I want to try either an RX8 6speed or an FC turbo 2 5spd on my NA 13BPP motor for road racing (tube chassis 7s Only Mazda GT car). Anyone seen it done. Any tips or tricks.

The car currently has a T2 bell housing and adapter plate to run a jerico 4speed.

 

IIRC, you need T2 flywheel, clutch and starter. and a automatic transmission driveshaft.

 

the Rx8 trans will bolt right up to the engine, it uses a T2 size clutch/flyywheel. the starter has a different ear on it, so its unique, but it is otherwise the same as a T2/FD. the later Rx8's got an upgraded 2kw starter, 06 and up.

the shifter is a couple inches further forward than the FC transmissions. it also has a PPF mounting, but it would be pretty simple to make a mount, Mazda gives you giant studs.

it takes a turbo size driveshaft, i think the length is the same too, but don't hold me to it.

the ratios in the Rx8 box are 10,000,000 times better than the previous transmissions for an NA, they are basically the competition gear set with a granny 1st

the shafts and stuff are really beefy, but the shifter stuff (hubs,forks etc) aren't great. the 09+ transmission is considered better but its not much better, the 09 transmission is shared with the NC miata, and the ford rangers... the 04-08 is an Asin Warner, and its relatives with the NB miata, S2000, 350z, is 300.

 

I have an 04 in my rx3. I run a large street port 13b and a 4.44 rear. It works great so far

 

Why are you ditching the jerico?

I road race an FC (NASA ST3) and have a RX8 s2 trans in my FC and my buddy has a Jerico dog box in his FB. I used an ebay shift lever extender to get a few of those inches back you will lose compared to a FC T2 trans. IMO don't bother with the T2 trans. The RX8 has better ratios and shifts way way way faster. I run a 4.10 rear end.

Compared to the Jerico it shifts slower, but for ST3 my initial impression is that its not worth the points modifier that the dog-box.

J9, I had have my turbo drive shaft cut down a bit to get it to fit, don't recall how much though.

A couple other notes, the miata shift tower and shifter are different, the miata is slightly shorter throw and can be adapted to work on the RX8 box. The shifters themselves are basically identical except that the distance from the pivot to the ball is different, and a matching change on the miata shifter tower to make it work. It saves...maybe 2-3% in throw and is 'oem' quality. You could also buy the $99 NC miata short throw and cut down the spacer to get it to work, though I have not done this to verify quite yet.

 

i've had the miata and Rx8 boxes apart, and its really weird how they are the same transmission, but really don't share any parts. that being said the NC transmission is a P type, so its a different family/design

 

Interesting. I assumed that the reason for the subtle changes to the tower was more to do with 'poke yoke' so that they don't manufacture with wrong parts by accident. The shift tower won't interchange without spinning it around and moving some pins.

I hadn't looked deeper into the box to realise that they are that far off. I guess that makes a bit of sense as to why my NC trans feels fairly different then the RX8 box.

 

the NC transmission is a 6 speed version of the Ford truck transmission, the S1 Rx8 transmission is made by Asin Warner

 

Ah, Good call I never specified. I put in an S2 box, not an S1. If I recall the S2 box and the Miata box are very similar.

 

yep they are basically the same, its a 6 speed version of the transmission Mazda sold Ford in the 90's.

https://en.wikipedia.org/wiki/Mazda_M5OD_transmission