B&M tranny cooler questions

[piecesparts]

Jeez guys, you're overthinking it... Don't try to make this a heat transfer homework problem. Lots of guys here have a tranny temp display and can watch the tranny temps. Both the 768 and 764 show good tranny temperatures pretty much year round (the specifics are out there). You can try to solve the theoretical problem all you want, but you already have the data, so what's the point? The musings about air vs liquid and whether 14400 is enough, or if it's really 14400 and is that enough are meaningless if they don't agree with the data that is already out there.

And BTW, Viper is incorrect, lots of vehicle came from the factory with liquid to air tranny cooling systems. It's been done for many many many years. Routing the tranny coolant to the radiator can give you the added functionality of warming the tranny fluid, but that is not really going to happen unless you leave it idling long enough for the engine to warm up past the thermostat's trigger temp, warm the radiator then finally start warming the tranny fluid.

And as far as cooling, you can say all you want about transfer efficiency of liquid to liquid systems, but they will only reject heat to a body that is colder than they are, meaning when your engine is running at the standard 191C, then your tranny is only going to be able to reject heat to 191C. Most all the guys running the 768 (smaller) cooler in bypass report well under 191C for the running temp on their tranny. And mine doesn't really get below 120-140C even in the winter on the highway when the cooling it as it's best.

If your radiator was just replaced, then don't bother with a tranny cooler unless you are towing alot or off roading alot. And don't compare a consumer vehicle engine to a nuclear power plant cooling system, they are COMPLETELY different. The principle is the same, but you can't draw any conclusions about what is the best vehicle radiator based on what is used in nuclear power plants.

I will agree with you on a lot of your input. Are you sure that your system is running at 191C? That would make it Celsius not Fahrenheit and that is a really high number (191C=375.8F). The fact that a cooler will only work if there is a temp difference, is true. The most efficient heat transfer is from a liquid to a liquid, due to the fact that the transfer mechanisms are more controllable. The transfer of heat from your tranny oil will never ever get to the same temperature as the medium that is absorbing it, there has to be a delta T involved. So if your radiator is holding water at 160 degrees Fahrenheit, then the tranny oil will always be greater than that temp (approximately 16 degrees temp difference on fluid coolers, at best). That is a fact of life. Transfer of heat from the oil to the air is dependent on how much air is moving and what temp it is outside. The temp difference for this type of transfer will be slightly greater than from a liquid to a liquid, more like 25 to 28 degrees delta T). That is also a fact of life, or so my A/C&R training has told me. As for comparing it to a nuclear plant, the fundamentals are the same and that is an absolute of heat transfer and fluid flow.

I am not challenging the issue of a fluid to air or a fluid to fluid cooler, what I wanted to know is if the people on this site have had issues with the fluid to air ONLY in daily use. It would seem that one would be hurting themselves with a change if they don't achieve success with their efforts. I don't want to experience the Strawberry shake and the way my life goes it could happen anytime, that is just how it goes. However, I am in wonder about the bypass that the B&M cooler says that it has for a cold liquid, because that means there is a bypass for the warmer liquid also, which to me removes the efficiency of the cooler from the get-go. There is no T/stat on that cooler that would change to let the oil flow change as it heats up. The other part of the question is aligned to the fact that if you go larger, does that hurt performance of the tranny in the winter?

Good discussion on this subject, though.