Mine would fail at fluid temps above 175...which isn’t hot at all, considering normal coolant temperature on an LQ1 is a little above 200 or so.
HOW do you know that the fluid temp was 175?
WHERE is the sensor? In the pan, or in the cooler circuit?
they used to teach us in the gm classrooms that the cooler is actually a heater for the trans in the winter time as the coolant in the radiator heats up much more quickly that a transmission does
There are multiple ways to connect add-on trans coolers.
In a cool-to-cold climate, the add-on cooler would get the transmission fluid first, with the in-radiator cooler between the add-on cooler and the return port in the transmission. This allows the in-rad "cooler" to warm the fluid as needed in cold weather.
I have been looking into a repair valve for this condition on my transmission it rides in a different portion of the bore that is not as badly worn. Sonax makes several kits
Which valve are we talking about?
Part number for this Sonax "Kit"?
I am aware that Sonax makes a heaping pile of repair parts for automatic transmissions. They seem to be a-reputable company with clever "fixes" for OEM trans-design failures.