Transmission Guardian is a small color changing LED that you can mount on your dash to give you a visual indication of your transmission temperature. The LED turns on at 135° and changes colors as your transmission temperature rises. Please refer to the chart as to what each color indicator means. Transmission Guardian was designed with transmissions in mind but it can be used on engines, differentials or any source that can use our temp sensor. Transmission Guardian can be used as a direct replacement for temp gauges or can be used in conjunction with.