Transmission leak advise

I'm looking for some advise. My Challenger has a leak. It leaves a small puddle on the RH side of the car. I got under it was wet on the pan. It does have a fresh filter fluid re-usable gasket.
Its hard to tell if it's actually coming from the pan or dipstick tube, pump seal, etc...
Is there a good way to diagnose this put it on jack stands with car running? Bad idea?
On a side note Transmission works perfect. Should I just re-seal it. Need some ideas.
BTW it's a 383 w/a 727.

Thanks, Larry