I put a Powertrax unit in a friends 66 GT350H.
Like me, he was a track addict. At first he liked it but coming out of a turn the car would hook for no reason and spin. My friend (as well as myself) thought it was the front end alignment. He tried several settings and the same result, apex/hook/spin.
I drove the car and the same thing. As soon as power was applied, the rear end would break loose and the car would hook to the inside.
Took the Powertrax out, installed a true-trac and the problem was solved.
I remember asking if he was going to sell the powertrax on eBay, "no, I don't want to be involved in someone's wreck".