There's no greater enemy for a transmission than heat. Whether your 2003-2009 Dodge Ram 5.9L / 6.7L Cummins is a dedicated tow vehicle, hardworking fleet truck, or a daily driver, you need to ensure that your transmission runs cool. Luckily, Mishimoto has developed a direct-fit transmission cooler to do just that. Our 2003-2009 Dodge Ram 5.9L / 6.7L Cummins transmission cooler utilizes a stacked plate core for durable and powerful cooling. With a massive 212-percent greater core volume, 244-percent increase in fluid capacity, this trans cooler is a huge improvement over stock 2003-2009 Dodge Ram 5.9L / 6.7L Cummins transmission cooler. The Mishimoto transmission cooler is not only larger than the stock cooler, but more reliable too. When the stock cooler's thermostat fails, it fails closed, bypassing the cooler and returning hot fluid to the transmission. Mishimoto has solved this common issue by making the thermostat in our 2003-2009 Dodge Ram Cummins transmission cooler fully serviceable and easily bypassed for constant cooling. A port located at the top of the cooler provides easy access to the thermostat for servicing in just a few minutes. Replacement thermostats can be purchased individually if needed