Thought I would share the cheap-ass idea for an ATF temp gauge that I just installed. I picked up a digital oven thermometer, removed the metal "probe" housing around the thermocouple, cut it down and sealed it up with some heat-shrink and installed it in my truck. I routed the line through the rubber boot for the gear selector, and up over the transmission, and attached the probe to the output hard line for the stock cooler. It is held on and insulated with a piece of split heater hose and a hose clamp. The display unit is sitting under my parking brake lever. The thermometer has an audible alarm for when the temp exceeds your setting, a range of 0 - 250C (32 - 480F) and I tested it as accurate to 1 degree at freezing and boiling. It runs off of a single AAA battery I don't know how long it will hold up in this service, but I wanted something that would allow me to compare before and after some transmission mods that are coming, so if it gives up the ghost in a couple of months, I won't mind. So far after one city drive, temps seem to stay in the 50-60C (120-140F) range once warmed up. For comparison, the stock ATF temp light comes on at 150C, and off at 120C (300F and 250F). At those temps you are already compromising the fluid and likely the transmission. Some pics: The thermometer, the thermocouple, the modified temp probe.