Ive got a transmission cooler much more beefy and jesus-like then your transmission cooler and if I drive down the highway for 20 minutes with no TCC lockup my **** gets pretty hot... hot, like, 215+ degrees when it would normally be 165-175 max with 100+ degree ambient temps.
Of course, the weather here makes your forearms sweat almost year round but the fact still remains that turning off TCC in every gear (including fourth) will reduce efficiency (aka gas mileage) and build up more heat. I have TCC in third disabled though since I never cruise in that gear and I think on all 3800 PCMs it is disabled by default in all of 1st and 2nd gear.
