I have a 8.25 rear, I have done the jack up and spin wheels test and they spin opposite directions. So, it appears that I have a open rear. But sometimes I get both tire to spin why is that?
it's an open rearend..........the weight on each tire will determine whether it will hook up w/both tires, sounds like your weight on each tire is pretty close to each other.
i had an open rearend in my car for years and used air shocks, each with it's own schrader valve to balance the weight on each tire, it would hook up posi all the time.
doesn't matter if the car is in neutral or park to do the tire spin thing, if it's in park, neither tire will spin if it's a suregrip..........
higgs