Everything You Need To Know About Hydraulic Torque Converters

The hydraulic torque converter is a mechanical device that uses fluid hydrodynamics to enable the engine to spin autonomously without the transmission. It is a component of the automatic transmission in automobiles and performs a similar function to the clutch in a manual transmission vehicle.

How does a torque converter operate?

The torque converter is comprised of three major components that work alongside each other. These are the impeller, the turbine, and the stator. The impeller forms the first part of this device’s assembly. Within it is a fluid that enables it to spin alongside the engine’s crankshaft. As it spins faster, the fluid flows through it at a higher velocity thus exerting more force.

Once the fluid has passed through the impeller, it flows into the turbine. As the fluid hits the blades, it is directed towards the internal section of the turbine and finally finds its way back to the impeller. The complete circulation of the transmission fluid between the impeller and turbine is what is known as the fluid coupling.

The stator performs the task of reversing the transmission fluid and sending it back into the impeller. This process slows down the fluid, and as it returns into the impeller to maintain the cycle it generates torque.

The stages of a torque converter’s operation

A torque converter performs different functions in three main stages namely, stall, acceleration, and coupling. When the vehicle is stationary, the engine delivers power to the impeller. However, the impeller does not spin since the brake pedal has been depressed, e.g at a stop signal. As such, the engine does not stop.

During acceleration, the impeller begins to spin a lot faster creating a steep gradient between the turbine speed and impeller speed. This results in torque which is then multiplied by the converter to cause acceleration. Finally, once the vehicle has attained top-speed, both the impeller and turbine now rotate at the same speed, and the torque increase stops.

At this juncture, the torque converter has been reduced to a mere fluid coupling. Automatic transmission systems use lockup clutches to bind the turbine and the impeller together in order to eliminate loss of power and aid in smooth transmission.

Common problems related to torque converters

Sometimes a problem with the torque converter can be misinterpreted as a sign of a failing transmission. This is usually far from the truth. All you need to do is to take your vehicle for diagnosis by a professional transmission mechanic. It is only then that you will be able to identify the specific issue.

Symptoms of an ailing torque converter are usually similar to those of a failing transmission system. The following are some telltale signs that should raise your concerns:

Shuddering and shaking

Whenever your vehicle begins to shake and shudder once you hit 35-40 mph, this could mean that your lockup clutch is defective or needs some repairs. An old lockup clutch makes accelerating into top speed an uncomfortable experience.


Regular overheating could signify low levels of transmission fluid. This results in low pressure thus hindering the proper functioning of the torque converter.


In case you have damaged fins within the hydraulic torque converter, this can cause your transmission to falter as it shifts. At times it can even completely slip out of gear because engine power is not undergoing conversion into the requisite hydraulic pressure for gear shifting.

An increase in stall speed

A defective torque converter can result in the transmission delay in coupling with the engine. This might result in high stall speed.

Lastly, to maintain a healthy automatic transmission system, always use the right transmission fluid and ensure it is at the correct level. This can be achieved through an appropriate maintenance schedule.