Derale 13316 6-Pass Tube & Fin Transmission Cooler -6AN

This is Derale's 13316 auxiliary fluid cooler, a 6-pass tube-and-fin core sized 13.5 x 7.625 x 0.75 in that plumbs inline on the transmission cooler return line to knock temperature out of the ATF before it goes back into the pan. The core is 1/2 in copper tubing expanded into aluminum cooling fins, with embossed turbulators pressed into each tube to churn the fluid as it passes so more of it touches the tube wall and gives up its heat. It carries -6AN male inlet and outlet fittings and a black powder-coat finish.

Heat is what kills automatic transmission fluid. Once ATF lives much above 240 F it starts to oxidize and varnish, and the industry rule of thumb is that every 20 degrees over that roughly halves fluid life and cooks clutch material. Trucks that tow, haul, or sit in stop-and-go traffic build that heat fast, and the factory cooler in the radiator tank often is not enough on its own. Adding this cooler downstream of the factory cooler drops the return temperature and buys the fluid and clutches a much longer life.

It is a universal mount, so it fits most automatics and works as an add-on ahead of the pan return. Plumb it into the return line (the one feeding fluid back to the transmission), mount it in clean airflow ahead of the A/C condenser or radiator, and secure it with a through-core mounting kit or nylon zip mounts. The -6AN ports let you run braided AN line or adapt to 3/8 in hose barb. At 1.65 lb the core is light enough to hang from the fittings and brackets without a heavy frame.