It is a 9.75 if it is original. A posi can only make up for a certain % of traction bias. I have unloaded my inside tire in turns before overcoming the clutch frition. Posi is a helper but cannot overcome 100% traction on one wheel and 20% traction on the other. Even open diff cars will spin both in a straight line if you have equal traction and hit them with enough power. Once you turn you are likely to lift and one wheel peel. Torsen told me they are working on one for late 03 but it will not take high modded pwoer. Only around 500ft lbs tq. Just get it rebuilt or replaced if ou like and only run the amount of frition modifier needed to quiet clutches. Too much modifier lessens the posi friction. I had an Auburn Pro Series in my old truck and it was so tight it chirped tires during turns. I loved that unit The pro was about 400#'s more preloaded than their high performance line 800 vs 1200#.

 

I got an eaton when they first came out for my snake. Granted, i was leaving the line at 7K @ 18 psi, it lasted all of about 4,000 miles before it grenaded. The Detroit never failed me afterwards though.

Why not just go with a custom 9inch and call it done?

 

(I only understand this from way back when)
I believe the way to properly test a limited slip is to:

Jack either the left rear or right rear leaving the opposite tire on the ground. Then using a torque wrench on the raised wheel, measure the torque it takes to turn that wheel.

??

WOT