Can a Miata/mx5 lsd diff fit an rx7
 

Read a lot about this, got to my local dealer and fetched a LSD rear diff from a 2002 Miata. Fits the ring gear, but the axles doesn’t fit, the rx7 axles are too small.

is it possible to get one that fits without issue ? What do I need to search for ?

my Rx7 is a 83’ 4x110 and rear disc brakes.
https://cimg3.ibsrv.net/gimg/www.rx7...f0c9f17f3.jpeg
https://cimg4.ibsrv.net/gimg/www.rx7...198a9c62b.jpeg
https://cimg5.ibsrv.net/gimg/www.rx7...5801137a9.jpeg

26 spline axles from 84-85 12A engined cars should fit. But you'll need the whole axle housing because they have bigger bearings.

damn, so basically a complete new rear axle ?!

can’t I find another miata diff that’s fit in my axle with the small splines ?

No. All 7" diffs before 1984 (maybe back to a certain point) are 24 spline, all 7" diffs from '84 up are 26 spline. This is across corporate, not just RX-7s. Even the front wheel drive transmissions are 26 spline.

Shiiiit! So much for this being an easy swap! :(

There is no Miata 7" diff with 24 splines then ?

Anybody with a rear axle with big axles in europe then ? :D

I think the 6" diff from the '90-93 Miata is 24 spline but this of precisely zero help. They were all open diff or viscous diff anyway.

You may be able to find someone with 24 spline limited slip side gears for sale, those should plug right in to the Miata unit. Or you could have axles made with 26 spline on one end and small bearings on the other end, my measurements say it should work.

I Guess the 24 Spline side gears from the 6" Miate wont fit at all ??

Who and Where do I search for the right 24 Spline Side gear for the miata LSD ?

Any side gear from an '81-83 limited slip will work. I am pretty sure that Mazda only put them in RX-7s.

i might have a set, Mr Camicia is retiring, Gunn Auto Tech
and he gave me some stuff, one of which is an LSD without the case that was the classroom demo

Are the miata torsen side gears really the same as the rx7 clutch type? I have never taken a torsen apart, but it doesn't look like they are the same when peeking in at my spare torsen. I assume the 2002 miata lsd is a torsen?

Carl

Were small axle LSDs ever offered in Europe?

From a bit of googling their top trim model in '84 was SDX which had the 4x114.3 wheels but still had an open diff.
All European models from '81 had rear disks standard so they've got that going for them.

Did you ever find a solution to your LSD situation? I am likely getting out of racing RX7's (to race Miatas) and have a spare 24 spline clutch type LSD. If your 2002 is a torsen I would consider a trade. Let me know if you are interested.

Carl
https://cimg9.ibsrv.net/gimg/www.rx7...0b4c1bb699.jpg

Shipping to/from Denmark may be steep, perhaps Hummel206 would be open to outright buying it?

Hi Carl, No I didn't solve my issue, kind of gave up. I still have the Diff and are willing to trade or buy yours if it is inside my budget. My LSD is with two springs in the middle and some sort of friction plates between the housing and side gears, I don't think this is called a Torsen, but I have read contradictive information online.

Let me know if you wanna trade or Sell.

Pictures of my Miata diff. Up for sale :D

https://cimg5.ibsrv.net/gimg/www.rx7...090fdfa47d.jpg
https://cimg6.ibsrv.net/gimg/www.rx7...50d8c0ff2d.jpg
https://cimg7.ibsrv.net/gimg/www.rx7...19d5f0103c.jpg

I just checked and your diff appears to be the Tochigi-Fuji Super cone clutch type LSD with 3.636 gear ratio (based on MA02 stamp on ring gear). This was apparently available in the 6-speed 2003-2004 Miatas, although I think the LSD "came out" in 2002. That isn't ideal for my race class as I can't normally use the 3.636 gear ratio and the Fuji LSD isn't as durable as the torsen. I could use it as a track-side spare though if you are interested in swapping for the 24 spline LSD unit. I believe that shipping for the LSD unit pictured would be about $150 through USPS. According to a surfing buddy that is from Denmark and ships stuff back and forth regularly the shipping should be similar cost from Denmark to US through the Danish postal system.

Let me know.

Carl

If you prefer you can PM me.