How a trans cooler works.. The hot fluid comes out of the trans and goes into the trans cooler inlet goes thru the cooler and comes out the outlet..(Well you all knew that) It then goes into the cool slide tank of the radiator.. At this time if the fluid is still hotter than the engine coolant in is cooled down some.. If it has cooled down to much coming out of the trans cooler, it will be heated up by the hotter engine coolant. As you can see that trans fluid tank inside of the cool side of the radiator either cools the fluid if needed or heats it up if needed.... Back in the old days many of motor homes would run hot at times.. Running a thermostat controlled engine oil cooler would help keep engine coolant temps down. Which would help keep the cool side of the radiator down helping the engine and the trans. Ed