Trailer question

BCB is correct its the brake lockout, i have it on my 99 P3 trailer as well.

Also make sure you are NOT in overdrive. That slows down the speed of the input shaft, which drives the oil pump, which slows cooling down. Even on level ground it can cause overheating in the middle of the Summer.When you say it happens when backing up the driveway, I would assume that is AFTER a significant drive towing? If not, sounds like either a gauge or temp sensor problem as it isnt going to get hot just cranking up cold and just backing up the driveway.2008 Pantera Classic2014 Mercury Pro XS 200

Your transmission fluid should have two cooling devices. First runs the fluid through the bottom of the radiator to let the engine coolant extract some of the heat, then it should run to a usual heat-exchanger type device mounted in front of the radiator. If you dont have this second oil cooler, you can buy em at advance/auto zone. Pretty easy install. It is amazing how quickly heat will completely destroy the lubricating properties of transmission fluid, so this needs addressing quickly. As the oil molecule chains shear, lubrication gets worse, and a new transmission will follow if you are not careful. First step is to make sure you have that secondary transmission oil cooler in front of the radiator, and that it is not blocked with bugs, grass and crud.2008 Pantera Classic2014 Mercury Pro XS 200