I'm confused on the Transmission thermostat function. I'm assuming it redirects coolant to the transmission cooler but wasn't sure at what temp it is triggered to open. Anyone have a clue?

According to RAVE the thermostatic valve is opened by transmission fluid temperature. When this reaches 80°C the valve opens to allow engine coolant through the cooler.

Phil

Thanks Phil. Apparently I missed it. So theoretically the engine thermostat mod doesn't affect the cooling of the transmission fluid.

Once above 80°C the transmission fluid will follow the engine coolant temperature. At light loads the electrically heated thermostat will allow the engine coolant to climb to over 110°C. I frequently measured transmission fluid temperatures above 100°C during normal steady-state conditions as a result of this.

If you lower the engine coolant temperature the transmission fluid temperature should come down with it.

Phil

Great! I was needing to add about 8oz of coolant every 600 miles. Just got back from the same trip at about 700 miles and no measurable coolant loss through the radiator pinhole. The pinhole itself is almost dry. I have to believe that the theory of less stress to the cooling system is more than theory. Theory tested so now I can fix the pinhole.