Transmission oil coolers are vital to keeping transmission fluid from overheating.
Automatic transmission fluid's life span is greatly dependent on the temperature it operates at, so keeping it cool is vital to the life span of both the fluid and transmission.
Oil to Water Coolers
Most factory-fitted coolers are built into the outlet side of the radiator, which are considered oil-to-water coolers. This layout is compact, inexpensive, and has the added benefit of warming the fluid as soon as the engine gets up to operating temperature.
Oil to Air Coolers
The more common and generally less expensive type of oil cooler passes oil through a metal tube with heat sink fins like a radiator.
Add-On Coolers
Additional cooling is typically added to vehicles with a towing package, experience severe service like excessively hot regions, and in high performance applications.
Installing an Add-On Cooler
An add-on cooler should be added so that the fluid flows through the oil-to-air cooler before it reaches the oil-to-water cooler in the radiator. This prevents the fluid from getting cooled down too much, which can affect shifting.
Due to the additional length of travel the fluid will flow through an additional cooler, the owner should note that when fluid is changed, there will be a slight increase in capacity, depending on the size of the cooler, the length of the hose leading to it, and the inside diameter of both.