I recently purchased a 91 S5 automatic and plan on converting it to 5-speed. There are several transmission options available to me locally and I do not plan on installing a Turbo II for the foreseable future. I have previously had an S4 and S5 5-speed and the one thing that I did not like about my S5 was that the gearing was too tall. My question is should I install the S5 (possibly modding the gear ratios ) or just use an S4 or do the Miata transmission swap into an FC bell housing ? The car will be DD, auto-x, and some HPDE and other track days. I will be looking at a car this afternoon that has an S5 5-speed.

** I understand the auto to manual transmisssion isn't a straght swap. My question is more about gearing as I felt that if my S5 had my S4 transmission, the car would have been a lot more fun **

 

The gearing is pretty much identical between the S4 and S5 -- the only difference being earlier S4's with a different 5th gear.

 

Yeah gearing does not feel different I had an s5 it ate itself so I swapped an s4 and noticed no difference. just make sure you get the right mount. Though auto swap is more complicated.
S4 has two bolt holes on the bottom
S5 has four bolt holes, two on each side.

 

Don't know why but my 88 SE 5-speed felt peppier and I assumed since the 88 had less HP than the S5, that this was down to the gearing between the different transmissions. Was going to look at a 91 5-speed today but had to reschedule. I think the NA 13B would be better with shorter gearing per this thread.

https://www.rx7club.com/2nd-generati...esults-481920/

Does anybody have any experience with aftermarket gearing in the S4 or S5 transmissions ?

 

Most people just upgrade to the turbo trans.
n/a is so weak it not worth the trouble even with stock n/a power they are a time bomb.
Maybe when you swapped trans your old one was trashed and the s4 was just in better condition and placebo kicked in.
Better off upgrading diff if you want to mess with gearing.

 

I know the turbo II transmission is stronger than the NA but is the gearing similar also ?

 

Gear ratios:

https://www.mazdatrix.com/g1.htm

 

Cool, thats exactly what I was looking for. Thanks