99 F250 Transmission overflow

[Olerugger]

Stats: 99 F250, 7.3, 4 x 4, Lariat, Auto--Overdrive, 245K miles

I just returned from a trip pulling my two horse LQ Gooseneck trailer to VA, about 6 hr pull with some mountains. When I arrived I was forced to search for a level campsite and spent some time moving to and from several sites. During the last move I noticed fluid leaking from my engine, looked like transmission fluid. Shut it down and let it cool off. Leaking stopped but I had lost close to 3 quarts by my measure. Fellow camper says I got it too hot moving around campsite and was coming out overflow in transmission. Never heard of that. Any thoughts? When I returned I had the fluid drained and filter changed by my local shop, they showed me some copper/brass? residue on the filter and inside the pan, it was a very lite film. I bought the truck some time ago and don't know when the last time the transmission was serviced. It has been a strong truck so far with no issues