The truck has 16,000 miles on it.
Last weekend I was on an up hill tight road. I was driving very easy, give it some gas then let the truck coast, still in drive, into the corners. Give it some more gas out of the corner. The let it coast again. I was not breaking hard or flooring it. Warm day.

A year ago I installed a tranny temp gauge. In that year the temp has never gone over 175. That was even when I was towing an XJ up hill with the truck loaded with camping supplies. Last weekend the temp hit 215.

Anyone know why it would get so hot when no load was on it?

I do have a larger trans cooler.

www.dodgeforum.com

The position of the trans temp sensor is my opinion.  A lack of flow of ATF will cause minor hot/cold spots.  Like near the headers or exhaust manifolds.  Or near the drum bearings in the transmission.  As long as it isn't making noise or missing shifts, I wouldn't worry about it.  

Another idea is that the pump (not the tq converter) wasn't spinning very fast at all.  The fluid wasn't moving fast enough to make use of your cooler.