My thoughts on the radiator heating the tranny fluid - it wouldn't. Even in cold weather what do you do, start the car and drive off. How long will the car be running before the water in the block actually circulates to the radiator, probably a few miles down the road. If warming of the trans. fluid was critical, it doesn't seem like it would run and shift properly when you first took off.
My Dak FSM says if the trans. fluid is too cold, it won't shift up into overdrive unless the fluid is over 50*F.
Therefore, fluid too hot is bad and you would plumb to radiator and then cooler. Fluid too cold is -not- likely to be a concern unless you live in Alaska maybe. It seems that plumbing from the aux. cooler and back to the radiator is negating whatever you are trying to achieve, you cool it down and then warm it back up???
C
