does a clsd need to sense torque in order to engage? Was junkyard strolling and found a 85 turbo 300. I jack up the rear and the diff spun as if it was open. I thought the turbo's came with a CLSD?

I am not sure about the Nissan version, but the U.S. brand limited slip differentials that I have owned would spin like an open dif when the car was up in the air with the AT in Park.

I seem to remember that they tended to be a little notchy, and took more effort to turn than a true open differential.

Most likely the 85 was an open diff, clsd's were first used in 6/87 and after turbo 300's

Rex

A CLSD should have both wheels spin in the same direction. But spinning wheels is not the correct way to check for any LSD. You must remove the rear cover and look inside.