Hayden 698 Tube-and-Fin Transmission Oil Cooler

The Hayden 698 is a tube-and-fin auxiliary transmission oil cooler for any vehicle running hot automatic fluid, which is most trucks, SUVs, and tow rigs after a few years. It mounts in front of the radiator or A/C condenser and plumbs inline on the cooler return line, either in series after the factory radiator cooler or as a standalone. The core measures roughly 11 by 5-3/4 by 3/4 inches and comes with 3/8 inch barbed inlet and outlet fittings, so it takes standard 3/8 inch cooler hose and worm clamps.

What separates this one from a bare tube-and-fin core is the internal thermal bypass. When the fluid is cold on a winter start, the bypass routes flow around the fins so the transmission comes up to temperature normally instead of pumping thick, cold fluid through a giant heat sink. Once the fluid warms, full flow goes through the cooler. That is why it works in cold climates without the shudder and slow warm-up you get from a plain add-on cooler.

Heat is what kills automatics. Every 20 degrees of extra fluid temperature roughly halves fluid life, and towing, heavy loads, or stop-and-go traffic push temps well past what the factory radiator cooler can hold. Owners installing this on Tacomas, 4Runners, Silverados, Foresters, and half-ton trucks report the trans temp gauge sitting noticeably lower on grades and long tows. Note it ships as the cooler and hose barbs; you supply hose and clamps, and a separate Hayden mounting bracket kit if you are not tapping existing holes. Ships from the USA.