Something to look at is the color of the transmission oil. If It´s bright red (like it comes out of the bottle) your usually OK. If it´s a lighter color red, It´s somewhat used up, if its light (fadded) red with a straw color (kind of golden) mixed in, it´s used up (usually at this stage it will smell slightly burnt). If it´s a dark straw color to light brown, change it yesterday (it will smell really burnt). And don´t forget to occasionally change the filter, it does get clogged up on occasion. When I see a transmission, with used up oil. I often change the oil, run it for a week. Then change the oil and filter. The torque converter has a bunch of oil in it, that isn´t changed with the regular transmission oil, in the pan.
When towing I usually avoid 4 th gear (or fifth in a stick), except when driving down an incline. And keep the RPM´s up some, to help avoid the torque converter from locking up.
I come from cold country, so my philosiphy of transmission coolers, is a little different from, common thinking. I install the auxillery cooler, before the radiator. At minus 10 deg. the transmission works better with the oil heated some by the radiator. Besides, the aux cooler before the radiator or after, the transmission oil, still comes out of the cooler pretty darn hot, in the summer. Like the motor, the transmission is designed to run above 180 deg. closer to 200 +.
I´ve occasionally had to adjust the TV cable (kick down cable) which does have an affect, on sharp shifts and shifts point also. I´ve replaced a couple of transmission´s, where the TV cable was well out of adjustment, and was immediatly noticable. It would want to kick down at half pedal or wouldn´t kick down at all.
I installed a switch to my aux fan relay, when towing I turn it on, before things get hot. Also switch it on, when sitting in traffic on hot days. Don´t really know if it helps with the transmission, but sure cant hurt much.
I have a drain plug on my transmission pan. I change the transmission oil every spring and/or fall depending on useage.