Boiling point: How much can your diesel auto trans handle?

My 2006 Dodge had the weak link transmission. I like to drive mostly back roads where the transmission would stay in 3rd gear and not be in lock up mode. Running on “juice”. It would get very hot at times I saw 260 degrees on my Juice With Attitude monitor. Last year I bit the bullet and spent the money for a BD “built” transmission. What a world of difference! Never see above 175 degrees. Shifts beautifully. And always is in the right gear. Nice