Surefire way, try and do a donut. If all it does is unload one tire to spin as you're going in a circle its an open diff. Limited slip cars will actually whip around on dry pavement.

 

What if the car is on 22s and has a turbonator?

 

True or not true, because I had this chat with someone a while back:

With a torsen, car in neutral, you can't turn both axles by hand in the same direction unless the speed of the two sides matches exactly. This is because the worm gear parts that make it a torsen can't easily be back-driven while the torsen is in action.

Again, true or not true? I unfortunately threw my torsen in without looking through the axle holes, so I'll have to rely on the donut method.

 

Well I've yet to see a miata with 22s and a turbonator so I can't answer this... if it has somewhat normal size tires the car could actually spin the donut method should work.

 

Bzzzzzzzzzz. False.


A torsen CANNOT be tested in the air/on jack stands/on a lift by just turning the wheels. If you have the car in the air to see if it has LSD, you'd better be pulling the axle as TorSen LSDs pretty much turn into an open diff as soon as one wheel comes off the ground or is on ice.