Just looking to see does anyone know anything about Rx8 transmission. Will it fit on a FD and what I will need to get it done.
your help will be greatly appreciated. Thanks.

 

I would love to add one to my Fd but everyone I speak to says the rx8 transmission will not be able to handle the rx7 torque.

 

AFAIK it's a Miata transmission essentially, and while it might bolt up won't hold the power.

 

2004-2008 S1 Aisin trans is similar to the NB Miata 6 spd, 2009-2011 S2 Mazda trans is similar to the NC Miata 6-spd

the gearing is different from Miatas and also between the two RX8 versions, Miata PPF mount is on opposite side of tailhousing than the RX8, not sure how the Miata shifter positions compare to the RX8 since the tailhousings aren’t compatible. But it’s located ~3” shorter than the FD shifter position (RX8 engine position shifted further back into firewall)

They are weak compared to the FD 5-spd, the S2 version seems to be more durable, but super low 1st gear

imo you need a stronger trans if you want a 6-speed. I have at least 6 broken ones behind a 270 bhp NA Renesis engine and it really doesn’t fit wrt shifter though that might be modified to work. Unlikely that the ppf matches up either.

So overall not a good idea imo.

.

 

The 5 speed 8's are identical internally to the late FD boxes and the tail housings and bell housings swap over to give you a cheap FD box.

 

its also worth pointing out that the top gear in the 6 speed is shorter than the 5 speeds, so cruising rpm on the freeway goes up. you do get better spacing on the rest of the gears, there is one for every corner

 

Yep, this has been addressed in the past.

The RX-8 6-speed can't handle the power. Also the gearing is crap on an RX-8 - my bone stock RX-8 does 4000 RPM on the highway. I think they tried to gear it to compensate for lack of low-end power.

The RX-8 *5* speed that was in Japanese cars only is the same as the FD's trans. Just swap bell housing and tail shaft over. It's actually upgraded a bit as well. But it can be hard to find.

Dale

 

Ah did you get a different box in the US for the 5 speeds? In the UK the domestic 5 speed boxes work. They even have the area of the output shaft to attach the speed sensor even though the 8 doesn't use it, pretty cool. They are super cheap here!

 

in the US we basically only got the High Power car, for 2004-2005 we got the low power but its automatic only. or if you like we only got the 6 speed here

we also didn't get the automatic climate control at all, until 2009 (it is possible to retrofit it)

 

The Rx8 transmission is really only a viable option for high HP non-turbo cars, as it's designed for higher RPM ranges and low torque. Heck, RE Amemiya threw an Rx8 six speed in one of their track built FD's that was sporting a non-turbo peripheral port engine.

If you're turbocharged, I could see the Rx8 transmission disintegrating under the torque.

 

The series I (04-08) RX8 6 speed manual is basically made of glass. The series 2 6 speed is better, but still unsure how much torque it can take...for what its worth I think they also used that on the Fiata 124 Spyder/Abarth so maybe it can take some torque.

 

the issue really isn't the amount of torque, all the problems with the 6 speeds are in the hubs/shift linkages.

the Fiata used the old 5 speed from the SA/FB/NA/NB/NC

 

Fiata is most definitely a 6 speed, as is the NC Miata for anything but the first few years of production. The Fiata uses a version of the NC Miata's 6 speed, which is extremely similar the the series II RX8's 6 speed.

https://www.automobilemag.com/news/2...x5-miata-club/

https://www.caranddriver.com/reviews...mparison-test/

One of the most common failures of the series I RX8 6 speed is that if you sneeze at the wrong time the synchros will fall apart. There is also a known issue where 4th gear will eat itself. The series II 6 speed is relatively problem free and very similar to the NC Miata 6 speed.

 

For street driving on a lower powered car and a driver with mechanical sympathy, I suspect that the 6 speed will do OK - at least for a while. A few people on here have done the swap although they don't post much. Also Rotary Performance in TX did a few.

Many of the comments above are inaccurate or have way too much hyperbole so anyone reading this should do more research beyond this thread.