3.9 open diff?
 

I tried searching but couldn't find much info. Did they ever make a 3.9 ratio non torsen diff for miatas?


Look at this on eBay:

1999 Mazda Miata Open Differential 3.9:1 Ratio Pulled Working Upgraded Save

http://bit.ly/Rr5NLE

No, they never made open 3.9 diffs. Furthermore, in 1999 it was only offered on 10AE miatas. So it's either a Torsen or a 4.1/4.3 open diff.

In 2003 there were the Fuji diffs that look like open diffs but are actually a clutch pack-type. I have one.

I am pretty sure they did. My memory tells me my spare diff is a 3.9 open.

Edit: Soviet beat me to it. Now I have to go look at my spare to see what it is.

The pictures make it look like an open diff (no large bushing) so the question would be what is the actual ratio. I think 4.3 came in autos that year?

Looks like a diff from an auto car, so assuming that no one has changed out the R&P, it would be open, but not 3.909:1.