IMHO if your radiator is all aluminum, there should not be a need to bypass the trans cooler. I replaced my radiator when a leak started. Exterior; did not affect the trans. The stock radiator is aluminum with untrusting plastic side oil and trans cooler cores. I replaced it with an all aluminum radiator and put an aftermarket trans cooler in series with the radiator trans cooler at about 150000 miles. Now at 230K, I have had no issues. Replaced the water pump and thermostat at about 190000 miles. Other than that, it has been bulletproof. Of course to be on the safest side, you would cut the pipes coming and going to the trans, flare the ends, hook up high pressure oil hoses to a oil cooler at the front of the radiator. On an end note, not an engineer but the oil may need to run through the radiator not only to cool but to heat up the oil in severe cold weather.

 

I had the separate trans cooler installed today bypassing the radiator. I had the cracked radiator replaced with a new plastic one. They were able to use the original line without cutting it by removing a retainer clip. Sooo glad this is finally done. I'm ultra paranoid after it happened to my H3. Well worth the investment to not have a huge repair/mess later on.

P.S. There is another truck with this same setup. I think the Nissan pathfinder, and the metal would rust internally and cause a leak and cause the same problem destroying trans left and right, that's why I was apprehensive about just going to all metal radiator and decided to do the complete bypass

 

At 230k my heater corr plastic disconnects snapped. The plasticT coupler connecting the heater core to the water pump also turned to mud. I would suggest replacing with a brass coupler next radiator flush. These plastic parts just dont hold up. Original hoses were fine although smart to replace them. Fyi hummer maniacs