okay. i have a 12a trans, a GSLSE with no trans at all. and a S4 NA trans. ive heard that each trans will work by just bolting them up and ive heard that each will not. i do not have the original transmission to use anything off the GSLSE trans. So can i frankenstein the 12a and S4 trans to make it work? or what is the truth behind this.

 

It bolts right up to the engine. However, the FC trans - the only problem with it is the shifter. You will need to cut the current shifter hole larger - about an inch to inch and a half so that it will work correctly (cut towards rear of car). As far as I know, this is the only thing needed to make an FC transmission go into an FB.

 

The only different trans that was available in an RX-7 was the TII and 3rd gen trannies. These use a different number of output shaft splines and will not work with any N/A driveshaft. Other than that, its just the shifter position thats different from 1st to 2nd gen. All will bolt up to any rotary.

 

Yes!

 

You can also take the tailshaft housing off the 12a trans, bolt it to the S4 trans, and not cut the floor.

That said: A 12a trans will hold the power fine, and make your car quicker than S4. The S4 will give you better mileage on the highway.

That is the real choice you have to make

 

i think the 12a might be the best choice then.