Differential testing
 

If, with the car jacked up, you turn one of the rear wheels in one direction the other turns on the same direction you have limited slip; if it turns the opposite direction you don't have limited sliped but a standard differential.

The question is: What do you have when you turn one of the rear wheels and nothing happen to the other wheel??? On another words, you can turn either one of the rear wheels in any direction and the other one does not move.

You have a broken differential;)

I don't think it is broken, actually.

I think you have an open differential.

Do you have the car in gear? If yes and it does this, then I am not experienced enough to tell.

If this is an early car, make sure you do not have a failed "simplified" differential

Edit: 901 posts :-)

Parking brake partially engaged perhaps?

If it's in gear and this happens... it's broken.

The car is in neutral, and you can turn one rear wheel in any direction and the other one just sits there...

While running there is no noise at all, plenty of power, excellent handling... the whole things appears normal. Puzzled???

Spinning one and watching the other usually but not always works. There is some preload that is sensitive to input torque.

Have someone hold one while spinning the other, an effective lsd will make that difficult to do. An open or worn out lsd will not present much resistance.

Put it in gear, too.

If it's in neutral, you're just spinning the tranny guts instead of the opposite wheel. Put in in gear like Flieger sez.

I was at the track this past weekend for the PCA Club Race and noticed that almost all the 911/GT3/GT2 while on the jacks warming up (engine running) and fine tuning - in neutral - had the rear wheels spining, slowly but spinning... both in the same direction. However, there where some others - on the same mode - but the wheels were still. Why the difference?