Gen 1/ Gen 2 transmission swap
 

I've got an 88 GXL that i just spent a month tracking down parts to finish installing a new clutch set in, only to find out that the transmission has had it, and that's where all the vibration came from. A friend of mine has an 85 GSL, in which the tranny is about the only usable part. I heard from someone that it will fit on my FC3 if the tail shafts werre swapped. Does anyone have any useful info on this? Thank you

if i remeber correctly i think that by doing that your kind of down grading the car....i think the 1st gen had a weaker tranny..im not really sure though

I wouldnt consider it a downgrade but more of a hassle due to the fact that the shift knob wont line up the same.

It sure can be done. I've got an FB tranny in my car at the moment. It's lived through many street miles and about 5 days on track, so it's not that fragile. I did it because I liked the gear ratios a little better and it was cheap. Mine has an S4 tailshaft housing and an S4 front housing/bellhousing. I'm not too sure what the difference is on the latter though, but I don't think it's needed.

If you swap the internals into your existing housing then it's guaranteed to bolt in just like stock.

Wow... good info here... .I didn't realize that was doable!

whats the ratio for the FB trans?

Take your pick
79-80 RX7 3.674 2.217 1.432 1.00 .825
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
84-85 GSLSE 3.622 2.186 1.419 1.00 .807

Mine's a 0.825 5th one. It's nice to actually have enough power in 5th to go up some hills.

I'll probably be swapping it out for a Miata gearbox in the next year or two though, as it's stronger and has closer ratios.

I have no idea where people keep getting this idea that Miata's use shorter gears.
The fifth gear is shorter than the FCs, but EVERY other gear is LONGER.
How many of you out there actually use 5th gear on a race track?
How many use it on the highway?

If strength is the concernt, why just use a TII transmission?

S4 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697
S4 RX7 TurboII 3.483 2.015 1.391 1.00 .762
MIATA 3.13 1.833 1.303 1.00 .840

For a full chart of transmission gearing: http://www.mazdatrix.com/g1.htm

The miata gearset spaces first, second, and third gears together very nicely. A longer first gear would be very nice for hairpins when second gear is too long and first in the FC is too short.

^That is entirely dependent on the track though. Just depends on how tight "tight" is, and how fast you can take it.

As far as accellerating in a straight line, the RX7 gears are supperior.

I didn't say shorter, I said closer. I also meant stronger than the supposedly weak 1st gen unit. I don't necessarily need stronger, but it's nice to know that I'll no longer have a supposedly weak one.

I've never had to use 1st on track, and 2nd is usually up in the rev range anyway, so closer is better.

Im not trying to be a nay-sayer, but the RX gears are also close (except for 4-5) compared to the Miata. The only upside to the Miata gear set I could GUESS would be better syncros. The FD got better syncros than the FC, so I would assume that the Miata would too since it was produced by Mazda at the same time. The price of buying the gears, getting them swapped to the RX case, and reinstalling really wouldnt be worth the hassle or money imo.

EDIT ^^^^
Apparently I cant do simple subtraction you were right, Black91NA. The miata ratios are closer, although a lower gear. Sorry for the misinformation and disbelief.