Don't run the transmission cooler lines through the radiator. Bypass that and just use an external cooler. No sense heating the transmission fluid to engine temp.
That is somewhat true, but it is less frequent than most people believe. The bottom of the radiator is the coolest part. With a 180* thermostat and a 10* temp drop, it's 170 around the cooler. The temperature of the transmission fluid entering the cooler is higher that that.
