I drive a 96 well maintained Explorer with the above trans. I have a drain plug and do 30K trans oci, 170k miles. The truck didn't come with a trans cooler.

I drive in the mountains up some very steep grades. Sometimes the truck is GVWR loaded, driven at a lower speed. With 4.10s things can really rev up. I monitored temperature, it was going into the 210-220s sometimes.

I bought a the largest Hayden cooler, which seems a bit larger than the stock one they use on the the explorers. The 679. I also bought new lines that accommodate a cooler, they were cheap and the old ones were quite rusty. Ford and the aftermarket make sets.

Now my temperature gets to 179 on warmer days under load. However, it will never drop below 160 on the highway, even if it is colder out and unloaded. A trans shop in the middle of nowhere where I asked for an opinion said there is an internal thermostat, and you don't want be under that. He said the cooler will probably buy you a few years, If you can keep it under 180 the servo seals and gaskets will live out their maximum life. He also said the 679 (or Derale version) goes on every rebuild. He showed me about 50 of them in the corner. He went out to see how I mounted it on the ex, he said it is a tight fit.

Problem is I wanted it cooler. Is there a way to remove that thermostat?

 

Ive always been told that running under 165 is as bad as running over 200. With 170-180 being the sweet spot, but im by no means an expert. The trans in my pickup hits 240 until i backout if im towing anything (ZF5)