s4 n/a motor s5 trans????
 

i got a 1988 rx7 thats needs a new trans. will an s5 trans fit on a s4 motor?

Yes. The only difference is the 5th gear is a bit shorter. I'd replace the front and rear seals before putting it in. It sucks to take it out later down the road to fix a tranny fluid leak when you can fix it for $10 while it's already out of the car. Preventative maintenance FTW. Check mazdatrix.com the seals.

Ensure you use the s5 transmission crossmember.