Transmission coolers help to remove heat from the transmission fluid. The transmission is lubricated the component involves in the car’s transmission. So how does the transmission cooler work? Transmission fluid gets heated by the transmission, engine, or the power steering pump moves to your vehicle’s radiator and then to the transmission cooler. Cold air flowing over the fins of the radiator cooler carries away the heat and lowers the temperature of the transmission fluid. The cooled transmission fluid proceeds back to the transmission, and the cycle repeats itself.
Adding a transmission cooler helps to reduce strain on the engine and other transmission parts to ensure they work efficiently, reduce wear and tear and prolong their lifespan. All cars have some type of transmission cooler that helps prevent the transmission from overheating. However, some vehicles may require an auxiliary transmission cooler for additional cooling. This article will teach you everything you need to know about adding an auxiliary transmission cooler to your car.
Should I Add a Transmission Cooler?
Adding a transmission cooler to your car will significantly lower the temperature of the transmission fluid and prolong the life of the car’s transmission and engine. An overheating transmission is one of the most common problems that can cause car failure when ignored. The ideal temperature range for transmission should be 175 to 220 degrees Fahrenheit. Every 20 degrees above the optimum range will decrease your transmission fluid, burn it and reduce the transmission lifespan significantly. Adding a transmission cooler will cause a net average decrease of 20-25 degrees in temperature.
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All vehicles made after 1975 have in-built transmission coolers in their radiators as standard equipment. Most cars can do without an exterior cooler. However, sometimes there may be a need to add a secondary aftermarket transmission cooler to increase the cooling effect of the transmission.
Some circumstances overwork your engine and transmission. The heat they produce increases significantly, which means the existing radiator cooler may not handle the increased cooling demand of the fluid and transmission. So, here are some of the circumstances that will require you to add an aftermarket transmission cooler:
- If your transmission has overheated or overheats frequently, you might have to consider installing a secondary cooler or having the original repaired or upgraded. An overheating transmission will damage other parts of your car and lead to frequent repairs.
- If your vehicle is leaking burnt transmission fluid, it is a sign of a problem. Usually, healthy transmission fluid is bright red or pink; the old fluid is deep brown or red, while burnt fluid is typically dark brown with a burning smell—burned fluid results from a failing cooler, low or old fluid that needs replacing.
- If you have a truck you typically use for towing a heavy load, you will need a more robust cooler or an extra one to match the added strain on the engine and transmission from the load.
- If you stay in a place with hot weather, external heat raises the resting temperature of the fluid. The optimum range of temperature for transmission fluid is about 175 to 220 degrees Fahrenheit, and if it exceeds this temperature range, it will start to burn and break down. Adding a cooler will be able to maintain the optimum temperature of the fluid.
- You should add a transmission cooler to your off-roading vehicle. The vibration and extreme terrain strains the car, and cooling an off-road vehicle will require more than just a radiator cooler.
How Much Does it Cost to Add a Transmission Cooler?
The cost of a transmission cooler depends on the type and size your vehicle demands. A small-capacity cooler for an everyday vehicle will cost between $30-$80. It will cost you between $150 and $250 to install a heavy-duty transmission cooler for a towing or drag racing vehicle. This cost will include labor and other additional accessories like adapters and tubes. Most auxiliary coolers come in a complete installation kit which consists of mounting accessories and tubes. If you are knowledgeable about cars, you can easily cut down the labor cost by installing the cooler yourself.
Does a Transmission Cooler Increase Towing Capacity?
A transmission cooler will not increase your vehicle’s towing capacity. However, it increases the cooling efficiency of your transmission fluid. Your transmission is overworking during towing and producing a lot of heat, hence why you may require an additional cooler to help maintain the transmission fluid at low temperatures. Low fluid temperatures will allow your vehicle’s transmission to handle its towing capacity properly.
What Size Transmission Cooler Do I Need?
When looking for a transmission cooler for a towing vehicle, it should have the appropriate GVW rating for your car; the higher the rating, the higher the cooling capacity. The Gross Vehicle Weight Rating is the safest maximum weight your vehicle is designed to handle, including the curb weight(weight of your car when empty), passengers, accessories, fuel, tow load, and trailer.
Below is a chart showing the GVW rating of a towing truck and its appropriate cooler size.
| Vehicle | Vehicle Towing Capacity | Recommended GVW rating of transmission cooler |
| Small compact cars | No towing | 10,000 – 16,000 lbs |
| Pickup trucks and SUVs | Towing up to 7,500 lbs | 22,000 – 26,000 lbs |
| Mid-size car | Light towing | 14,000 – 18,000 lbs |
| Heavy-duty trucks and motor homes | Towing up to 10,000 lbs | 22,000 – 30,000 lbs |
| Mid-size trucks and full-size cars | Towing up to 5,000 lbs | 18,000 – 24,000 lbs |
| Super duty trucks and large motor homes | Towing up to 13,200 lbs. | 28,000 lbs and above |
Can I Run Two Transmission Coolers Together?
Yes. Your vehicle can run with two transmission coolers installed, especially if there is a need for an extra cooling effect for the transmission fluid. If you live in a warm area bypassing the radiator with a larger external cooler is better. When you join the auxiliary cooler to the radiator in a series, the radiator ends up reheating the fluid before returning to the transmission.
If you live in a cooler climate, we recommend keeping the radiator transmission cooler to work with the external cooler. The radiator will heat the fluid enough to optimum temperature. You can over-cool your transmission, which may not be able to flow as easily as warmer fluid, making your transmission slow.
When installing a secondary cooler, it is crucial to consider the mounting location and how the transmission lines run. You will have to route the new transmission lines from the radiator to the external cooler. The flow of fluid should be like: Hot transmission fluid > Radiator cooler in > Radiator cool out > External cooler in > External cooler out > Cool fluid into the transmission.
How to install a transmission cooler
Follow the step by step by below to install an auxiliary transmission cooler properly.
Things you’ll need
- Plies
- Screwdriver
- Hand drill and a selection of drill bits
- Razor knife
- Hacksaw or small pipe cutter
- Drain pan
Directions
- Cut your hoses slightly longer than the rough estimate.
- Find the metal tubes that connect the transmission on one end to the radiator on the other end.
- Place the auxiliary cooler so that its inlet and outlet lines face the lines from the radiator cooler.
- Mount the auxiliary cooler 1/2 inch to one inch in front of the radiator or the A/C for cars with air conditioning.
- Use the mounting hardware provided in the transmission cooler kit to secure the cooler in place to prevent it from coming into contact with moving parts.
- Place a catch pan under the radiator.
- Use an open-end wrench to disconnect one of the lines that enter the radiator from the transmission, usually the top one.
- Have someone crank the engine for a few seconds and ensure the engine does not start. The transmission fluid should flow from either the radiator or from the disconnected line. If the fluid flows from the radiator, that is the outlet. Install the hose connector adapter provided in the cooler kit to the outlet neck of the radiator.
- Connect the rubber hose to either of the outlets on the auxiliary cooler by slipping it over the connection point. Route the other end of the rubber hose to the adapter on the radiator, mark the required length of the hose and cut accordingly.
- Slip that open end of the hose over the adapter fitting on the radiator and secure it with a hose clamp. Tighten the hose clamps at about 15 to 20 inch-pounds of torque. It does not come loose from car vibrations.
- Repeat the same hose fitting process for the second hose that runs from the auxiliary cooler to the transmission.
- Check for leaks and loose connections during the first week after installation.
Can You Over Cool A Transmission?
Heat is a common cause for transmission failure, but so are severely low temperatures. Manufacturers have designed transmissions to work at a specific temperature range. In sub-freezing weather conditions of about 20 to 30 degrees Fahrenheit, the transmission fluid will gel up, and the transmission will run slowly due to lack of lubrication.
The transmission has to run cool enough not to burn the transmission fluid but also hot enough to remove any condensation that builds up inside and maintains the fluid’s suitable viscosity for the best operation. Here are some of the effects of over-cooling your transmission.
- Viscous fluid. The transmission fluid becomes more viscous and thicker in the cold. The fluid will not lubricate the transmission parts, which will wear down parts quicker. You can fix this by using synthetic transmission fluid that is less dense in cold temperatures; it also prevents oxidation and the breakdown of the gears.
- Shifting problems. A freezing transmission will shift harder and cause delayed shifting on moving parts. Hard shifting will increase pressure on these points and cause unnecessary failure.
- Contraction. Transmission parts will contract and cause faster wear from increased friction and leaks because the seals shrink and harden.
- Delayed overdrive. Since computers control transmissions which also give it adaption capabilities. When the transmission is frozen, the computer will cause a delayed overdrive until the transmission heats up to optimum temperatures. This delay will make driving uncomfortable and increases the pressure of forwarding gears.
- Condensation. Water in the transmission forms when the temperatures drop too low and cause the moisture in the air to form into water droplets. If the temperatures drop below 32 degrees Fahrenheit, these water droplets turn to ice, expands, and cause cracks in the transmission casing and valve body. You cannot repair these cracks; the whole transmission has to be replaced by a new one.
In these freezing weather conditions, connecting an aftermarket transmission cooler to your radiator has been shown to help with overcooling. The already cool fluid will leave the transmission and first pass through the auxiliary cooler, dropping a few degrees. It will then flow into the radiator cooler, where it will warm up to its operating temperature before going back to the transmission.
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Final Thoughts
The best way to ensure your transmission does not overheat is to install a higher-capacity transmission cooler than the standard. Transmission coolers are not just helpful in towing but even for vehicles in high traffic daily situations. It will not only cool your fluid temperatures but also increase the longevity of your transmission.