[FatfreeGTO]

^^ I disagree, what happens when you are sitting in traffic and your engine is starting to overheat. If you plumb into the radiator first and then the external cooler now your trans fluid temps are closer to where they belong. If it goes through the radiator last you've simply re-heated the fluid to your coolant temp.

Modern external coolers self regulate based on the how thick the fluid is, colder fluid being thicker, less fluid goes through thus limiting the "over cooling" of the liquid.