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

Heat is what kills automatic transmissions. Fluid that runs hot loses its film strength, and once the clutches and seals start cooking you are on the clock for a rebuild. This Mishimoto MMTC-SP-13N adds an auxiliary cooler to the transmission line so fluid comes back to the pan in the range it is supposed to live in. Owners routinely report a 20 to 45 degree drop after installing it, especially on trucks that tow or run in hot climates.

The core is a 13-row stacked-plate design measuring 22.85" x 7.10" x 1.25". Stacked plate flows better than a cheap tube-and-fin cooler and holds a lower pressure drop, so you are not choking the line to gain cooling. It carries a 40,000 GVW rating, which is why it holds up on 3/4-ton and 1-ton trucks, RVs on the V10, and 4L60E, 4L80E, 6L80, and TH400 builds that see real load. Because it is universal it also works as a power steering or engine oil cooler.

Install is straightforward. You cut into the cooler line, route the fluid through the cooler, and clamp it down. The kit comes with 50 inches of SAE J1532 transmission cooler hose with spiral polyester reinforcement, 3/4"-16 to 3/8" hose barb adapter fittings with integrated O-rings for a leak-free seal, 3/8" hose barb unions, stainless-steel worm-gear clamps, an abrasion sleeve, and four universal mounting brackets with hardware. Note the supplied hose is a short run, so a long line routing may need extra J1532 hose, and a thermal bypass is worth adding in cold-winter climates so the fluid still reaches operating temperature.