Travel Trailer in my Future

I would also plan on adding a trans temp gauge so you can see what's going on and when the trans is getting hot. By the time the light comes on the fluid is already toast. The 6L80 in the newer Tahoes and 5.3 vehicles is pretty sturdy and should be fine for towing 6K lbs. The tow package usually gets you a bigger radiator which means a bigger trans cooler inside the radiator as well.

I've never run hotter than 200 degrees on the dash gauge with the stock cooler even towing in 100 ambient temps, but then again Phoenix is a different ball game in the summer.