2002 2500, 5.2 w/ 80K miles.
So I was waiting in line at the emissions station on a 100 degree afternoon and after about a half an hr. the coolant temps started to climb up to 230 Degrees. When they finally tested my van(it passed)and I got back on the road, the temps came back down to normal. But the tranny was slipping, especially to 2nd. to 3rd. shift. After about a half an hr., everything seems to be back to normal.
I am assuming the trans fluid got really hot, which changed the viscosity, which changed the shifting performance.
Does this sound about right and the tranny is ok?

 

I'm no expert but if idling and getting hot you might check your fan clutch.
before start up check for wobble (front to rear, waterpump) then also spin the fan, if it spins freely like more than 1/2 a full turn you may want to replace it.
Will wait for other guys to advise regarding transmission stuff, I'd only say, if it hasn't been serviced in a long time that you can recall then it is probably a good time to have a fluid and filter change.

 

Yes and yes.