do i need the matching tranny? I'm pretty sure i can just swap the speedo gears, but wanted to double check. I want the speedo to be as accurate as possible. Thanks

 

nope but the right driveshaft - meaning it has to be a post-82 due to wide 3rd member flange.

 

my car is an 85, so i have the driveshaft covered. basically i just want the 4.09 gears and the lsd (i might even jsut go out and get a torsen). I'm building the car for CSP auto-x, and need to make sure all is legal.

 

If you want the torson, go for the 99+ miata. The whole diff is interchangeable with ours, it has 4.30 ring and pinion, and the beloved torson. I believe it is the auto version but someone needs to confirm that...

 

i can't use the miata gear, as it was not available on an 85 rx7. thanks though