What is the Automatic Transmission Torque Converter, and How Does it Work?

Today on the Sun Transmission blog we will tell you what the torque converter is, how it works, its components, benefits and maintenance. Stay and read to learn more about this mechanism.

What is a Torque Converter?

The vehicle engine produces a type of rotational energy called torque, which is sent to the wheels by the transmission. This requires the torque converter system, a component that acts much like the clutch in a manual transmission.

The torque converter is a system with a mechanism similar to that of the hydraulic clutch: it connects the engine's torque transmission to the automatic transmission, adapting the output torque to allow the engine to turn over when idling and transmitting the torque when accelerating.

How Does a Torque Converter Work?

This mechanism is a kind of metal doughnut filled with transmission fluid or ATF, which inside has a pair of turbine fans facing each other to transfer power through a fluid coupling.

One of these fans called impeller rotates by means of a shaft that is connected to the motor, and the other fan is a turbine that is connected to the transmission. In the center is another component called stator.

As the engine revolutions per minute increase, the impeller rotates at a higher speed, similar to a hydraulic pump, so that the fluid spins the second turbine, transmitting the engine's power to the transmission and then to the wheels. For its part, the stator prevents the fluid from traveling in the opposite direction so that it does not enter the impeller and slow it down.

This whole process forms a fluid coupling between the transmission and the engine so that the vehicle moves, stops at traffic lights or stops with the foot on the brake and the impeller continues to rotate, but without driving the wheels.

Unlike the clutch of the manual transmission, there is no interruption in the torque converter automatic transmission during shifting or momentary stops at traffic lights. This means gear changes without driver intervention.

Components of a Torque Converter

The components of the torque converter are:

Impeller

The impeller is a component that is connected to the motor. As its name indicates, its function is to drive the oil to the turbine, so it is considered a conductive element. When the engine is started, the impeller rotates at the same speed as the impeller, pushing the oil from its center to the outer edge.

The impeller is also known as a pump because, as it rotates, it draws fluid outward to create a vacuum that draws more fluid into the center, so that it enters the turbine.

Turbine

The turbine receives the force created by the impeller through the oil and directs it against the blades to make it rotate. This mechanism is what makes the car move. The turbine blades are curved, which means that the incoming fluid must change direction before it leaves the center of the turbine.

This change of direction is responsible for the turbine to rotate. This turbine is connected to a shaft that transfers the power to the transmission.

The fluid coming out of the turbine goes in the opposite direction of the motor and impeller. If this fluid were to hit the pump it would slow down the engine and consume fuel. To avoid this, the stator is key.

Stator

The stator is a component with a blade design that is located between the turbine and the impeller, being the component that turns the mechanism into a torque converter. Its function is to redirect the fluid that entered the turbine and return it to the impeller, changing its direction to increase its impulse as it multiplies the torque produced.

This torque multiplication is very powerful, especially when the impeller and turbine rotate at different speeds.

Inside the stator is a one-way bearing that allows it to rotate in a given direction and return the fluid to the impeller. This component is mounted on a freewheel mechanism that allows it to move when the converter elements rotate at a similar speed.

Fluid

The torque converter housing is filled with a fluid specially formulated for this mechanism. It is a blend of mineral oils with antioxidant additives, colored red to differentiate it from other automotive oils and fluids.

This fluid transfers energy between the impeller, stator and turbine so that the transmission adapts to the speed requirements of the vehicle.

Importance in Automatic Transmissions

The torque converter is an important component as it enables gear shifting and the connection of the gearbox to the engine. Thanks to this mechanism, the engine can idle, start, transmit power efficiently and without the need for a traditional clutch.

Pros and Cons of Torque Converters

The advantages of the torque converter are:

• It is a robust mechanism, which has the same service life as the engine.
• The torque converter is more reliable than the conventional clutch.
• Its maintenance is more economical since it only requires a change of transmission fluid approximately every 60,000 km.
• It is a mechanism capable of multiplying power quickly.

The disadvantages of the torque converter are:

• In case of torque converter failure the ATF stops circulating properly, so the gears become slippery and acceleration decreases.
• Torque converter slippage can cause the ATF to overheat, which can accelerate transmission wear.

Is Your Torque Converter Healthy?

Diagnosing a faulty converter might be difficult at first, because the symptoms could point to other problems with the transmission. The early signs could be leaking transmission fluid, slippage between gears, slow acceleration, unusual noises, or engine overheating, most of which will probably cause the “check engine” light to come on. And if torque isn’t controlled properly, the ride will be rough and jerky as gears won’t shift properly.

Maintenance and Care of Torque Converters

Depending on what’s wrong, the solution to a bad converter is fairly straightforward. One of the several parts—the stator, impeller pump, turbine, bearings, clutch, or clutch solenoid—may need to be replaced. If leaking fluid is the culprit, replacing a seal could solve the problem. The cost of torque converters or their parts isn’t terribly expensive, but unfortunately it’s labor-intensive, as the entire transmission may have to be removed in order to make repairs or replacements.

The maintenance of the torque converter is essential for its proper operation. For this purpose, the oil level should be checked with the dipstick and replaced approximately every 40.000 miles, or topped up if the level is low. The choice of ATF should be made based on the manufacturer's manual or the mechanic's recommendation.

In addition, it is important to check the vehicle periodically for cracks or oil leaks and, in case you notice red oil in the gearbox or under the vehicle, you should take it to the mechanic as soon as possible.

Should I Be Concerned?

Any transmission-related problem should get attention as soon as possible. Unreliable shifting can lead to accidents, or, in the case of a fluid leak, your car may experience serious damage if the issue isn’t addressed. At the very least, poor torque converters may result in poor fuel economy—and with today’s gas prices, that’s something you want to avoid.

Help’s Around the Corner

If you need help with your transmission, Sun Transmissions has what you need. Offering a full range of top-quality automatic transmission parts and equipment, such as TSS parts, solenoid parts, transmission Overhaul kits, and more, Sun Transmissions also has the best in power steering parts and many auto accessories. Visit our Miami location or place an order online.