Would like suggestions on how I identify which rear end I have on an NB1 Miata. When I purchased seller told me that I have a Torsen rear end but I would like to confirm and find out what the gear ratio is. Any suggestions on how to identify would be appreciated. Thanks in advance!

 

Why do you doubt the seller? Have you tested it on a loose surface, and found only one skid mark? Does it rattle? Where I come from, road car LSDs are almost invariably Torsens, the clutch packs being found in the hard-core racecars. I don't know of a way of distinguishing a clutch pack from a Torsen, other than the rattle, but then I haven't looked for one.

Simplest way of identifying the diff ratio is to compare revs in top with a car with a known ratio and the same gearbox. You can do the math, or there are calculators, using your own observations of revs. You can jack up one rear wheel, turn the prop shaft exactly ten revolutions and see how many revs the rear wheel does.

 

See above. Make the tires spin and look for matching skidmarks and calculate with engine rpm.
​​​​other methods:
A) remove an axle and peep into the hole, you could maybe pull the fill bolt and use an inspection camera?
B) spin driveshaft and do maths while watching how far the wheel spins.
C) remove entire diff and housing to count teeth

 

Thanks for the advice. I thought it would be simpler like looking for numbers on the diff. Then I am sure it is Torsen because it doesn't spin only on one side. I don't like the gear ratio because first gear goes to high revs very quickly but not much speed. In autocross I pretty much only use second and third gear. It's a five-speed and I'm wondering what the experience would be with different gear ratios.