Does Your Truck Need a Transmission Cooler Upgrade?

trans cooler
Transmission cooler mounted in front of the truck's radiator. photo by Matt Wright, 2014

 Back in the old days -- way back in the old days -- there was only one part of your truck's drivetrain that you needed to keep cool, the radiator. Even that was simple. Fill it up with some loose mixture of antifreeze and water, make sure the radiator cap was on nice and tight, check your fan belt for tightness and wear. Nice and simple. Today's trucks are far more complicated and advanced than your father's carbureted hauler.


One of the many advances most trucks have seen is the addition of a transmission cooler. No, this isn't an ice pack that you stick underneath the truck to keep things cool. For those of you who are less familiar with the anatomy of a heavy duty automatic transmission, let me give you a quick run-down. Your transmission is full of fluid -- called transmission fluid. This fluid is part of a complex hydraulic system that transfers the power of your engine to the wheels. The fluid in your transmission is always moving. When you are pulling a trailer or hauling a very heavy load, the transmission fluid finds itself under a lot more pressure than it experiences during normal unloaded cruising. This pressure and velocity produce heat. Under normal circumstances this heat is dissipated through the transmission case itself. It's a great conductor of heat and can keep the system cool pretty well without any outside help.

Of course, you didn't get a truck so that you could always operate it under normal conditions, right? As you pull and tow, the metal body of the transmission can't dissipate enough heat to keep the fluid cool. The fluid can become so hot that it loses its hydraulic qualities and starts to make the transmission slip.

 The easy answer that automakers came up with was the transmission cooler. This transmission cooler takes the heated tranny fluid and runs it through a miniature radiator, just like your coolant. It's amazing how much cooling can happen with even a small transmission cooler. 

Do you need a transmission cooler? Most trucks these days come with an optional towing package. This package almost always includes a transmission cooler. But just because you're doing a little towing doesn't necessarily mean you need a transmission cooler. If you're pulling something big and heavy like a camper you may want to make the upgrade. Something small like your bass boat will pull along just fine without heating the system up any more than regular driving. If you plan to tow big, or if you plan to tow a trailer on top of loading the truck's bed to the top, you may want to consider going with a cooler. If you've already had problems with your truck's transmission overheating, the decision to get a cooler is right in front of you. 

Should you upgrade your existing cooler? If you're lucky enough to have a truck that came equipped with some type of transmission cooler, it's often very easy to upgrade to a medium-duty or heavy-duty unit.

The same criteria apply here as above. The type of towing you plan to do, what type of terrain you live near and the weather in your towing season are all factors that can affect your need for greater transmission cooling capacity. 

TIP: Some trucks that didn't come with the towing package may already have the plumbing for a transmission cooler installed, and just need the addition of the radiator section!