rear end or transmission problem?

on a very sharp and fast turn about 45 mph and just as sharp as im willing to push it at the moment somthing is causing my engine to rev like crazy. its like i just through it in neutral. it happens when in drive and in second.

i have a 904 and open 8 3/4 with green bearings and dr diff axles the center section if fairly worn ( didnt want to rebuild it as its temporary).

could the problem be the transmission or the rear?