Troubleshooting Your Car’s Torque Converter

If you’re noticing your car shuddering or slipping gears, overheating, or weird sounds coming from the transmission, there might be an issue with your torque converter.

Torque converters are designed to transfer the power from your engine and transmit it to your transmission, rear-end gears, and ultimately to the tires. It also helps to smooth out the bumps on the road while driving.

The Impeller


The impeller, a fan-like part found in the front of a torque converter, provides engine horsepower to your car’s transmission. It also pumps hydraulic fluid inside the converter body to keep it cool and functioning at its best.

The blades on the impeller spin at a very high speed, creating a pressure that causes transmission fluid to move faster than it would without the device. The fluid then moves onto the next part of your torque converter, a turbine.

A turbine is similar to an impeller, except it has angled blades that are found opposite of the impeller’s curved blades. When the transmission fluid hits the turbine’s angled blades, it starts spinning, turning your vehicle’s pump and transmission shaft.

This action creates a vortex in the fluid and increases its flow rate. This is a useful feature in many applications, including air pumps used to move air through ventilation systems and superchargers for internal combustion engines.


Another application for an impeller is in the agitator in top-loading washing machines. These agitators have blades that resemble an Archimedes screw, which is an early form of an impeller.

There are several different types of impellers, but the basic design is to sling fluid into the next piece in your vehicle’s torque converter, called the stator. The stator is a wheel that acts as a control unit and multiplies torque by redirecting oil that slings off the impeller into the turbine, where it helps rotate the turbine.

When the impeller and turbine speeds are at nearly the same rpm, it’s called the coupling phase. At this time, you can begin to accelerate your vehicle, as torque multiplication occurs. The torque that is generated can be converted into electricity by your car’s electrical system, and it’s a great way to get your vehicle moving when you need it.

The Stator

The stator is an essential part of the car torque converter. Its function is to control the flow of fluid through the converter and help it multiply its incoming torque.

The rotor is also an important component of the converter. It is connected to the input shaft of the transmission and rotates as the fluid is pumped from the stator.

Stators have a variety of designs to accommodate different outputs, frequencies, and voltages. Typically, they have three-phase windings that are supported by high-grade silicon steel stamping.

Some stators have a single winding to make them easy to manufacture and replace. Other stators have multiple windings that provide a greater amount of power and reduce the number of parts to replace them.

Both the stator and the rotor are made from steel portions that are stacked together. These are called laminations, and they can be welded or bonded to each other depending on the application.


AC supply

When an AC supply is applied to the stator, it induces a magnetic field in the core of the rotor. The magnetic field is then converted to a rotating electric current through the rotor’s winding.

There are several types of rotors including squirrel cage and phase wound. They all have a winding that is excited by the DC supply.

The rotor is the heart of the stator and contains a core and a winding that’s connected to the three-phase supply. It is the main rotating section of the motor and carries a constant magnetic field.

Moreover, the rotor’s winding is connected to the commutator. This is a crucial element of the electrical system since it transfers the power to and from the coils of the rotor.

A torque converter’s stall speed is one of the most significant factors in how it performs. This is the rpm rating at which it will no longer be capable of transmitting its full-rated torque to the pump. This stall speed varies by type of vehicle, rear differential ratio, the weight of the vehicle, tire size and compound used, transmission shift ratios, and many other factors.

The Turbine

A car torque converter is a component of an automatic transmission that multiplies the engine’s power (torque) to send it to the wheels. It’s a complex system that consists of a pump impeller, a turbine, and a stator.

The impeller is a fan-like part with angled blades that turns because of centrifugal force from the engine. It moves the fluid through its blades and then into a turbine, which is a closely matching piece found on the opposite side of the impeller.

When the fluid strikes the turbine’s angled blades, it starts spinning, turning the pump and transmission shaft in your vehicle. The liquid then enters the stator assembly.

The stator senses the speed of the impeller and the turbine and, if the speed difference is too great, it applies a reaction torque to the fins in the stator. This stops the stator from spinning and re-enters the impeller at a more severe angle, causing it to rotate faster than the turbine.

Action multiplies

This action multiplies the torque in a way that is more efficient than a simple fluid coupling, which matches rotational speed but doesn’t multiply torque. The stator is the most important part of a torque converter.

Torque converters work differently depending on the driver’s input. The driver’s throttle control determines how much of the torque converter’s output is used for acceleration and braking, and what speeds the converter achieves the coupling point.

The coupling point is where the turbine and impeller are able to rotate at the same rate, at which they start eliminating the buildup of torque. At that point, a slip-controlled lockup clutch engages to lock the turbine and impeller together. This eliminates slipping between the two parts of the converter and allows it to operate at 100 percent efficiency, which is very important for fuel economy.

Torque converters cannot be completely efficient until a locking process occurs. This process removes any friction between the impeller and turbine, allowing for greater energy transfer and less power loss. The locking process is computer-controlled, which makes it a more efficient and safer method than a manual transmission.

The Working Fluid

A torque converter, sometimes referred to as a clutch, is the fluid coupling that takes the place of a mechanical clutch in an automatic transmission. This fluid coupling prevents the engine from stalling when you stop your vehicle, while also allowing it to change gears independently of the driver.

Torque converters have been designed to multiply the torque of the engine by two or three times when you accelerate out of a stop. The torque converter also helps to reduce fuel consumption and improves overall car performance.

The working fluid of a torque converter is called transmission fluid. It is typically a blend of petroleum and water. It is pumped through the transmission by the engine. The pump in a torque converter is a centrifugal type.

When the fluid moves through the impeller it creates a vacuum that draws more fluid in at the center of the pump. This causes it to spin faster than the fluid would have if the fluid were allowed to move straight through it.

Read more: Different Car Catalytic Converters and Components

Fluid flows back

As the fluid exits the impeller it moves through the turbine, a nearly identical bladed piece that sits opposite the impeller. The fluid hits the angled blades of the turbine and causes it to start turning.

Then, the fluid flows back into the center of the turbine and hits the impeller again. This time, the fluid is redirected into a series of fan-type blades that are in the center of the turbine. These blades have a very aggressive design that almost completely reverses the direction of the fluid.

This reverses the fluid back into the impeller and causes it to spin again, pushing more transmission fluid through its blades. This process continues until the fluid reaches approximately 90 percent of the speed of the impeller.

Once the speed of the impeller is higher than the speed of the turbine, the working fluid of a torque converter has reached its peak and is essentially acting like a fluid coupling. This is the stage where most modern automakers will apply a lock-up clutch to the turbine and impeller.