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Tranny Cooler


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Hmmm, perplexing.

It seems the preferred choice is to route through the stock radiator first and THEN the B&N. That site's explanation does make sense to me. Especially considering the temp ranges they both operate in.

Is there no concern for adding too much heat to the radiator and increasing the water temps? Or is that negligable since the radiator is so much larger and more efficient at cooling to begin with. Plus the oil coming from the trans will be cooler to begin with too. I guess that makes sense.

I think I rethunk it.

Thanks for input!

Chris

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I think the water temp will not be that effected. Stock radiator has a big fan which is triggered by water temp. They sell aftermarket tranny coolers with fans too, but I think that there is not enough room to fit one on the 850 without getting a little too involved.

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I would not recommend using a tranny cooler that either does not pass through the radiator based factory cooler or lacks a thermostat. Fluid that is overcooled is not good, either. You can buy a Permacool thermostat for this purpose. It definitely complicates the hose routing slightly since it is somewhat bulky and should not be hanging unsecured.

On Volvo 740T, the radiator held a small cooler through which fluid would pass before moving out in front of the radiator to a secondary cooler, from which it would return to the trans. The trans pump was deemed by the factory to be able to handle this extra circuit. I don't know much about 850/70 trans pumps, but would assume they can handle the extra circuit just as well.

Consider that the radiator based factory cooler benefits from the radiator fan, but the secondary cooler benefits either less -- if it is in front of the radiator -- or not at all if it is located elsewhere. You can still get high fluid temps in low airflow conditions, unless you add a mini fan to the secondary cooler, something that is often done for severe conditions.

Philip Bradley

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You cannot really over cool ATF. Well not without something like a water cooled system or some form of gas under pressure. As for too much strain on the pump, I have never heard of that. Any good cooler will have almost no pressure increase. The B&M unit is like 15mm ID, and the stock lines are 9. Oh, and you want the secondary cooler after the stock one.

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I think a certain temperature is required to burn off contaminants, just like with engine oil. If you do not route the line through the stock cooler in the radiator or through a thermostat, the trans fluid may run too cool to burn off contaminants. It depends on your driving. If you drive enough when you drive, the fluid should eventually get sufficiently hot to burn off contaminants, but this may not be the case if you do a lot of short distance driving. I don't know how often or for how long the trans fluid must reach hot temperatures of around 180 F in order to burn off contaminants and prevent damage? One a week for 10 minutes? Once per drive? Never if you have an extra trans filter (more than a screen)? Never because a trans is different from an engine and does not suffer the same problems as engine oil?

Philip Bradley

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I think the idea of having some kind of thermostat is cool, that way only when it gets above a certain temp will the cooler be in use. as part of this mod you could also get a tranny temp gauge, hopefully before hand and then reap the benefits of all your hard work

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Yes, but its built onto the radiator. So its actually heats the ATF to 180 instead of cooling it in some cases.

so what if you get a 160 degree thermostat, will that help cool it if it is hot ?

and why does the lower thermostat set off a CEL, has anyone had a CEL with their thermostat ? why does it set off a CEL ?

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Ahhhh. Ok first the lower thermostat setting off the CEL is because your running cooler. When the car is cold it runs rich. Run rich for too long you not only loose power but you get the CEL. As for the ATF, the stock system has no thermostat. Some systems to use a thermostat, but its to cool the heated fluid and maintain a reserve of cool fluid. These systems are used a lot in heavy equipment. ATF does not have to reach any specific tempature to work correctly, as long as it can flow freely.

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Shouldn't be any contaiminents in your ATF system, it is more sealed than the oil system, thus no need to burn them off.

I've seen this topic debated to death all over the internet. But in the end the lower the temp the better, it's actually that simple in this case. No matter what you do (within reason) your ATF is still gonna get pretty hot.

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  • 2 months later...

OK, I'm hoping to bring this topic back to light. But I have a simple question. Anybody with a stock 850 bumber (No R) have a tranny cooler? I'm pretty sure it'll hang lower right that the bumber right? And there seemed to be 2 sides to the whole discussion, but I'll just listen to Charles in saying that it IS a good buy.

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