AEM Transmission Temperature Gauge AEM 30-4402 If you own a truck and tow with it, one of the most overlooked things is a temperature gauge for the transmission oil. If you aren't careful, you can cook the transmission in one trip if you run it too hot.  Even run it "too close" several times you may end up killing the tranny after a couple trips. So do yourself a favor and keep on top on things with an AEM Trans Temp gauge.