Help leaky tranny

My kids 74 swinger /6 has a tranny leak.. (sometimes) I'm not sure which trans it has, but i was under it the other day wiped it down and ran the car didn't see any leaks. Just tonight I moved it in front of the garage while I was tinkering with stuff. It was parked there for about an hour, not running. He went out in it and after he left there was a spot of trans fluid about the size of a dinner plate where it was parked. But this only happens sometimes. I'm kind of dumbfounded (maybe I'm just dumb) I looked around where the dipstick tube goes in when I was under it, seemed alright. The dip stick itself seems a little wierd how it fits in, the cap on the top dosen't really seem to fit/go down into the top of the tube. He has it pretty jacked up in the back right now so that his tires won't rub, and it was on a little incline with the front down when it was parked in front of garage. My thought was maybe fluid moving downhill to the front and overflowing/maybe coming out dipstick tube. But sometimes it does it when it's parked on a flat area, but not always. Anybody have any ideas? I'll be back under it again tomorrow for another look see. Thanks :banghead::-k BTW have only had the car a few weeks so no long history