sheri,
I added a trans cooler to a GM product once, when they installed the transmission cooler radiator in front of the ac (cooling condensor)
it was just to much for the cooling system and the truck would get hot.
Radiator was just not big enough, not enough air flow through radiator.
the truck had the V6 gm engine, so the radiator was not as large as a v8 truck radiator.
are you sure the vehicle does not have an transmission cooler?
all I am saying is this: on a hot day pulling a loaded trailer, you need the cooling system to be in perfect working condition, its not a good feeling having to monitor your heat gauge more than your fuel gauge.
the vehicle also had the same differential gear ratio as your tow vehicle 3.42, it struggled with the load on hills. however it got good fuel mileage not towing.
I traded it for a 2500 series chevy truck v8 auto, this truck was set up for towing as it had the transmission cooler and the radiator was about 12-15 wider and had maybe 3 rows of fins, do not remember, but it never got hot. This truck also had the 3.73 ratio differential.
I would talk with some others that have towed your weight load with that truck motor/trans/differential combination and if they did fine, they you should be good to go.
