lukearama

Has anyone used a Miata/MX5/roadster diff centre in there early RX series. I have been advised that its a bolt up option... Does the crown wheel and pinion shaft also fit in the Series RX? housing???



cheers Luke

thatpoorguy

I've never heard of anyone doing so as most here in the states swap stock diffs for dana's or ford 9 inch rear ends. Let us know if you find out for sure that you can do that.



Also, I love rally racing so if you have any vids please share!

Tri-Angles

So ford 9 inch rears can run normal street tyres? I though that you had to run deep dish wheels or slicks to run a 9 inch rear.

bigboi12A

Yup ive heared that that it works form some good people. I think it has to be 84-85 rear..



What Ive done is Kia Sportage 4X4 front diff. complete bolt in.



Pros and cons



Pro Miata diff has lsd

Pro kia diff is 4.77

Con kia diff is open so u need to weld gears not fun on the street unless your hadrcore

Con miata diff gear ratios i think arent as aggressive as the kia diff



Remember u need a 84-85 rear.



Kia front diff can be found real cheap i paid like 60 something dollars

Your car will pick up a tad more than a second in the quarter mile trust me.

thatpoorguy

Would it hold up though? Looks like the guy's going to be rallying it so it needs to take some abuse.



Most that use the ford 9" are using it for drag racing and have it custom setup and tub the rear, not sure what you'd have to do for running it rally....

bigboi12A

If u go the kia route the ring gear is cut different and way fatter than the factory diff.



way way stronger wont break. First hand experience: big street port 12a holley rb intake dual msd factory pp racing clutch disk. 13" mt slicks... on like 12 13 lbs of air big burn-out. kia rear holds car went 13.3 rx-7 it was



If u wanna rally factory diffs will hold dirt slips pave ment grips.... u just get shitty ratios with factory pieces



ford nine is heavy real real strong and u can get what ever gears u want even like 6.50. rally cars wana be light

thatpoorguy

Good call, I'd go with the Kia rear end too