If you like understeer go for it; free internet data from those selling cheap knock off parts is just that.