Auto Meter 4357 Electric Transmission Temp Gauge, 2-1/16 in

The Auto Meter 4357 is a 2-1/16 in electric transmission temperature gauge from the Ultra-Lite line, reading 100 to 250 degrees F on a silver dial with a red pointer. It uses Auto Meter's air-core electric movement, so the only thing running to the dash is a signal wire — hot ATF stays in the transmission instead of being routed through the firewall the way an old mechanical capillary gauge does.

The kit ships with the 1/8 in NPT temperature sender plus 3/8 in and 1/2 in NPT adapters, so the sender threads into a factory test port, a pan bung, or a cooler line fitting without hunting for extra parts. Most techs put the sender in the pan or on the cooler return line for an average sump reading; putting it in the line ahead of the cooler will read hotter because that fluid is coming straight off the converter. Wiring is straightforward: ignition-switched 12V, ground, sender signal, and the included bulb and socket assembly for the dial light, with red and green bulb covers in the box if you want the dash colors to match. The gauge runs on both 12 and 16 volt systems, so it works in a street truck or a race car with a 16V battery.

Heat is what kills an automatic. Fluid life falls off sharply once sump temperature climbs past about 240 F, and a converter under load can push pan temperature there quickly on a long grade with a trailer behind you. A dedicated trans temp gauge tells you when to drop out of overdrive, when the auxiliary cooler is doing its job, and when to shut down and let it cool before you cook the frictions. Auto Meter part number 4357, built in Sycamore, Illinois.