Mishimoto Transmission Cooler

2003–2007 Dodge Ram 2500/3500 5.9L Diesel, 2007–2009 Dodge Ram 2500/3500 6.7L Diesel, 2008–2009 Dodge Ram 1500 6.7L Diesel

Part #: MMTC-RAM-03SL

Overview

The Mishimoto Transmission Cooler with a stacked-plate core is a high-performance cooling solution engineered specifically for Dodge Ram 2500 and 3500 trucks from 2003 to 2009 equipped with 5.9L and 6.7L Cummins diesel engines, as well as the 2008–2009 Ram 1500 6.7L Diesel. Designed to manage transmission fluid temperatures effectively, this cooler is essential for drivers who regularly tow heavy loads, haul equipment, or operate their trucks under demanding conditions.

By maintaining optimal transmission temperatures, the Mishimoto cooler helps extend transmission life and improves drivetrain reliability. Its advanced design outperforms the factory unit by significantly increasing cooling capacity, making it an ideal upgrade for anyone seeking enhanced durability and performance from their Ram’s transmission system.

Key Features

Built to deliver superior cooling performance and reliability, the Mishimoto Transmission Cooler offers several key advantages over the OEM cooler:

• Direct-fit design tailored for 2003–2009 Dodge Ram 2500 and 3500 5.9L/6.7L Cummins models and 2008–2009 Ram 1500 6.7L Diesel for hassle-free installation
• Stacked-plate core construction that maximizes heat transfer efficiency and durability
• 212% increase in core volume compared to the factory cooler for enhanced heat dissipation
• 244% increase in fluid capacity to maintain lower transmission temperatures under heavy load
• Fully serviceable thermostat with a convenient top-mounted access port for easy maintenance
• Thermostat bypass option with included stainless-steel plug for continuous cooling in hot climates
• CNC-machined stainless steel hose barb fittings that replace corrosion-prone quick-disconnect fittings
• Includes a transmission cooler hose designed for direct connection to stock soft-lines, eliminating common failure points
• Rugged construction resists corrosion and physical damage for long-lasting durability

Construction & Design

The Mishimoto Transmission Cooler is crafted from premium materials engineered to withstand the rigors of heavy-duty use. Its stacked-plate core design maximizes surface area for efficient heat exchange while maintaining a compact size that fits perfectly within factory mounting locations. This design ensures superior cooling performance without compromising space or requiring modifications.

Durability is enhanced by corrosion-resistant materials and CNC-machined stainless steel fittings, which replace the factory’s quick-disconnect fittings known for corrosion and seizing issues. These fittings provide a secure, leak-free connection to your truck’s transmission lines, improving reliability and simplifying maintenance. The cooler’s fully serviceable thermostat system, accessible via a top-mounted port, allows for quick servicing or bypassing to adapt to different climate conditions without replacing the entire unit.

Installation & Fitment

Installation is straightforward thanks to the cooler’s direct-fit design, specifically engineered for Dodge Ram 2500 and 3500 trucks from 2003 to 2009 with 5.9L or 6.7L Cummins engines, as well as the 2008–2009 Ram 1500 6.7L Diesel. The kit includes all necessary hardware, CNC-machined hose barb fittings, and a transmission cooler hose that connects directly to the truck’s existing soft-lines. This eliminates the need to remove or replace the factory quick-disconnect fittings, reducing installation time and complexity.

Whether upgrading from the stock cooler or replacing a failing unit, this cooler fits perfectly without any modifications, making it suitable for both professional installers and DIY enthusiasts.

What's Included

• 1 x Mishimoto Transmission Cooler with stacked-plate core
• Fully serviceable thermostat installed with top-mounted access port
• Stainless steel thermostat bypass plug
• CNC-machined stainless steel hose barb fittings
• Transmission cooler hose for connection to stock soft-lines
• Installation hardware and detailed instructions

Ideal For

This transmission cooler is ideal for Dodge Ram owners who demand reliable transmission cooling under heavy loads or extreme conditions. It is perfect for:

• Towing enthusiasts regularly hauling trailers or heavy equipment
• Fleet operators requiring durable, maintenance-friendly cooling solutions
• Performance drivers pushing their trucks in high-stress environments
• Owners in both cold and hot climates, thanks to the serviceable thermostat and bypass options
• Anyone looking to upgrade from the stock cooler for improved transmission longevity and reliability

Mishimoto is a performance cooling brand offering aluminum radiators, intercoolers, oil coolers, hoses, and supporting hardware built to manage heat on hard-driven street and track vehicles. For boosted setups and towing/off-road rigs alike, Mishimoto upgrades are designed to increase cooling capacity and reliability where factory systems can become a limitation.