Jack up the rear end, put the t-case in neutral. (if it has one......) block one of the rear wheels, try and turn the other one.... see how difficult it is to turn the tire, and what direction the opposite tire wants to go. There is a specific torque rating to 'test' these..... but, I don't know the numbers on the dodge rear-ends..... the LSD's DO wear over time, and lose some efficiency..... rebuilding isn't too bad of an ordeal.....

 

Locker if it will be drivin on the street