Cars with automatic transmissions must be equipped with a transmission oil cooler because the oil in the automatic transmission may overheat. Overheating of the oil will reduce the performance of the transmission and even cause damage to the transmission. The transmission oil cooler is usually a cooling pipe placed in the water outlet chamber of the radiator. The coolant cools the transmission oil flowing through the cooling pipe. A metal pipe or rubber hose is used to connect the transmission and the cooler.