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Automatic transmissions and hydraulic systems depend on pressurized oil to perform optimally. During operation, a tremendous amount of heat is generated in the process. Automatic Transmission Fluid (ATF) and hydraulic oil are not only used to transmit power. They are also vital to cool, lubricate and help seal internal transmission and hydraulic components.  

Compared to hydraulic oil, ATF is a more superior (and expensive) product. This is because as it was formulated to work at higher and wider temperatures ranges. It does so to maintain its viscosity over these ranges and absorb and hold water in saturation, thus preventing corrosion. 

A high quality hydraulic oil or transmission oil cooler will help you solve this issue by significantly extending the life of your hydraulic or transmission oils. 

This is because hydraulic oils or transmission oils operating at temperatures above 65°C (150°F) will start to deteriorate at an accelerated rate, and thus result in shorter oil change periods. 

In this guide, you will learn all about what a transmission oil cooler does, the purpose of having one and where you can get the hydraulic or transmission oil cooler that suits your needs.

What is a transmission oil cooler?

First things first, what is a transmission oil cooler and what does it do? 

Basically, machines and automatic transmissions generate more heat when required to operate outside the parameters that they were originally designed for. 

Transmission or hydraulic oil fan cooler

For example:

  • An internal combustion engine modified to produce more power.
  • A transmission required to transfer more torque and power like when carrying a heavy load or towing a trailer. 
  • Racing applications or extended high duty cycles where high power is applied for extended periods of time.
  • A machine designed for operation and use in Northern Europe or North America but sent to operate in hot humid and or tropical environments.

In these scenarios, a hydraulic oil or transmission oil cooler is a great way to keep your transmission from overheating, thereby giving your oil a longer lifespan which in turn maintains correct performance and prolongs the life and the reliability of the critical transmission and hydraulic components and parts in your machinery. 

In Short, Oil coolers help you get the Best performance from your equipment for Longer.

A transmission or oil coolers function by cooling down the fluid heated by the transmission, an engine or even a power steering pump. 

The Cooling effect is created by slowing down the oil flow and greatly increasing the surface area of the pipework that the oil is traveling in.

This larger surface area is what cools the fluid, which is then routed back to the transmission, engine or power steering pump in a continuous loop. 

Some transmission oil coolers such as this one even come with a temperature switch (or thermostat) so that the cooler does not run during colder seasons or when the oil is cold.

What happens when a transmission or hydraulic oil cooler goes out or stops working effectively?

When there is power transfer, friction or a resistance to oil flow, this generates pressure as well as heat. The temperature of an oil in a circuit will continue to increase until the added thermal energy has the same value as the combined radiation and convection energy absorbed by the surrounding atmosphere. After a certain operating time the oil temperature rise will eventually slow and then stabilize.

If this stabilized oil temperature is too high, the oil must be cooled because hot oil will cost you in repairs, a lost job, or a lost race!

Here are some examples of things that will happen when a transmission oil cooler goes out:

1. Shorter Oil Life

Hydraulic oils or transmission oils operating at temperatures above 65°C (150°F) will start to deteriorate at an accelerated rate, this will result in shorter oil change periods. For example, having to change your hydraulic system’s oil every 1000 hours instead of 1500 hours, or your transmission oil every 15,000 KM instead of 30,000 KM. This will then result in more money spent on oil and filters, which can cost you quite a lot over time.

2. Internal and external leaks

Internal leaks reduce efficiencies, power and or torque of hydraulic cylinders, pumps and motors and in the case of a transmission may cause erratic performance, slow acceleration and or gear shifting.

External leaks can make a mess of your mobile equipment as leaks are blown all over the underside of your vehicle, dust and grime will then stick to the oily components creating an ugly sticky mess requiring cleaning.

3. Dangerous Slip Hazards

Oil leaking or dripping onto a non absorbent floor or road not only makes a mess but also creates a potentially dangerous slip hazard that may result in an automotive accident with personal and property damage and possible prosecution.

4. Mechanical Damage

Large external leaks if left unchecked will reduce or deplete the oil level of the hydraulic oil circuit causing excess friction and even more heat generation, poor performance, and eventually catastrophic mechanical damage.

5. Poor Efficiency

Lastly, the hydraulic system’s efficiency is reduced because the oil viscosity changes (usually gets thinner) and more power losses are experienced resulting with even more heat being generated with reduced machine performance and or productivity.

If on the hand you operate a piece of equipment at UNDER the oil’s designed temperature range you risk the following problems.

6. Insufficient Lubrication

When a pump cavitates, it is not actually pumping as much oil volume as it was designed to do. Therefore not enough oil will reach critical mechanical components to produce drive, support loads, reduce friction and or carry heat away. The result is accelerated mechanical wear and or damage.

7. Temperature Control and Design

As with internal combustion engines that have water cooling and thermostats that control temperature to a relatively narrow range, thermostat control is also available for oil cooler systems to provide quick warm up and cooling down, as well as preventing over cooling.

Where can I buy a transmission oil cooler?

Now that you understand the disadvantages of running your machines or hydraulic equipment without an oil cooler, you might want to purchase one as soon as possible.

At, we have various oil coolers available for purchase according to your needs. 

For 240 Volt, 20-30 LPM:

Small flow transmission oil cooler

Small Flow Cooler 20-30 Lt / min 3/4″ Bspp 12V/ 24V / 240V fan

For smaller concrete trucks:

Smaller concrete trucks transmission oil cooler

AUSTRIAN MADE OIL COOLER DC 12V / 24V With 12 Litre Oil Tank

For heavy duty oil coolers:

However, it is important to have the following information and details before you proceed. 

  • m = Weight or mass of the oil in reservoir [kg] 
  • c = specific heat capacity [Wh/kg°C] (for hydraulic oil this is c ~ 0.53 and for water it is c ~ 1.16 )
  • t1 = oil temperature at the begin [in °C]
  • t2 = oil temperature at the end [in °C]
  • T = heat up time [hours]

Also desirable are the following:

  • Pump or System Oil flow in Liters / minute = L/min
  • Altitude above sea level (at machine’s location) = in m
  • Desired oil temperature at inlet = in °C
  • Maximum expected cooling air inlet temperature = in°C

Please see the full explanation on how to find the required oil cooling requirement here

For design assistance and sizing, please contact us by email at or phone us on +61 (07) 2102 0026.