too cool... no, i have dual trans coolers, one has a 10" electric fan on it and the other is the larger of the two common B&M coolers, the 70264. i run them in series. i added the second one because for me the B&M could not keep up with my demands. i do not tow that often, but will on occation. what i do is wheel my truck and use it for search and rescue -that means lots of long climbs in the mountians in hot days in the middle of summer(and in the cold of winter too). sometimes its slow going under 20mph and that load will really put a strain on things, as there is no real "air flow" to speak of under 20mph especially in 90* heat. i have a trans temp gauge that i installed before the cooler so it reads the hottest possible temps. with one cooler installed and no passengers in my truck but some recovery and search gear (no trailer or anything else like that) i pegged my gauge(reads up to 250*) on a long climb on a forest service road getting to the staging area.
i had pegged the gauge 3 times that first summer actually, the first time was in over 100* heat in traffic for over two hours, i actually had to pull into a drive through car was and went through twice to cool the truck down, that actually helped a lot. then the second time was stated above. and the third time was at the end of that summer when i went down to lassen national forest(northern Ca.) for a week long wheeling/camping trip, it was another climb on a forest service road, but this time i was loaded down with another passenger, my dog, tools, food, spare parts ect. i tipped the scaled at over 6400lbs on my way down. it didnt take long for me to heat things up, so i said enough was enough and bought the second cooler. installed it and have never had an issue sense. around town i see temps around 150-180 depending on the time of year, and on the hwy its 130-150 depending on the time of the year. even when out 4wheeling in the snow i can see temps over 200 when pushing snow or breaking trail ect. the fan is on a thermo switch that it will kick on at 180* and not shut off till the temp drops down to 160, and i have had that fan kick on several times while out wheeling, even in the winter time with snow. i dont think you should be worried about too cold. if its too cold you wont shift into over drive and the trans will hold shifts until the fluid warms up.
