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By-pass Trans Cooler


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I've seen many threads on here discussing the need to not over-cool the 5EAT and incorporating a by-pass valve when adding an external trans cooler.


Yesterday a NAPA rep stopped by my work and dropped off a flyer and inside was an ad for Hayden's new line trans coolers with a built in by-pass valve.




Looks pretty promising for a DD application and certainly simplifies the installation. I'm not a fan of the fact that their literature just states "optimum temperature" with no mention of opening and full flow temps. I sent an e-mail asking for more information but have not heard back from them yet.


Just thought I'd throw this out here as soon as possible in case some are looking for options and don't want to mess with the added mess of a by-pass valve. If anyone has any connections at Hayden, I'd love to get more info on the functioning temps...something tells me that they won't be responding since my question wasn't the usual "what part for my car".





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This is the first time I've seen that they've added the technology. I know I am not on the cutting edge on tech but seems new enough to me. Hayden got back to me today and I am surprised that it would over cool the trans. Their response:


"Thank you for contacting Hayden.




Our By-Pass cooler gate closes at around 180°F (Depending on Fluid weight) to allow fluid to travel throughout the cooler.


As far as “holding at ideal temperature” that is around 190°F. If you live in Northern states with very cold winters, you can run into “overcooling” with a normal non bypass cooler which can damage the transmission. Our cooler is designed to open the gate if it sees temperature below 170°F to allow the fluid to go through the bypass channel until fluid temperature rises again."


Keeping the trans above 170 doesn't seem like "overcooling" to me but maybe that is just me. Since Mrs. Spif's car is just a daily I think I'll be leaving the trans lines alone.

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Mine was around 140-150f in the winter time on the highway. The fluid viscosity based bypass doesn't work very well with our high end synthetic transmission fluid (look up the specks on the OEM stuff, it's better then AmsOil!).


The BEST transcooler would be an OEM JDM/EDM one, it uses engine coolant in a large fluid-fluid heat exchanger. I have one on hand that I plan on putting in-line with the Hayden + 165f thermostat I have now.

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