Is it pre or post TC? Is it the fluid that is going to the cooler, or a true internal temp?

It is located in the valvebody but I never followed the passageway to see if it was fluid being returned from the cooler or what.

It measures sump temps.

Yikes! That is not the answer I was hoping for Mike.

Fluid coming out of the converter goes strait to the trans cooler and that is the hottest fluid there is in automatic transmission. Temps can vary from 240F on a mild working torque converter to well over 350F on a hard working converter. Measuring this fluid coming out of the converter does not tell us much at all. We need to know how efficient the cooling sytem (trans cooler) is and we will only find that out by monitoring the sump temps. Fluid coming out of the trans cooler goes directly to lube spray ( lubricating planetary gears an such) before it is dumped to the sump ( pan). At this point, we need to see how hot the fluid actually is. If the fluid is too hot we need to modify something. This is where synthetic fluid shines because it is made to work way beyond the capacity of dino fluid and it keeps on living without breaking down.
mike