Alright, I've done hours worth of searching and am getting mixed answers.



I have a 1984 GSL-SE rearend. I have everything except the 'pumpkin' / differential. On to the questions:



1- Does the GSL-SE use larger axles and more splines than the GSL?



1a- IF the above is true... are the 81-83 axles the same as the 84-85 cars?



2- Will the Miata (NA & NB) differential fit in the GSL-SE housing?



2a- IF the Miata diff does not work, what will?

1) No same **** as long as it's 84-85. But the se lug pattern is different



1.a) false the older **** has smaller berarings and aren't interchangeable with 84-85



2) not sure man?



I don't know what direction your going with your fb? but in my opinion fb rears arent the strongest especially for drag.

the 84-85 rear ends are all big axle, in addition you can swap spider gears in the diff and change big to small, and small to big



i have seen pictures of the 94-05 miata pumpkin into a 1st gen housing, you need to grind some stuff off of it for the watts linkage



http://www.rx7.org/jes/

Thats some interesting ****. It all depends on what your building your car for? autocross. drag, or multi purpose.

some of those miatae have 4.30 gears too

bigboi, I'm not drag racing the car. if I was, I have a '73 9-inch waiting for a project.



the cars purpose will be road course racing- most likely spec rx-7, which is why it has to be a Mazda part.

doesnt spec 7 mean you've gotta run a stock 12a 3.9? miata comes in that flavor too



i notice we missed this in the first post, if you have an 84-85 disc brake axle housing the stuff that makes it a gsl-se vs gsl are the following



1. brake backing plates calipers and rotors are different (-se is vented, so the rotor is wider)



2. the axles are different, same diameter, but the gsl-se has the 4x114.3 bolt pattern for the wheels, while the 12a is 4x110



3 pumpkin. the iron housing is the same from like 1968 to 1985, the 84 gsl-se's have a 4.09 ring and pinion vs the 3.9 of the 12a. 85 gsl-se's have a 3.9. gsl and gsl-se limted slip units are the same, except the gsl-se is setup to be looser stock (they flip something around in the diff). the miatas use a torsen, with either a 3.9, 4:10, or 4.3 gearset.



mazda generally matches the rear end to the diameter of the tires.

Basically, I have a 1984 GSL-SE, with all the rearend parts needed except for the differential and diff housing- which I mistakenly sold. It does have the larger bolt pattern and vented rotors. I believe it had 4.10 gears.



I'm not 100% sure about the spec 7 rule. I am also considering SCCA IT racing (if I can't find a rotary engine). Such is the world of racing, the more mods you do bumps you up to the next class.



At this point, I am considering the Miata or B series diff with 3.90 gears and a nice limited slip diff- clutch or torsen.



thanks 'j9fd3s' for the help.

look at the rules, SCCA is weird...



if you go over to NASA, they have two classes, time trials TT or the performance touring PT. both classes use either a point system, or hp to weight to class you. TT isnt wheel to wheel either, so you can build a nicer car

"TT isnt wheel to wheel either, so you can build a nicer car"



LOL. that is true. my FB will not have a high end paint job and I will have spare body panels.



I'm still searching for a diff.