Yes I'm hard on transmissions. Especially if first gear is really tall like the th400. Tallest ever on market. Load one down in my case 15-20k gcw, try to go up a 15-20% grade, stop and go traffic all day long, even with 4.10 gears in pumpkins. Thing get overheated really fast, stalling out was not uncommon. Yes I did have an aftermarket big cooler. Helped a little. I have more get up and go with my 6 sp auto, 3.42 gears and a V6 in my current 1500 than I did with the 88/89 BB 3500's I had. I would've had to drop to at least a 4.88 to not have as many issues as I did.
Driving on a freeway is different than here in Puget sound local roads. Saw an article the other day, steepestroadin Seattle proper is 26.3%. Those grades wreck havoc with an improperly speed drive train.
Marty