hey
When you install the sensor in the line pressure tap you?re putting it into a dead ended fluid tap. It will only read the temp of the transmission case.
When you tap into the out going (cooler) line (as Rick has suggested) your getting the true temp right out of the converter, This is as hot as it gets.
When you tap into the return line (lube) this tells you how cool your fluid is after the cooler has done its work. You see this lube oil is directed into the trans. and sent directly to the gear train to cool the planets, and then fall into the pan, to be sucked up into the filter and starts over again.
When you check the fluid in the pan your getting what is called running temperature of the transmission. This is a perfect place for the transmission information when you?re running stock.
However when your running a Hi stall wouldn?t you want to know how hot it is getting? This is where we recommend putting the sender unit, as this is where you can see how hot your getting coming off a run. I hope this helps ?Dave