Hello everyone! I looked around for awhile amongst the many threads available, but I can't seem to find the right place.
I'm looking for a guide or a list of needed changes along with a straight up answer if it will even work.

I just got my rx7 fd and I'm about to pretty much finish the car but I can't help but imagine it would feel pretty smooth.

I want to be able to keep the gear ratio of the rx7 fd with the 6 speed. Any feedback tips or just straight honesty is completely appreciated!

 

welcome to the board.

here's a chart so you can look at your gains and losses: https://mazdatrix.com/transmission-a...-ratio-charts/

as for the swap, you will obviously need a new slave setup. both because of location and the fact that the Rx-7 uses a pull-type clutch. i'm not sure what else would be needed to convert to a push-type setup, but that is what the Rx-8 tranny is. due to interference with the engine oil filter, you can't use the Rx-8 slave. the Gen 3 Acura Integra slave is the one that i think others have said will fit. you'll probably want to confirm that with Pineapple because i think i recall reading somewhere that they were putting a kit together. i don't know if they have done so yet.

www.pineappleracing.com

mounting may be an issue as well as i doubt the PPFs in the FD and FE line up exactly, but it shouldn't be as complicated as mounting it in an older Rx-7. ultimately, i don't know for sure.

from everything i have read, the S2 Rx-8 box is stronger and able to handle more torque (compared to the S1 6 speed). however, it seems to set itself apart from the old R-box in that it is similarly capable, but it doesn't mind high revs while being stressed.

hope this helps you some.

 

Just an FYI, the RX-8 six speeds have a top gear that is about halfway between an FD fourth and FD fifth. First and second gears are very similar, FD 4th is the same as RX-8 5th.What the 6 speed gets you relative to the FD trans is an extra gear between 2 and 4 and a shorter overdrive gear for less RPM drop-off.

if you want to keep a similar top gear, you would want to swap to an automatic final drive at the same time, IIRC those are 3.91.

In this case, more gears doesn't mean more spread from bottom to top, and it's actually a shorter spread. What you get is closer spacing between all the gears... except for 1-2 because I think ALL Mazda transmissions have a 60% ratio change 1-2 so that 2nd can take you all the way to 60mph for the magazine tests.

 

This may sound stupid and some may say unrelated or unrealistic but a few years back I did a test in Gran Turismo by using the custom gearbox which at that time let you put a 6 speed in and FC. I changed the gears between the stock n/a, stock TII, 5 speed Miata, and 6 speed Miata( which has the same ratios as the S1 Rx-8 except for 4th gear). I drove all of them around the same track in game. My results were of the factory Mazda options the Miata/ Rx-8 performed the best on track. All tests were done with a 4.3 rear end ratio if that matters. I know it's a video game but it did give the ability to test all options in the same car and look at how the rpms dropped between each gear change.

Edit to add. I change the above text after finding my original thread where I did this test. I doubt the S1 4th gear or S2 ratios would perform any worse though. I may need to do another test to compare the two.

 

there’s a lot working against it

the shifter position difference between an FD3 and RX8 is about 3”, the Rx8 box shifter location being shorter due to the Renesis engine being slid back further in the chassis.

the RX8 box will shred teeth off gears easier than the REW box as well and you’d need to not abuse it hard, the RX8 box PPF position and mounting is different than the REW

you only need a 225mm push clutch setup to handle the torque, including the slave, it will bolt right up to an REW engine otherwise. Which is a common swap into the RX8 chassis. It all lines up and bolts on going that direction along with an aftermarket engine mount kit. Not so easy in the opposite direction as you’re asking for.
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