Are all 3.9 lsd differentials the Torsen type?

[smy0003]

From the factory, yes.
But not all 3.9 diffs are lsd diffs.

[hks_kansei]

IF it is unmodified and is a factory LSD it will be a Torsen 2

However, it's fairly common for MX5 diffs to be chopped and changed, so if it's been opened up it could be anything from a Torsen, to a Clutch pack, to a spool or a weldy.

Spools and welded are usually advertised as such, since it's pretty obvious what they are.

Torsen or Clutch pack you'd need to ask them. (unless you can inspect in person, which is unlikely here)

[hks_kansei]

Allmaz are good guys, I've dealt with them heaps.

The reason they may not be 100% on the diff type is that they don't normally disassemble parts before sale (since if a part is in working order you wouldn't normally pull it apart unless you're rebuilding it)

If they say it's an LSD, i'd be confident it is.

It's most likely that it's a Torsen, since they were super common on MX5s (as far as LSDs go)
Torsen 1 or 2 is impossible to tell without pulling the diff open.

[greenMachine]

That's cool, found one, the guy says it could be from Japan.. I considered the 4.3 he had but going from a 3.63 nb8b 6 speed standard to this one I thought I might be going a bit too short in the gearing.


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Are you sure that is a 3.6 in your NB8B?

[noobee]

What else can be in an nb8b?


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anything that a previous owner has put in!
Mick

[smy0003]

Easy way to check is to just find some points where your speed and rpm line up nicely. For example, off the top of my head fourth at 60kmhr is exactly 2500rpm in a stock nb8b.
Then use the flying miata gear calculator to check if that is in line with the 3.63 diff.

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