[Big Dave]

My old 6.2 truck had a tranny cooler about a third the size of the radiator.

All my tranny disasters came when the truck was cruising down the superslab.

In a way, locked-TC is the worst condition. The TC (with no relative motion between rotor and stator) is pumping zero fluid through the cooler. I understand newer automatics transmissions have an auxiliary fluid cooler pump.

Nothing cruises the slab like a stick.

The 700R4 is notorious for "hunting." In and out of TC lockup.