AW4 necessary BTUs to cool

Anyone know how many BTUs of cooling is required/recommended for the Jeep AW4 automatic transmission? Thinking of running AW4 fluid through B&M 13,000 BTU and OEM tranny cooler. Removing lines from radiator.

I can't answer for the exact BTU cooling requirement. The real question is how much cooling does the relatively small exchanger inside the radiator provide? It is liquid-liquid so more efficient, but also warm coolant. I would guess its getting maybe 10k BTU cooling at most once everything is warmed up. Maybe a single larger air cooler would be better and simpler.

Looks like you are in a warmer climate, so I don't think warm up is an issue. In cold climates, keeping the in-radiator exchanger helps get the tranny warmed up and shifting better earlier.

Thought about it some more and the math part of my brain kicked in.

Powertrain losses can be as high as 20% under normal circumstances (probably lower for a locked t/c). Lets assume all of that is occurring in the tranny and needs to be dissipated as heat. 30 HP crusing power for a lifted XJ at highway speed seems reasonable. At 2545 BTU/Hr per HP, that's about 15,000 BTU/hour.

Of course all bets are off for rock crawling or mudding. Lots of t/c slipping and excessive use of the skinny pedal could really add up. Maybe requiring upwards of 60k BTU/hr of heat removal required.


Also keep in mind that 13k BTU/hr rating is highly dependant on the airflow. YOu probably won't get that while rockcrawling.

All very good points. The BTU of a tranny cooler must be an average, or BEST CONDITIONS measurement.

As you may have surmised I am thinking of pulling my tranny lines off of my radiator and running them through a cooler. Currently I have it going through the radiator, the OEM tranny cooler and a B&M 13k BTU cooler.

With temps around 100 here I am seeing the Jeep run hot. It runs hotter on the highway than on the local streets. It has been suggested to me I remove the heat that the transmission creates from the equation. Of course that also means I'll be removing some of the heat sink (the transmission) as well.

Thanks for the information!

What upgrades have you already done to the cooling system?

3 core CSF radiator
Hessco high flow therm housing
Hessco high flow thermistat (180 degree)
Grand Cherokee Heavy Duty fan clutch (yesterday)

Replaced OEM
heater hoses
upper and lower radiator hoses
water pump
fan clutch (replaced it yestday)

Everything but the heater core.

I'm thinking about changing the water pump tomorrow.