Automatic Transmission Oil Coolers

Motor vehicle engineers design powertrain components to operate within a specific temperature range, with the goal of providing the optimal combination of performance and durability. The engine has a dedicated cooling system to maintain engine temperature, and in addition to its primary lubrication duties, the engine oil also cools internal engine parts, but the automatic transmission fluid does even more. It provides the hydraulic pressure that enables the transmission to function, lubricates internal transmission parts, and cools the unit so it operates properly and reliably. The ideal transmission fluid temperature for peak performance and long transmission life is approximately 175°F (79°C), and even a minor temperature elevation can result in significantly reduced service life. Therefore, to prevent transmission failure and expensive repairs, it makes sense to keep your automatic transmission cooling system in good shape and we have the components you need to do it, including coolers, lines, hoses, fittings, thermostats and more.

Vehicle operating conditions like towing a trailer, hauling heavy loads, driving in stop-and-go traffic, driving in hot weather, and driving in mountainous terrain with steep grades, can all put a strain on an automatic transmission and raise the fluid operating temperature. If the temperature rises because of a faulty transmission cooling system, the fluid can break down and lose its protective properties and leave deposits that hinder transmission operation and cause internal component failure. As the temperature increases it can result in varnish forming at about 240°F (116°C), then if it continues to rise and reaches 260°F (127°C) seals can harden resulting in leaks. At about 295°F (146°C) the fluid deteriorates to the point that clutches begin to slip and at 315°F (157°C) clutches burn out. Sustained operation with fluid temperatures of 300°F (149°C) or more will quickly result in complete transmission failure.

During transmission operation the transmission fluid absorbs the heat from internal transmission components and then dissipates it through the transmission cooler. At one time just about all transmission coolers were incorporated in the engine cooling radiator. Lines connected between the transmission and transmission cooler portion of the radiator convey hot fluid from the transmission to the cooler, where the heat is transferred to the engine coolant, and back to the transmission. While this transmission cooling system is still widely used, today many manufacturers use a separate transmission cooler that may be a dedicated standalone cooler but can also be supplemental and plumbed into the fluid return line from the radiator. This cooler is typically a liquid-to-air heat exchanger that functions like the vehicle radiator. Hot fluid flows through tubes or plates in the heat exchanger where it is transferred to fins which dissipate it to the surrounding air. This cooler is usually positioned for optimum air flow exposure behind the grille, in front of the radiator and A/C condenser.

The most common type of transmission cooling system failure is a leak. Fluid lines can become abraded, punctured or otherwise damaged, and fittings and connections can develop leaks, especially those where O-rings and seals have become hardened. Rubber hoses can deteriorate from age and heat. The heat exchanger itself can also be punctured by rocks and other airborne debris. It can also leak because of corrosion caused by exposure to the elements and road salt. However, even if the cooler isn’t punctured its heat exchanging capabilities can still be compromised if an impact has caused damaged to the cooling fins. Bent fins will restrict airflow, and they are usually too fragile to straighten.

Some performance vehicles have an additional external cooler, but the radiator is insufficient by itself and even an external cooler may not be large enough. Transmissions are very expensive to repair or replace, and if you race, you no doubt have a lot of additional money invested in your box. A performance transmission cooler is comparatively inexpensive, so it’s cheap insurance. We offer several types of performance transmission coolers in sizes to suit every application. Tube and fin coolers have serpentine tubes through which the fluid flows, attached to fins that transfer heat to the air. They’re generally inexpensive and we offer models with turbulators to increase the cooler’s efficiency. Plate and fin coolers are formed like radiators, with fluid flowing through plates attached to cooling fins. Their larger surface area makes them more efficient. Stacked plate coolers are the most efficient, with larger plates than plate and fin coolers and turbulators for increased cooling.