Trans cooling

I have always used a 2nd trans cooler w/fan manually controled, which I mounted under the bed of the truck...I spiced the cooler in the return line just before the trans.When my temp started to climb a little too high just turn on the fan an temps would drop...When towing heavy in 92* temps that cooler helps....I also have 2 temp gauges there is one for trans temp,my 2nd gauge is mounted to the trans cooler output line(made a bracket to hold the sender against the line)...as for fluid the ATF+4 is a synthetic fluid,which walmart sells