I just took my 1985 13b trans and a 1994 Miata trans to the trans shop
to have the guts swapped. I have heard that they are identical
and the input shafts can be exchanged. On mine the bell housing and tailshaft housing
can be swapped but NOT the Input Shaft.

The gear count is different and the dia of the shaft going into
the back of the input shaft is larger on the Miata.

So the Miata shaft must be modified to work in the
RX7 bell housing.
The Miata shaft is longer and the splines are further from the
trans. I took both shafts to a machine shop they said they would
grind the Miata shaft to work. $ 100

 

thats what you have to do. is nothing new

 

rlinbren, which machine shop did the work?, and were you happy with the work they did?

I need some machining done on my transmission,and looking for a good shop in / around El Cajon.

thanks, Michael