Are there any differences between these differentials?
I have a 3.90:1 and don't know if it came from a 10th anniversary or a Mazdaspeed, now I need half-shafts so I need to know which shafts to buy.

The 3.90 that I have has numbers cast on the left side "MA02 4 PA" and painted at the bottom in white "3818" and a couple of dash marks hand painted in white on the top that look like number eleven. It has 26 splines inside the diff.

 

Mazdaspeeds didnt come with 3.9's.

 

Thank's for the info, I always assumed the Mazdaspeed had a 3.90 because of the 6 speed transmission. Found one on Ebay Mazda Miata mazdaspeed Differential MX5 4 10 1 Ratio | eBay that confirms they are 4.10:1
Due the 3.90 diffs form the 10th anniversary use the same one piece half-shafts than the rest of the normally aspirated post 99 miatas?

 

Yeah. Do more research.

 

yeah

 

Only Mazdaspeed diffs and axles are different. End discussion.

 

Ok, will get regular one piece shafts from any NB1 NB2 exept Mazdaspeed.
Thank you.

 

99-03 6spd cars had 3.9 diffs. for sure. Pretty sure all 04-05 6spd cars had 4.1 like MSM (but MSM had larger axles)

 

None of that matters because all he was trying to figure out was what axles to get.