transmissions are funny . I've rebuilt my share for my race car , and have learned that the cooler you keep it , the longer it lasts .

Why the factory runs the trans fluid through the radiator where it sees 220 degrees , without a external cooler in the return line .... is beyond me . Utterly stupid .

You only see this setup on a pickup truck with the " tow package "

If you can keep a transmission at 100 - 150 degrees , it will live for a very long time . At 200 degrees , the rubber seals start to harden and get brittle . After 80,000 miles of this , it starts to go downhill slowly . How it even lasts 80,000 is pretty good . Its like slow cooking a roast .

Now the funny part ..... not so funny though ..... once the fluid is burnt and black * sign of being wayyyyyy to hot * and starts shifting weird , then you change the fluid , that new fluid washes out the grime and gunk from the o-rings that are hard a brittle , and they dont seal at all now . Now your trans gets even worse because nothing is sealing , and pressure is lost .

So .... If I were you , I would start saving for a rebuild , and add a cooler After the radiator AFTER you rebuild it . Find which is the return line to the trans , and put a parallel cooler inline there . This will reduce temps tremendously .

Or .... cross your fingers and change the fluid .... sometimes you get lucky and its just starving for fluid because the filter is partially clogged .

Then add a cooler without hesitation .