I guess I need to explain in a little more detail, I used the bottom of my custom aluminum 32 Ford radiator which was plumbed from the transmission, then I plumbed the cylindrical finned cooler (it was 22" long and had 2" fins around the entire circumference) between the trans and radiator. So, I only had the bottom of the radiator and the auxiliary (22"L finned cooler) plumbed to the trans.
Captainmack, good results with the cooler with regard to the change in trans temps. 150 is excellent. You are running through the radiator then to the cooler. The next experiment, run the aux cooler only and see how the trans temp changes. I know, too much work but it would be interesting.
Olerodder, got it! does anyone have trans temp numbers when running just the aux cooler and no radiator cooler? I ask because fluid transfers heat better than air.
my current trans never gets above 150, I just run an aux. cooler not using the radiator provided one. when I redo my lines this winter while engine is out I will plum in my radiator. Also pretty sure all of the GM truck radiators have the trans cooler on the side not the bottom of the radiator, (they use one side for oil other for trans fluid). If I remember right optimum trans temp for dex VI fluid that gm uses in their transmissions is 185, and their engines run at about 220 degree's.... that being said engine warms up waaaay faster in a normal car than the transmission unless your racing with it...so I still believe that radiator assists in getting transmission up to temperature. In modern car it matters, because most people do not want to feel their shifts....
Zoomzoom, I wouldn't be surprised if on initial startup that was happening. I think GM radiators are cross-flow correct? That may explain why the cooler is in the side? Question, why plumb in the radiator when you are running 150 with just the aux cooler? Less plumbing with the just one cooler (cleaner looking) and a bit cheaper as I'm using -6AN braided line and fittings.
Wow that would really complete the experiment... So much conjecture on the topic. Real world experience is so valuable(actual temperature readings, not just "I never had any problems" ) I went with PaulS 's advice...he is a master transmision expert. As far as GM and new cars and trucks, their running temps are soooooo irrelevant to our cars. their drive train is different. It amazes me that they run so hot..220 degrees. I guess it makes them more efficient and more thouroughly burn gas and emmisions..