Swapping an NA S5 auto to manual and it is time for me to make my final pick of which tranny to use. I have both from a 1988 S4 GXL NA 5 Speed and LSD Rear From the NA GXL as well. I Have chosen to use the LSD Rear from the 1988 GXL. "because it was free and i had it " I also have a turbo 5 speed tranny 1987. noteing that Mazda trix has a Drive shaft that can be used with the turbu tranny and keep the NA rear as the engine will be NA . And of cource i will have to get the proper fly and clutch etc.. for the S5 NA engine. Ever what flavor I choose NA tranny Or the Turbo Tranny.
My question is what are the pros and cons for using the turbo tranny vs the NA tranny in the S5 NA car. If you had to choose between the two Which one would you choose to use and why? Keep in mind I want the best preformance i can get from the car.
S5 NA full street port

 

The na tranny should be strong enough for what your doing. No sence in going through the extra work to put the turbo tranny in. Unless your driving style is spinning donuts every parking lot. The turbo tranny is a little stronger but just the street port na I would keep it simple.

 

if either way you have to buy a driveshaft then use the t2 but if you have the driveshaft for the NA then put the NA in.

 

Are you going to turbo the car in the future?

 

Im going to keep this car NA for now if i go with turbo i probably will get a second car turbo prob s4 turbo 87

 

The NA is sufficient to handle your SP. The gear ratios are slightly different but you probably won't be able to tell the difference.

86-88 RX7 Turbo 3.483 2.015 1.391 1.00 .762
87-88 RX7 Non-Turbo 3.475 2.002 1.366 1.00 .697

You want the best performance? Change the NA box to Miata gears. Otherwise, just use the NA box as is and save the $ on the driveshaft.

Miata Gears - http://www.mazdatrix.com/faq/miatainputshaft.htm