I think I know what your problem is, you have a locked diff...
But seriously, they invented the differential about a billion years ago because a non-differential axel was never going to work properly in a normal car. Why do you think going back to a non-differential rear end is an "up-grade" for your road-going car? Use your brain and replace your busted diff with a normal T series diff, or if it's a track car you should use your brain and replace your busted diff with a normal T series diff.... wait, did I just say the same thing? Derrrrrr