The trans fluid can get extremely hot depending on the type of torque converter. I don't think the radiator cooler works very well to help cool as much as the length of the lines. Most heavy duty trucks have an external trans cooler for that purpose. Under load the fluid gets too hot for the radiator to help much. If you think about it almost all trailer mfgs tell you to add a cooler to avoid problems. With the engine
oil you want to get the temp up as soon as possible. BinB is right, a thermostat would be the best. It allows the
oil to heat up with the engine and then open at a given temp.
Don