Trans fluid temp

[junkyardjeff]

Got a Ford C-4 hot enough to slightly burn the fluid and loose third,found out it had debris between the cooler and radiator so I changed the fluid and installed a bigger cooler(no cooler in radiator) and moved it away from the radiator.   Came home from a show about 140 miles from the house and put the infared thermometer on the cooler and it was about 140 degrees so what I need to know is just how hot does the fluid have to be to cause damage and is 140 cool enough.

[Rochie]

Well if the trans was cooled by the cooler in the rad it would run at, probably 180*

[jaybee]

Here's a source that says optimal is around 175, 240 is too hot.  https://mechanicbase.com/transmission/normal-operating-temperature-for-an-automatic-transmission/