There's a thread at the other forum discussing interchangeability of RX-8 and FD differential parts.
http://www.rx7club.com/showthread.php?t=797818
It is known that the 4.44 ring and pinion gears from an RX-8 manual diff will bolt up into a FD diff.
That seems a nice compromise compared to the 4.77 gears that many autoxers use. While I autox my car, I also do track days, so the 4.44 would get me out of the corners faster in 2nd gear at autox speeds, but still be tall enough for track use.
So, I bought a low mileage 2005 RX-8 Manual diff with the 4.44 gear set.
The question that remains unanswered is this: Does an RX-8 diff bolt right up to an FD? There are indications in the other thread that this might be true, but no solid answers yet.
If so, that would sure simplify getting the 4.44 gears in my FD.
Anyone here know?
I was going to look on the rx8club.com forum as well, but it is currently down.