The cooled fluid from the radiator dissipates the ATF heat and is then. returned to the transmission for another cycle. In a down-flow radiator, the transmission oil cooler. is located in the bottom portion of the radiator. In a cross-flow radiator, the transmission oil cooler. is located in the side of the radiator. â¢ Transmission oil cooler assemblies consist of metal tubing or an assembly of metal tubing and. rubber hose. Transmission oil cooler hose is used to absorb engine and road vibration. â¢ While ATF was designed to operate at temperatures of 175ËF, the reality is that transmission and. cooling lines are routinely subjected to conditions that cause it to operate at 220ËF or more, up to. 300ËF intermittent.