Sorry if this is a dumb question, but have you ever tried changing to a cooler thermostat to keep the engine/tranny/etc cooler? I put a 180 t-stat in mine.

I live in South Florida. I had a tranny cooler installed when I started towing a motorcycle trailer. AAMCO installed it inline with the OEM tranny cooler so that they both work together.

The fluid still looks bright pink and fresh since the last tranny fluid change at 60k miles. (Got 100k now).