So I have a GSL-SE 5spd trans apart that I'm having rebuilt for a customers car, I ordered a full syncro and bearing kit, but my buddy who rebuilds trans pointed out the main shaft and 5th gear shaft both have bad pitting and wear.

Mazda shows no stock on either shaft.

Would the FC N/A trans internals be interchangeable? Or possibly Miata trans?

Joe

 

FC stuff wont work.

Not sure about Miata.

I think all the FB mainshafts should work. I can't remember anything on the main shafts different between the 4 parts trans I have.

Might have a good main shaft for ya cheap.

 

i think 81-85 main shaft is the same? off the top i think the FC uses a different needle bearing between the mainshaft and the input shaft

the miata should use the late one too, but you should check the bearing part numbers

 

I just looked it up parts catalog. The 12A and 13B use the same shaft.

Parts numbers:
M502-17-221 from '81 to Sep 84
M502-17-221A from Oct 84

Not sure what the change was for the 85 model

 

i do know the main shaft from 81-84 is the same, regardless whether its a 12A or 13B trans. Chris is right that there's a change in 85. the diameter and length is still probably the same. it may just be a minor cosmetic change.

 

i vaguely remember that the parts fische is wrong. this was in the 90's but i think one number is the 4 speed shaft, and the other is the 5 speed? i know this cause we ordered one.... but this was like 15 years ago... i wanna say that the late number is the 4 speed one?

 

I thought they dropped the 4 speed in '81? I didn't post the numbers for the 79-80 because they were completely different numbers and I figured different parts.

 

i know, i think thats why i remember it?

 

Good info guys, I looked around in my parts collection and do not have an FB trans to take apart, so if anyone has a good main shaft and 5th grear set to selll let me know!

Thanks

 

The 5th gear set is different in the SE than the 12A. It should still work but the ratio will be different than stock. This should help: http://www.mazdatrix.com/g1.htm

You should put a want ad up.