The Rx8 6-Speed into an FB Thread!
 

Im sure much of the information can cross into other chassis.

General Rx8 Transmission Information

Mazda Rx-8 04-current 13B Renesis Gearbox (manual)
1st: 3.815
2nd: 2.260
3rd: 1.536
4th: 1.177
5th: 1.00
6th: 0.787

The most popular "close ratio" conversion i have seen is the miata box. Below is a comparison of the miata box to the Rx8 box given a 9000 shift point and 4.78 final drive (my personal setup).

http://img.photobucket.com/albums/v2...rx8vsmiata.jpg


Now here is the 12a transmission i have currently versus the Rx8. much better!

http://img.photobucket.com/albums/v2...Q/rx8vs12a.jpg


And also the Turbo II's R type transmission (87-88) compared to the Rx8. Again, 1st and 2nd are similar, but from there on out, for my natural aspiration application, the gearing is superior.

http://img.photobucket.com/albums/v2...8vsTurboII.jpg

Parts Needed For Swap and Other Considerations

-Mazda Rx8 Transmission. 04-08 (not familiar with the newer 09 up models as they are a different manufacture but im assuming this same guide line could work)
-Turbo Flywheel and Clutch (compare 235/240 to the 236 of the Rx8)
-Rx8 Starter
-Rx8 Shifter
-Metal stock for the transmission mount
-Solution for the slave cylinder, will finalize something soon enough
-Final solution for drive shaft will come soon. Output shaft is same as a turbo II though.

Things to Think About

Now my setup lends this swap to be simpler than most. The transmissions in the FB were shorter than the FC chassis so the shifter position is not as effected as the FC will be. For the FC the shifter will move 3.5" forward. This will be less for the FB. Guesstimating around 2" to 2.5" for the FB. Add that to the fact im tall and the shifter location is essentially a non issue.

Also, i dont have a speedometer so the whole electronic speedo thing is a non issue for me. If you happen to want to retain the mechanical speedo, then well, you have problems that im not going to address for you. Real men don't need speedos. Or wear them. Its a man law.

:rofl: Lemme know if you need any measurements, diameter, splines, etc etc etc.... I have that box dissasembled on my work bench right now.

i wouldnt mind an any and all if you can. Also note my pm.

in particular, the input and out splines and diameters, length of the transmission, pictures of mount location etc.

Subscribed! I am very interested in your results.

minor update, i have sourced myself two transmissions, maybe three. Moving at the end of this month so i wont be messing around with that for a little while still. But once i have them on hand ill be taking them apart.

I'll be doing this soon in my FB with a NA 20B powering it. Gonna move the whole engine back to get the shifter to line up and help with the weight balance a bit.

I am considering this behind a 13bt in my 83 but i see the results are for a n/a app.

Any updates?

I thought the RX-8 trans was not that strong. weaker then the TII

He's deployed right now.

I've heard it is too, but I'm not sure if this is going to be a boosted application, so it might not matter.