727 leak @ tailshaft when on jack stands?

Guys,
I have a 360/300 magnum crate backed by a year old rebuilt 727. Funny thing is it leaks tranny fluid out the tailshaft housing @ the driveshaft when the front end is on jackstands for a signifigant length of time. I first noticed it when I left it up overnight for brake work and found a puddle under the tranny. I'd love it if you guys could make me smart on this. :coffee2: