transmission leaking fluid

If it's a 727 check the shift shaft seal. If the trans only leaks when it's SITTING that's probably it (a quart or so) since that 'level' will be exceeded when the system drains back.

My 727 leaked there, I replaced the seal, no more leaky.

You CAN do it in the car. I went through the floor to drive the new seal into place with the appropriate socket.

Napa has the seals.

hth,
Jim