You cold just pay SLOWERADO $5 bucks a week to stay under my truck and blow on the tranny. I think any of them would be fine as long as you get a bigger one. NAPA has one cheap for RV and about every parts house does as well. Just depends on what name brand you want

 

Which one seems to produce the coolest transmission temps? Can too low of a temp hurt the tranny? If so, what's the limit? Thanks for everyone's input.

 

I have a Hayden too. If it is too cold that is bad as the fluid will never get warm...think cold motor. A decent sized cooler around 14" x 7" is plenty large for light towing and speeding around.

Temps around 100*-150* are pretty normal, and what I would shoot for.