What Is Torque Converter and How Does it Work?

What is Torque Converter?

A torque converter is a type of fluid coupling that transfers rotating power from a prime mover, like an internal combustion engine, to a rotating driven load. In a vehicle with an automatic transmission, the torque converter connects the power source to the load.

It is usually located between the engine’s flexplate and the transmission. The equivalent location in a manual transmission would be the mechanical clutch.

The main characteristic of a torque converter is its ability to increase torque when the output rotational speed is so low that it allows the fluid coming off the curved vanes of the turbine to be deflected off the stator while it is locked against its one-way clutch, thus providing the equivalent of a reduction gear.

This is a feature beyond that of the simple fluid coupling, which can match rotational speed but does not multiply torque, thus reduces power.

How Does a Torque Converter work?

It’s a bit difficult to understand how fluid can provide the power to move something as essential as a vehicle. A pump helps achieve torque control that works by circulating fluid around the torque converter, which is determined by the rotation of the crankshaft.

A turbine is located in the housing and rotates when the pumped fluid comes into contact with the turbine blades. In this way, the torque that is transmitted to the transmission via the input shafts can be measured

The torque converter housing is connected to the flywheel and rotates at the same speed as the crankshaft in the turbine housing. The impeller or centrifugal pump effectively hurls the transmission fluid into the ribs of the turbine, which in turn rotates or transmits the torque to the transmission.

The stator is the barrier that directs the fluid back into the turbine instead of the pump, thereby increasing the efficiency of the system. When the vehicle is idling, the speed at which the transmission oil pumps into the turbine is slow, which means that very little torque is getting through the transmission to the engine.

As the crankshaft spins faster and more momentum spins the flywheel, the fluid moves faster from the pump to the turbine, forcing the turbine to spin faster, allowing more torque through the transmission.

It is important to note that the insides of the torque converter are still a mystery. The basic mechanics may be understandable, but the complicated calculations and engineering behind it is best understood with someone with an advanced understanding of fluid mechanics.

Torque Converter Diagram

6 symptoms of bad torque converter

Isolating and diagnosing a problem with the torque converter without disassembling the transmission/ drivetrain is not easy, but there are several symptoms to look for. Some of the signs of a malfunctioning torque converter are: shudders, dirty fluid, shifting gears at high revs, and strange noises like clicking or purring.

1. Slipping

Because a torque converter is responsible for converting the engine torque into the hydraulic pressure required to shift gears in the transmission, a damaged rib or bearing can cause the transmission to delay a shift or slip out of gear.

Slippage can also be caused by insufficient or excessive fluid in the transmission. There may also be a loss of acceleration and a noticeable decrease in your car’s fuel consumption. Be sure to check your fluid level before you take your car to a store.

2. Overheating

If the temperature gauge shows that your car is overheating, it could be a sign that the fluid pressure has dropped and there is a problem with your torque converter. If a converter overheats, it cannot transfer power from the engine to the transmission.

This leads to poor throttle response and excessive wear and tear on the internal functioning of the transmission. Low fluid levels or a defective magnet can also cause the gear unit to overheat.

3. Shuddering

When the lock-up clutch in the torque converter begins to fail, there may be a shudder at around 30-45 mph. The feeling is very noticeable and usually feels like you are driving over a bumpy road with lots of small bumps.

When the converter switches to direct drive, a worn lock-up clutch can make the transition difficult, leading to this feeling. The feeling can start and stop abruptly and not last long. However, if you’ve experienced it multiple times, it’s time to get your transmission checked.

4. Contaminated Transmission Fluid

A torque converter is filled with automatic transmission fluid (ATF). If the fluid is contaminated, the parts inside can be damaged. This can lead to worn bearings on the stator or damaged fins on one of the turbines.

If you notice a significant number of black sludge/dirt/debris in the fluid, it could mean that the converter or the gearbox itself is damaged. If this happens, change the fluid and drive around for a while before checking the fluid again. If the problem persists, have a professional check your car.

5. Higher Stall Speed/Gear Engagement RPM

The “stall speed” is the point at which the engine speed is high enough for the torque converter to transfer power from the engine to the transmission. In other words, it is the speed at which the converter stops increasing the engine speed when transmission power is prohibited.

If the torque converter is defective, it cannot correctly transfer the rotational force of the engine to the hydraulic pressure. This results in the transmission taking longer to switch on the motor, which increases the lock-up speed. Here’s how to do a stall speed test. You need to find out how fast your vehicle is stopping beforehand (usually 2000-2500 RPM).

6. Strange/Unusual Sounds

It’s not uncommon for the torque converter to emit strange noises as it begins to fail. Some of the sounds you might hear include a ‘whirring’ sound coming from bad bearings, or ‘clinking’ sound coming from a broken turbine fin.

How to Diagnose the Problem

Here is how you can try diagnose the problem yourself. At each step, listen carefully for unusual slipping, shuddering, lurching forward or strange noises:

  • Start your car and let it run for a couple minutes
  • Press the gas down lightly several times
  • Push the brake and shift the car into drive
  • Slowly shift through each gear
  • Drive around the block, listening carefully every time you accelerate

Do Not Drive with a Broken Converter

Important to note – a converter can slowly fail over several weeks or even months before it fails completely. Driving a vehicle with a damaged vehicle can be risky as it can completely dissolve if it collapses and introduces scrap metal into the transmission fluid.

The contaminated transmission fluid can then get into the transmission and cause considerable damage or even complete failure, as a result of which a simple exchange of the converter can become an expensive repair or an expensive exchange of the transmission. To prevent this from happening, pull the road if it is safe and turn off the engine.

Common Causes of Torque Converter Problems

There are a few reasons why problems can occur. Don’t assume what the problem is until you have your transmission looked at, but here are some general ideas of what it could be.

1. Bad Torque Converter Needle Bearings

The impeller, turbine and stator use needle bearings to be able to rotate freely. The bearings separate these rotating components from the converter housing. If these bearings are damaged, you will notice decreased performance, strange noises, and metal parts in the gear fluid due to metal-to-metal contact/grinding.

2. Damaged Torque Converter Seals

If you notice a leak of transmission fluid from the bell housing, the torque converter seal may be damaged. If your torque converter can’t hold the right amount of ATF, it can’t effectively transfer power from the engine to the transmission.

This leads to overheating, shifting problems, strange noises, higher stall speeds and slipping between gears. The bad seal must be found and replaced.

3. Worn Torque Converter Clutch

Automatic transmissions have a number of clutches throughout the assembly. A torque converter clutch is responsible for locking the engine and transmission in the direct drive.

If the torque converter has been burned from overheating, jammed or blocked from deformation, or contaminants in the transmission fluid have damaged the friction material, your car may keep moving even though you come to a stop. The converter can also wobble and fail to engage the direct drive if the friction material on the clutch disc wears out.

4. Faulty Torque Converter Clutch Solenoid

A torque converter clutch solenoid valve regulates the amount of transmission fluid that the converter lock-up clutch receives. If this electronic device cannot accurately measure the fluid pressure, the lock-up clutch will not work properly due to excessive or insufficient fluid supply. This can lead to loss of direct drive function, poor mileage and engine stalling.

Torque Converter Replacement Cost

If you’ve noticed one or more of the above symptoms, it is possible that your torque converter is not working properly. The cost of repairs may be higher than replacing them. It is therefore essential to have a mechanic/technician take a look.

If you plan to do the job yourself, the estimated repair cost is between $ 150 and $ 500.

Repair shops charge between $ 600 and $ 1000 to replace a torque converter.

The torque converter itself is relatively inexpensive (between $ 150 and $ 350 depending on the vehicle), but it takes 5 to 10 hours of work because the transmission must be removed to replace the torque converter.

At the same time, the fluid should be flushed/changed, which may or may not be included in the price a store is offering you.