In 95 I had an after market tranny cooler put on my 94 Dodge Ram it ran me $150. It made quite a difference when hauling a 3500lb camper. I sold the truck to my boss, it's still in service and runs just a nice as the day I bought it new.
Both my 97 & 99 Ram trucks have factory installed tranny & oil coolers which work even better, but now I am only hauling a boat or motorcycles which does not compare to the weight of the camper but average driving or even better, sitting in traffic is much cooler with the coolers. LOL
Go for it, it certainly can't hurt if you are doing any long hauling.
Cass