http://www.bmracing.com/PRODUCTS/Univ ... at-29-200-BTU-11x11x1-1-2

Found a good deal on this. What you guys think? Beneficial to stock transmission or no? Could always save it if I ever upgraded I suppose....Just a thought...Its by B&M.

Factory transmission coolers are marginal at best. A good cooler will greatly extend transmission life. Excessive heat is their worst enemy. I add additional cooling to any AT equipped vehicle I own, stock or modified.

If you are running a stock transmission with stock torque converter under average driving conditions I think it’s a waste of money that could be spent elsewhere. However, I agree that heat is your transmission enemy, but many others here have experimented with this and discussed it before and if you have the money and want the added protection it won't hurt.

Some will tell you to run the fluid it through it as a standalone cooler, but Pete K has recommended to me personally to run mine in line with the factory cooler.

What's wrong with running it through the cold side of the radiator?

Remember, the thermostat is on the radiator inlet side. I don't know what the outlet side is, but it's probably 40F colder.

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Isn't that the stock location? That is what Pete meant.
My trans is plumbed into the radiator on the right side, which is the factory location on my car..

Our Jeep has a tranny cooler. I have no idea if it helps, but it sure can't hurt.

Well maybe it can.

The debate on air vs. radiator tank cooler is whether or not getting the ATF too cold can hurt anything.

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From what I understand, cold ATF will affect performance and shift points but it won't hurt anything. Obviously extreme cold should not be considered cold ATF for this discussion.

However, over heated ATF is very bad...somewhere above 200 maybe is where it gets dangerous? Anyone know that?

What's you're definition of extreme cold?

If someone takes their Corvette for a drive on a 30F night, the radiator coolant is going to start out at 30F. The thermostat will start cracking open relatively soon to circulate some coolant through the radiator to raise the temperature by some amount.

The air cooled ATF cooler will always be getting 30F air.

So I'm not quite sure what will cool the ATF more, and how cold it would get, and how cold is too cold.

The viscosity of the fluid is picked for a reason, and running colder fluid for longer periods of time goes against that.

According to Bowtie Overdrives:

The fluid temperature control system is designed to properly manage the transmissions operating temperature. Most people don’t realize that routing the lines from the transmission through the radiator is designed to bring the transmission up to its proper operating temperature and then maintain it at that temperature. This is the reason that the factory’s transmission hard lines always run to a heat exchanger located in the vehicles thermostatically controlled radiator system. We have yet to see an “auxiliary” type cooler mounted anywhere that was capable of doing this job properly. Contrary to popular belief, a good transmission temperature control system ran through a heat exchanger located in the exit tank of the vehicles radiator, will normally hold the transmissions fluid temperature 30 to 50 degrees F lower than the engines indicated operating temperature. The transmission temperature will be very stable with a system like this unless; the radiator is bad, or the transmissions heat exchanger located in the radiator is ineffective. The transmission fluid flow rate through the heat exchanger should be checked. We use a simple procedure to determine if a system has any flow restrictions. Restricted flow has the same result as inadequate cooling or inadequate lubrication to the transmissions hard parts. It is our strong opinion that the effectiveness of the transmission fluid temperature control system cannot be determined without the use of a temperature guage!


With a balanced cooling system and a temperature sensor located in the pan you should indicate a normal operating temperature of less than 150 F. Most installations don’t even require additional coolers if the radiator system is well designed. When you plan to tow, you should try to over kill this requirement. If you must error while designing a cooling system for your transmission, please do so on the safe side of the equation, on the side of supplying a little more cooling than is needed, rather than not quite enough. If your system runs higher hotter than 150 degrees F you can bet the cooling system isn’t adequate or the torque converter is not locking up! Continuous operation at 150 degrees or less will insure the fluid lasts the full year between complete fluid flushes.

The number one cause of failure with these transmissions is continuously running the transmission fluid hotter than it is designed to tolerate or frying the fluid during a single catastrophic incident.


They go on to say for towing an auxiliary cooler should be installed, but in series with the radiator cooler. And that it should be bypassed in the wintertime in cold climates.

I hooked mine up so the fluid goes through the auxiliary cooler first, then through the stock cooler in the radiator. I was afraid on really cold days if it went through the stock one first then through the auxiliary that the fluid would be too cold when it gets back to the trans. Maybe it doesn't matter so long as the stock one is still being used but to keep the voices in my head happy, I made sure the fluid went through the stock cooler last before returning to the trans.

They say that IF you have an aux cooler, that the ideal way to set it up for the winter, but in the summer they say the opposite.

I don't know how the hell that could be piped to switch based on temperature...



Seems to me the way to go with an aux cooler would be to put it after the radiator tank and put a thermostatic bypass on it. This would maintain the most steadily cool temperature year around, without being overcooled in the winter.