You have to shave back the splines from the tip of the input shaft. Roughtly 1/2". So the input shaft tip looks the same as FC. That is all. No biggie. Cost me fifty bucks to do mine (626 tranny though).

 

yeah, the cost of resplinging the shaft really wasnt much for me either...i think sixty bux, iirc.

 

This swap has always surprised me.. I race a Miata in CSP and I feel that 1 and 2 are way to tall and the acceleration in poor. My Fc's have always seemed to have a "better" ratio as far as acceleration goes. It may be in my head, but my FC's always finish in the same time bracket as does the miata. I was running stock suspension vs. A full racing beat setup on the miata.. I know the car itself is faster... but.. I am rambling.

I think that a OEM tranny with a lightweight flywheel, and upgraded clutch would probably give a similar result with less $ and or fabrication involved. Or just purchase some different gears, they are out there.. There is always a GTUs rear swap... Just an opinion..

Congradulations on the swap, it really shows what someone can do with enough money and fabrication knowlage.

 

having driven both setups, there is actually quite a noticable difference between the miatabox/aluminium flywheel setup and the stock tranny/aluminium flywheel setup. a lightweight flywheel will help you rev up quicker, but it wont change your gear ratios.
the miatabox has shorter gear ratios, and when paired with the fc motor, offers significant improvement(most notebly on 2-3 upshift) for road racing. now, i havent tried any autox, so i cant say with certainty how the car would perform in a situation like that. im speaking from a road racing perspective(and street driving as well).
now i havent tried driving anything with a 4.3 either, that would be an interesting comparison.

does anyone with a 4.3 plan on going to mazfest?

 

I am planning on Mazdafest.....but I run stock s4 trans with a 4.88 rear! Wish I had the money for a 5.12 though!

 

sounds cool-whered you get the 4.8 from? i assume since your driving all the way from sf that your going to be driving, right?

 

Yeah I should be driving both days. This will be three years in a row for Bern's events! The 4.88 is from Mazda Motorsports. It fits a 1st gen, and you have to get the pinion modified to fit a 2nd gen.

 

sounds nice id like to check out your car, so hit me up, ill be there both days.

 

i hate west coast ppl

 

dont hate-appreciate!

or...come visit! im excited to see the car perform after all the changes ive been making...mazfest should be really fun-you should come on out

 

im from ohio and live very close to mid-ohio
i think after all the good feedback on your
post that a miata box is in my future
thanks for all the good info

 

mid-ohio is a BEAUTIFUL track. i was lucky enough to be their as a crew memeber during last years SCCA runoffs, and i hope to be back in the future for the NASA nationals

if you do the swap, id love to hear how it goes

 

i found 2 miata trans 90 and 93 is there a setain year box i am looking for?

i also found 2 s4 n/a's with lsd diff's i got a gxl with 4:3 gears so the miata
box will work like a charm

 

either the 90 or the 93 should work fine, but the 94-98 boxes had slightly beefier gears, thus they are stronger. 4.3 with the miata gears sounds really nice

 

so whats the difference between the miata swap and using a 12a? they are both sorta the same in power acceptance, and they both have closer gears ratios....

 

81-83 RX7 : 3.674 2.217 1.432 1.00 .825
84-85 RX7 12a: 3.622 2.186 1.419 1.00 .758
Miata: 3.13 1.833 1.303 1.00 .840


theres the difference

 

lol second and third are almost the same damn gear.

 

second and third is where i feel the most difference between the miata tranny and the FC gears. i dont know about a 12A tranny, ive never heard of anyone putting it in an FC. i do know that alot of race cars swap from the 12A tranny to the miata tranny, and i know that 1st gen trannies are wearing out and replacement parts can be hard to find, so thats probably part of the reason right there.

 

im sure ill being grabbing a miate trans if one ever strolls through the junkyard, but they never do even with the 834879594 of them near me.

 

For racing the Miata ratios are probably better, as you're not having to go into first at all, so the taller ratio isn't bad. On the street the first gen box may be better, as it has a lower 1st gear, giving better off the line acceleration. It's really a matter of personal preference and intended use though in which one's "better". One thing the first gen tranny has going for it is the ease of conversion, there's no machining necessary.

 

exactly-when im on the track, i dont use my 1st at all. on the street, even with an aluminium flywheel, its REALLY not bad...starting/traffic/hills arent any more of a problem than they were before...and i take the 405 to work every day

 

im still looking for a 94-98 trans
do you think it could hold 200 hp im using
a 235/45/17 nitto 555's with a 4 puck
i have herd mixed reviews on how strong
this box is any max hp/torque numbers out
there?

 

i cant give you exact numbers, but i can say that the E Production FB that i crew for is putting out over 200 hp, on racing slicks, and his miata box handles it fine.
arent nito 555's drag tires? i might be mistaken...

 

the nitto 555 is a street tire they also have a street slick called 555R
same tread pattern different compound

 

Drag racing will make any transmission break at a lower torque than just street driving, or even autocrossing or road racing. It's the shock loads that really hurt it. With slicks and 200hp drag racing would probably be about the limit at which I'd feel comfortable saying that it won't break. With normal driving it should be good to around 250hp, beyond that you'll need a stronger box. Many Miata owners with lots of power use TII gearboxes.