If there has been one killer of transmissions, guilty of gearbox murder more than all other causes combined, it is definitely heat. The best ways to fight transmission heat are to lessen the load on the tranny and to add more cooling capacity. Since we're not lowering the gear ratio or lightening the truck up at all, we wanted to add some more cooling capacity to the 4L80E in this Chevy 2500 4x4. The truck was at OC Tranny getting its 80,000-mile-old transmission rebuilt, and we took the opportunity to add a bigger and better Derale Hyper Cool cooler in place of the factory auxiliary cooler that comes with the tow packages on most fullsize trucks.
We chose a Hyper Cool unit because we like the electric fan option that we can wire whatever way we choose to. Since the tranny temperatures in this truck didn't ever spike unless towing heavy loads or playing off-road, we chose to wire up the fan directly to an on/off switch to use it only when needed.