727 leak

Possibly leaking from the reverse lever shaft, a bad o-ring. Oil will leak from the end of the shaft, down the case onto the case/pan gasket , and then flow around the entire gasket perimeter and then drip from the lowest point of the gasket, which depends on what angle the car is parked. Quick fix without tearing things apart, is to drain the fluid to below the shaft, push the shaft in as far as it will go, degrease the shaft end, the bore, and case, seal (pack it) with some rtv, gray or, let it cure, refill and you may have ended your leak.