Quick Miata gearset question
 

Is there any problem with the '90-93 gearset where it can't be used in an RX-7?

It seems that when a year range is specified, it's "1994-up" or "1800cc".

I know the 1600s had small rearends and the 1800s had RX-7 sized rears. What about the trans?

http://www.solomiata.com/Drivetrain.html

and in '94 with improved seals and a double cone 2nd gear synchro

so i guess that makes the 5 speed, 90-93 and then 1994-now... yes the new miata 5 speed is the same...

Well, I'll be finding out soon enough. Picked up an "early style" Miata transmission for a price that I could not pass up. I didn't need to eat lunch this week anyway :)

I was a little nervous when I saw that the Mazdatrix FAQ said to use a '94-up trans. Maybe they just wanted to ensure people used "the best"? The Solomata site also says that the '83-earlier trans is junk. I'd rate them as as FC, then '81-earlier (big gears), then late FB. At least, my '80 trans aged very gracefully, and not explosively.

The 1.8 trans is much better than the 1.6

If you ever get a chance to look at both gear sets side by side you will see why..

90-93 will work. Everyone just does 94 and up because of the synchros.

are the ratios any different?

They appear to be the same.

The miata gearsets only work in the NA RX7 boxes correct?

NA only

If you have a Turbo II you can use an RX-8 transmission, which has even better ratios. Ignore 1st gear and it's basically a proper competition gearset. The only problem with it besides the lack of speedometer drive is that it uses T2/FD sized flywheel diameter and input/output shafts. Only a problem if you have an N/A engine and vehicle with no simple way of changing that.

From talking to RX8 roadracing teams running "stock" motors(215ish rwhp), the origian Aisin 6-speed sucks. Even after upgrading most of the stock bushings ect with metal parts, they still don't last much more than a 50 minute race. The 09+ trans is MUCH better and lasts much longer before needing rebuilt, but they are harder to find and fetch much more money.

um every transmission breaks when you put it behind an engine and try to shift....

When I did mine, the guys at Mazdatrix told me a 01' trans was the best one. I don't see any reason why, but that's what they said.

I ended up finding one from an 01' with 11k on it for $375.