https://www.rx7club.com/showthread.p...t=jspec+ration

Ok, found this info regarding 5th gear ratio on various TII's trannys. I also found that Ted on FC3Spro says the 5th gear can be swapped out of FD's.

Question #1: Is the 5th gear ratio lower on the N/A and
Question #2 Can the N/A 5th gear be swapped in from the N/A to the TII tranny?

I am in the beginning of a swap Jspec S5 into S4 TII. I want the lower ratio of the Aspec, but my original tranny has lots of miles whereas the Jspec is much younger and fresher.

If I am going to swap the 5th gear anyway, I would like the even lower N/A ratio.

Is this a fit, has it ever been done?

I do lots of hiway driving and would like the lower rpm for hiway calm and also a little bump for efficiency.

Off hand, what is the revs per mile on TII Aspec vs. Jsped trannys, anyone?

thanks

edit:

Found the N/A Ratio in the FAQ. Duh. Looks like it is19'86 and 1987=.711 and 1987.5 up =.697.

Can the swap be made?

 

no.

 

You don't want to anyways.

 

If I could, why not? It would make about 400-500 revs per mile difference on the highway.

 

If you want to change just 1 gear out of the tranny, it's not possible without really good skills in welding and cutting. You'd be better off just switching out the whole shaft or getting another tranny, OR get a new differential with different ratios.

 

Hmm... not sure why any one would be welding on the tranny to change out one of the cogs, but then, I haven't been inside the FC tranny either.