Towing

[sleeve]

There is not much of a difference between the cooling performance of the tow package or non-tow package KJ's. The only change is really the mechanical fan. That extra fan is the only component that aids cooling of the vehicle components. The tow package didn't include any enhancements to the transmission cooler BTU [heat rejection] ratings nor did it increase the BTU rating for the radiator. So the only real improvement is that mechanical fan + Electric Fan combo. [why is it there? keep reading...]

Below is my reasoning [just my opinion really]
Very low speed means no air moving over the trans cooler / radiator surfaces. Little to no airflow means that the there is no media to help pull heat out of the system. This leads to a build up of heat in the transmission cooler. Since the radiator heat is what kicks on the electric fan - there could be a situation were minimal to no airflow over the transmission cooler is present. [Cold KJ, First Tow...] This is why Chrysler added the mechanical fan - to always ensure that there would a constant flow of air at low speeds.

Situations were this would apply: i.e. Manuvering a trailer into/out of a boat launch. Or when you are having trouble getting a trailer straigthend out. Both of these situations present a chance that the transmission cooler might not have adequate airflow to transfer the heat from the cooler into the ambient air. [Heat always goes from hot surface to cold]


All of this is overcome by simply turning the A/C on in the KJ to kick on the electric fan 100% and you won't have low air flow anymore.

 

[trail rated]

I think that the 45RFE models came with aux. transmission coolers if it came equiped with the tow package, not sure though but I will check.

Also, even though the electric fan pulls more air than the KJ style mechanical fan at idle, when the engine is at higher engine RPMs the mechanical fan pulls more air than the electric fan. When towing, the engine will be operating at higher RPM. Of course, I don't know at what temperature the KJ mechanical fan clutch fully engages but if it's like the WJ than it should engage at 230* so it probably doesn't do anything until the engine reaches that temp. If that is the case and you do a lot of towing than it probably would be a good idea to get a new fan clutch, aftermarket clutches start engaging at 175* and fully engage at around 190* (it senses heat from the radiator so it won't start to engage until the thermostat opens).

The computer turns on the electric fan based on the inputs from sensors that measure engine coolant temperature, battery temperature, transmission temperature, and IIRC power steering fluid temperature.

 

[sleeve]

My 45RFE / Towpackage KJ does not have any extra transmission cooler. Just the in-radiator unit.