Mishimoto Transmission Cooler Stacked-Plate Core

2003–2009 Dodge Ram 2500 / Ram 3500 5.9L & 6.7L Cummins

Part #: MMTC-RAM-03SL

Overview

The Mishimoto Transmission Cooler is a purpose-built cooling solution designed specifically for the 2003–2009 Dodge Ram 2500 and Ram 3500 trucks equipped with 5.9L and 6.7L Cummins engines. This direct-fit cooler addresses the critical need to manage transmission temperatures, especially under heavy towing, hauling, or high-performance driving conditions. By maintaining optimal transmission fluid temperatures, it helps extend the life of your transmission and enhances overall drivetrain reliability.

Featuring a stacked-plate core design, this cooler significantly outperforms the factory unit by increasing core volume and fluid capacity, resulting in superior heat dissipation. Whether you’re towing heavy trailers, operating in demanding fleet environments, or pushing your Ram to its limits, the Mishimoto transmission cooler delivers dependable, efficient cooling to protect your investment.

Key Features

Engineered for durability and ease of maintenance, the Mishimoto transmission cooler offers several advanced features that elevate it above the stock cooler:

• Direct-fit design for seamless installation on 2003–2009 Dodge Ram 2500 and 3500 5.9L/6.7L Cummins models
• Stacked-plate core construction providing robust and efficient heat transfer
• 212% increase in core volume compared to the OEM cooler for enhanced cooling capacity
• 244% increase in fluid capacity to maintain lower transmission temperatures under load
• Fully serviceable thermostat with a convenient top-mounted access port for quick maintenance
• Thermostat bypass option with included stainless-steel plug for constant cooling in hot climates
• CNC-machined stainless steel hose barb fittings replace corrosion-prone quick-disconnect fittings
• Includes transmission cooler hose for direct connection to stock soft-lines, eliminating common failure points
• Improved reliability by eliminating weak points found in OEM coolers

Construction & Design

The Mishimoto transmission cooler is constructed from premium materials designed to endure the rigors of heavy-duty use. Its stacked-plate core maximizes surface area for efficient heat exchange while maintaining a compact footprint that fits perfectly within the factory mounting locations. The cooler’s rugged construction resists corrosion and physical damage, ensuring long-lasting durability even in harsh environments.

High-quality CNC-machined stainless steel fittings replace the factory’s quick-disconnect fittings, which are prone to corrosion and seizing. These fittings provide a secure, leak-free connection to your truck’s transmission lines, enhancing reliability and simplifying maintenance.

Additionally, the cooler features a thoughtfully engineered thermostat system that is fully serviceable and easily accessible through a top-mounted port. Unlike stock coolers that fail closed and bypass cooling, Mishimoto’s design allows for quick replacement or bypassing to adapt to varying climate conditions without replacing the entire unit.

Installation & Fitment

Installation is straightforward thanks to the cooler’s direct-fit design tailored specifically for the 2003–2009 Dodge Ram 2500 and 3500 with 5.9L or 6.7L Cummins engines. The kit includes all necessary hardware, CNC-machined hose barb fittings, and a transmission cooler hose that connects directly to your truck’s existing soft-lines. This eliminates the need to remove or replace stubborn OEM 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, providing a hassle-free installation experience for both professional installers and DIY enthusiasts.

What's Included

• 1 x Mishimoto Transmission Cooler (stacked-plate core)
• Fully serviceable thermostat installed with 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 2500 and 3500 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.