Originally Posted by miataz
I wonder if there is any junk yards out there that there are 94+ miatas sitting out there with a torsen in them hmmm and the guys that own the place are dumb enough to not know about it and give it to you for very cheap, who know
There are indeed plenty of them out there. You'll need two things:
1- This datasheet: http://www.miata.net/faq/Miata90-97A3.pdf
2- (optional) This link: http://www.car-part.com/
Torsens were always part of a package on the Miata. So using the spreadsheet, you can determine based upon what options the car does or does not have, whether it was equipped with a Torsen. (Note that an automatic car never had a Torsen.)
For example, if you're looking at a '96, then any '96 with a leather steering wheel, power mirrors & windows, and a 5-speed will have a Torsen. R-package cars, which have none of those things, will also have a Torsen.
If you decide to search car-part.com, rather than local junkyards, ask for the VIN of the car which the diff came from. Then call Mazda USA and give them the VIN. They won't be able specifically to say whether the car had a Torsen, but they should be able to tell you what package the car was- which options it had. In my case, I called a junkyard in Arizona which told me that they had a burgundy '95 Miata. A call to Mazda with the VIN revealed that "burgundy" was in fact Merlot Mica, which made the car an M-edition, and therefore Torsen-equipped.
And there's nothing special about the hardware that holds the propshaft to the diff. The old 1.6 stuff will be too small, so just go to the hardware store and buy some class 10.9 replacements. I *think* that they're 10mm. That, or 8mm. It's 2mm bigger than whatever the 1.6 hardware was. The axle nuts are the only special item, and if you find axles with the hubs still attached, you won't even need to mess with those.