Transmission Cooler for 2003-2009 Cummins

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  • Regular price $502.95
Free shipping on orders over $150.


  • Fits all 2003–2009 Dodge Ram 5.9L & 6.7L Cummins*
  • 212% increase in core volume
  • 244% increase in fluid capacity
  • Includes fully serviceable thermostat for fast warm-up in cold climates and thermostat bypass for constant cooling in hot climates
  • Stacked-plate design for tough and reliable cooling
  • Eliminates corrosion-prone quick-disconnect fittings
  • Available -8ORB to -8AN adapters allow the use of AN transmission fluid lines. (2 required)
  • Patent #D912701
  • Mishimoto Lifetime Warranty


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 with a liking for the dragstrip, 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% greater core volume and 244% increase in fluid capacity, this trans cooler is a huge improvement over the 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; no more replacing the entire cooler if the thermostat fails. Owners in cold climates can still enjoy the fast warmup times that the thermostat provides, while owners in hot climates can choose to bypass the thermostat by replacing it with the supplied stainless steel bypass plug.

To make this cooler even easier to install and service, Mishimoto saves you the hassle of removing seized fittings. The provided CNC-machined, stainless steel hose barb fittings let you cut to the chase, literally. These fittings and the supplied transmission cooler hose allow you to remove the quick-disconnect fittings and connect the stock soft-line to the Mishimoto cooler.

Like all Mishimoto products, this transmission cooler is backed up by our Lifetime Warranty with Accident Protection for worry-free cooling as long as you own it.


(1) Mishimoto Stacked-Plate Transmission Cooler
(2) High-Pressure Transmission Cooler Lines
(1) Removable Thermostat
(1) Removable Thermostat Bypass
(2) CNC-Machined Stainless Steel Barbed Fittings
(2) CNC-Machined Aluminum 3/4"-16 ORB to Hose Barb Fittings
(6) Worm Gear Clamps
Mishimoto Lifetime Warranty


Patent #D912701

* This kit requires cutting of the stock transmission cooler lines to remove the quick-disconnect fittings. Mishimoto provides CNC-machined stainless steel hose barb fittings to splice the supplied transmission cooler line with the stock soft-lines. Please see installation instructions for more details.