Mishimoto MMTC-SP-13N 13-Row Stacked Plate Transmission Cooler Kit

Heat is what kills automatic transmissions. Hold the fluid above roughly 220 degrees for any length of time and the ATF starts to oxidize, lubrication falls off, and clutches, seals, and bearings pay for it. An auxiliary cooler is the cheapest insurance you can add, and a stacked-plate core like this Mishimoto MMTC-SP-13N moves a lot more heat than the tube-and-fin coolers most people bolt up. The 13-row plate core measures 22.85 x 7.10 x 1.25 inches and is rated to 40,000 GVW, so it has the capacity for trucks, tow rigs, and hard-driven builds where the factory cooler in the radiator tank runs out of margin.

The stacked-plate design routes fluid through wide internal passages, which is what gives it strong heat rejection with low pressure drop, so you are not choking flow to the transmission to get the cooling. Owners running it on GM trucks with the 4L80E and 6L80 report 20 to 30 degree drops on the gauge in the same driving they measured before. On a light vehicle or a CVT it will pull temps down aggressively enough that a thermal bypass is worth adding for cold-climate winter driving.

It comes as a complete kit, not just the core: 50 inches of SAE J1532 transmission cooler hose with spiral polyester reinforcement, 3/4-16 male to 3/8 hose barb adapter fittings with integrated O-rings for a leak-free connection, 3/8 hose barb unions, stainless steel worm-gear clamps, an abrasion sleeve, and four universal mounting brackets with hardware. Plumb it inline on the cooler return line, mount it in front of the condenser or radiator where it gets airflow, and top off the fluid to account for the extra volume in the cooler and lines. It works with ATF, power steering fluid, and engine oil. Ships from the USA.