I´m not a tranny expert. But if it was mine, I´d drain the fluid, remove the pan and take a look and see what comes out (collect it in a clean bucket). Check the filter screens for obstruction. Clean everything, spotless, before reinstalling, dirt and grit are the enemy with the auto tranny.
I´ve had some slippage on my older XJ´s from time to time. New oil, always seemed to help. Need to change twice, a week or so apart, to get most of the old stuff out. The converter always has some oil left in there (quit a bit actually). I usually change my tranny fluid once a year (sometimes twice), Dexron is fairly cheap, have found slippage, to be more noticeable with ATF. Dexron seems to slip less.
Mine usually started slipping first, in low gear. What gear was yours slipping in? I´ve never done it, but it is said, the low reverse band has an adjustment.
When mine started slipping (usually when cold), I´d make a point of starting easy and down shifting into third in the mountains. And avoided pulling my trailer, in the mountains.
Overheating the tranny can´t be good for it, but hopefully, you did little damage. Your discription, sure sounded like low fluid. Have to check the tranny fluid, with the motor running to get a proper level. I usually shift through the gears once, then test with the motor running. Fill a little below full, to allow some room for expansion, when the tranny gets hot.
Have found restricted cooler lines, on some other makes of vehicle (not yet on the jeep). Blowing through the lines, will tell you quick if it´s stopped up or restricted. After the fluid stops coming out, there shoud be little restriction in the cooler and lines.
If you´ve doen any kind of intake work recently, the TV cable (kickdown cable), could be out of adjsutment, this cable also controls pump pressures somewhat.
Burnt oil
Low oil
Wrong oil
Plugged pickup (filter)
Plugged cooler lines
Lock up?
TV cable adjustment
Fair wear and tear (tranny getting old).