You can also install a temperature sending unit in a tee inserted in one of the lines that run to the cooler. The line running from the transmission to the cooler would show the highest temps, but it is up to you. You would want to establish a normal temp for either location and then you would know if it is running hot. Also be sure that the "Tee" does not obstruct the flow of fluid in the line. I did the pan because it is a real mess to drain the transmission without a drain plug to first drain most of the fluid. The only drawback it that some mechanic in the future may take the shortcut of not removing the pan when changing the fluid. That is really an oversight function that you need to address.
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