is there weights welded to them? I am not sure what you mean buy internal balance that usually applies to the engine. the thing is if it vibrates sitting still, its something in the moving parts while in neutral. Basically anything from the transmission tailshaft forward. The only time I had this issue it was a unbalanced pressure plate in a 4 speed setup, but Id be looking at similar areas, what about the flex plate etc? Mopar flex plates are a cross shaped peice of stamped steel but I wouldnt suspect that, Id suspect the converter because its heavy when its full of fluid.