FD and RX-8 Diffs interchangeable?
 

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.

I too would like to know this.

I also wonder if they are any stronger.:dunno:

This thread indicates that 4.77 gears from a Kia Sportage can be put in an FD diff - for < $300.

http://www.hacstl.com/forums/showpos...81&postcount=9

Apparently this is fairly well known in the S2000 Community.

I forsee having two diffs, one with a 4.44 and another with a 4.77 depending on the track and event. Hmm...

I am definitely going to get a 4.44.... but that 4.77 is very tempting for autocross...

Does anyone make a taller 5th gear? Then I could run the 4.77's and still be able to hit the freeway every now and then.

Well had an close look at the RX-8 Diff and it won't work with FD powerplant frame or diff mount. Bummer.

I have read you have to remove the gears and put them in the FD Diff. Hope this helps.

better be just the gears. I just bought a 4.44 ring and pinion to go in for drag racing.

From what I have read I think the internals may be interchangeable.

I had the entire RX-8 Diff - it was pretty obvious that the complete thing would not be a bolt in. That would have been sweet.

Whenever I get around to the swap, I will find out if the diff assembly is interchangeable.

That would be really nice if they are. I've been wanting a diff. set but IMO 4.3 isn't worth the money and 4.77 is just to much. I've always wanted something close to 4.5.

So the 4.44:1 isn't close enough to 4.5:1 for you?

Yes it is that's why it would be nice if it's interchangable.:icon_tup:

Only the RX8 ring and pinion can be used as a replacement in an RX7 diff, you can not use the RX8 differential case or differential.

Hope this helps,
Dan