Nissan Motorsports limited slip diff in my B310?

[mrmark]

I tracked down the previous owner of my car and he had so much good info about my car!  But the most surprising thing was the diff, I'm not sure what to think.  I've never heard of a limited slip for a B310, I just thought everybody welded the spiders for track use?  I'm not sure how limited slip it is as I put it up on a lift and I can't get it to slip at all.  I even had another guy hang on the other wheel trying to not let me turn the other.  I would have to guess that's it's a valuable unit if it is to be true but I'd like someway to ID it before I make any real claims.  Can anybody help me ID it?

[flatcat19]

While running, and both wheels spinning, take a prybar and try to slow one of the wheels down. You'll feel it knock/slip. 

 

 

Removing diff will also be the tell-tale. Post pics. 

[Lockleaf]

If lsd both wheels should spin the same direction if you have them off the ground and spin one side by hand. On open diffs they will spin in opposite directions

 

Unless you mean lsd instead of welded. Can the car drive or be pushed? Turn really tightly, if wheel hop, then welded. If smooth, LSD or open.

[Stoffregen Motorsports]

That would be a pretty valuable unit. I don't know if they made one for that axle, but I wouldn't be surprised.

 

You can shim the clutch pack in a clutch type LSD and I wouldn't be surprised if someone did, after all, they were performance minded enough to buy a LSD. There are a couple different ways to get more breakaway pressure out of a unit. One of the tricks is to simply turn the concave washers around so the concave face is pointed the other direction then simply reassembling the unit. Another is to physically cut shims out of shi stock. A third way is to buy thicker shims from the Datsun Comp/Nissan Motorsports/Nismo catalog. A fourth way is to cut the carrier on a lathe to bring the mating surface closer together.

 

If it's really tight, it could be because it's damaged. The wrong gear oil can cause wera over time and gall the spring shims, essentially locking it up. You need to run a special LSD hypoid gear oil with friction modifiers in it.

 

It may be that the only way to positively ID it is to remove the diff. It's not that hard. Can be done in 20 minutes.