Is it leaking transmission fluid into the differential? You can tell if you check the fluid level of the differential, and it's over-full; also, tyranny fluid would be correspondingly low. If so, then much more than likely you're correct in your diagnosis.
"If everything seems under control, you're simply not going fast enough" --Mario Andretti
1995 E500 street car
1986 Porsche 944 Turbo S track car