Turbo vs NA vs 1st gen diffs
 

Hi, my first post in about a million years....

I've got a '90 Turbo rally car, and am chasing a low ratio (numerically higher) diff for it.

I know I can get 4.375 ratios from the states, but by the time I get one here (Australia), the price is horrific. Some searching has shown that it APPEARS that your non-Turbo 2nd Gens have a diff centre that is very similar to the 1st gen style (knowing that the 1st gens are not IRS!).

I happen to own a 1st Gen LSD with a 4.875:1 ratio, which would be perfect... The Australian non-turbo 2nd Gens came with the Turbo brakes and diff, so I can't go and check...

So (finally getting to the point :)): Will a 1st Gen centre fit into a 2nd Gen non-turbo alloy diff housing? I'm not concerned about tail-shaft interchangability, but fit into the housing and rear half-shaft fit is important!

Thanks in advance, any help welcomed! :)

OK, so I've done a search, and I saw some-one mentioned that Mazdatrix sells a "pinion adaptor" to fit some sort of 'foreign' CW&P into a 88-92 diff housing. I can't find any mention of it on the Mazdatrix website, so I'll have to continue with the dumb questions... (sorry!).

1. Is this to fit the NA or Turbo 86-92 diff?
2. Which CW&P?

"nudge".

Anyone? Please?

What do people do for a decent diff' ratio for 2nd gen's?

Or are there possible interchanges with commercial CW&P available that anyone can tell us of?

you can go to http://www.mazdatrix.com/g8.htm
and look at the bottom of the page .there you can see that all the N/A ones from 84(1st gen) through 92 share the same torsen diff.i think that means the same diff center.
as far as the australian N/As came with the turbo's stuff,why don't you just fit the 1st gen's (4.875) ring and pinion to your 2nd gen diff center?

ok, the way im reading this, is that you want a better gear ratio in the rear(am i wrong?). the accual "diff" unit will interchange but i do beleave the accual "gears" are different, the pinion gear has a longer input shaft on the second gens(i think). now, if you could some how make the whole third member fit into the alloy diff housing, you could do that with a custom lengthened drive shaft, i beleave it may work cause i seem to remember hearning that an mx5 third member would bolt up to a first gen axel housing with minor moddifications.....

Thanks for your help guys.
OK, so it now appears that the solution is:

1994 MX-5 (Miata) pinion carrier
1994 MX-5 or NA RX-7 housing and stub shafts.
Custom plate to mount short MX-5 carrier into RX-7 body.
4.875:1 CW&P from early car (I have one already!:)).
Early LSD (have already:)).
Non-turbo RX-7 half shafts.
Custom tail-shaft.

The big question I now have is how many splines are on the 1800cc MX-5 stub shafts. I'm assuming the answer is "26 spline", seeing as the last 1st gen RX-7s had 26-spline and the NA 2nd Gens have the same LSDs.

Anyone know?

I think you're best off w/ a pinion extension.

I agree. But I couldn't find any reference to them anywhere, inc the Mazdatrix site.