Joe,
I think I stumbled onto my problem today... Too hot ATF.
Reason? My A/C condenser in front of the tranny cooler is leaking, and has caused the A/C condenser to pick up a lot of dirt, blocking air flow.
Or that's my primary theory. I'm going to leave it for now and fix the A/C condenser first. Also going to try to hose out the dirt and see what happens.
VK