Differential Identification & Swappability Help Please
 

Hello, I'm in the process of replacing my differential that croaked. The replacement didn't come with flanges, so I pulled my old ones out only to discover that my original has a vertical shaft inside, while the replacement has nothing.

I have a '91, and supposedly the replacement differential also came from a '91. I'm hoping for some help identifying what I have now and what my replacement is, but ultimately wondering if I can do a direct swap without getting new axles etc.

After reading the differential spotter's guide (http://www.miata.net/garage/diffguide/index.html), here's what I'm thinking:

Mine: identical flange tabs, vertical spider shaft, no rubber damper = 1.6 open differential (non-Torsen)?

Replacement: no vertical spider shaft, no rubber damper = 1.6 torsen?

If that's true, since they are both 1.6, I'm just replacing a non-torsen with a torsen and it should work as a direct swap, yeah? Or do I need new axles and drive shaft since the replacement is a Torsen?

Well, there was no TorSen offered in the 1.6. The only options were open and viscous limited slip. The viscous limited slip used a thick fluid to transfer the energy to the non-spinning wheel. It works like having a large bowl of honey and trying to stir it quickly without holding the bowl. The bowl will try to spin. One of them will be a VLSD and the other is open with spider gears.

Ok, thanks for your help! I did discover the new one is a VLSD, so I'm having to find another diff and hopefully return this VLSD, or if I can't, find someone who wants it even without the axles (is that likely?)

Why ditch the VLSD? It is better than open. Are you switching to the 1.8 rear instead?