What Is Torque Converter and How Does it Work?

The powerplant in a vehicle produces rotational energy called torque. The transmission is then responsible for sending that energy to the wheels.

To do that, a traditional automatic transmission — found in everything from a Dodge Challenger to a Volkswagen Jetta — relies on a device called a torque converter that sits between it and the engine.

This important component acts much like the clutch of a manual transmission in that it transmits power from the engine to the transmission and thereby gets your vehicle rolling.

What is a Torque Converter?

A torque converter is a device, usually implemented as 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 prime mover to the automatic gear train, which then drives the load.

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

A torque converter serves to increase transmitted torque when the output rotational speed is low.

In the fluid coupling design, a fluid is used to transfer torque from an input impeller to an output turbine through a fixed stator. This setup increases torque on the output when the output shaft is rotating more slowly than the input shaft. Essentially, it functions as an adaptive reduction gear.

This is a feature beyond what a simple fluid coupling provides, which can match rotational speed but does not multiply torque.

Fluid-coupling–based torque converters also typically include a lock-up function to rigidly couple input and output and avoid the efficiency losses associated with transmitting torque by fluid flow when operating conditions permit.

What Does A Torque Converter Do?

In cars, the turning of the engine’s crankshaft produces torque. This is what allows you to accelerate your car. The more torque your engine produces, the faster it goes.

The torque converter is what transmits that torque from the engine to a rotating driven load. In an automatic transmission car, the torque converter connects the power source to the load.

It also have other functions, including:

• Connecting the engine to the transmission
• Transmitting power
• Pressurizing transmission fluid
• Allowing the engine to run while the wheels stop

How Does a Torque Converter Work?

A torque converter is designed to function in three different phases depending on input from the driver.

Stall—During the stall phase, the engine and the impeller are turning, but the turbine cannot turn, so the car does not move. Stall happens when the car engine is running, the transmission is in gear, and the driver has their foot on the brake so the car isn’t moving.

Acceleration—When the driver presses the gas pedal, the acceleration phase begins. One of the most important characteristics of this phase is the multiplication of torque.

Torque peaks just as the vehicle starts moving, while the impeller is spinning much quicker than the turbine. Then, torque decreases to nearly zero once the impeller and turbine approach the same rotational speed.

Coupling—The coupling phase happens at high vehicle speeds. The impeller and turbine speeds are rotating at nearly the same speed at this stage. Many models lock the two together with a friction clutch to eliminate slippage and increase efficiency.

Bad Torque Converter Symptoms

There are several signs that you might have a torque converter issue:

#1. Loss of Acceleration.

If your vehicle feels more sluggish than normal or it is physically shuddering when you step on the gas pedal—as if it’s struggling to accelerate as it typically would—this is a sign that there could be a transmission problem and the torque converter is a likely culprit.

#2. Slipping Between Gears.

Automatic vehicles should shift smoothly between gears. You can usually feel it to some extent, especially when you accelerate or decelerate quickly. However, you may also feel the vehicle slipping as it shifts between gears or notice that it is having trouble staying in a certain gear.

If the shifting feels rough or strange, there’s a good chance that you have a torque converter issue.

#3. The vehicle Won’t Shift at All.

A surefire sign of a failing torque converter is when the vehicle won’t shift into a specific gear at all. If you can’t get it to go into reverse or forward drive won’t engage, then it’s probably something wrong with your torque converter.

#4. Transmission is Overheating.

Like your engine, your transmission has a sensitive temperature gauge that will warn you if the transmission is overheating.

An overheated transmission is a major concern, so you’ll want to get your vehicle looked at by a transmission specialist as soon as possible. It may be a failing torque converter or some other internal damage that needs to be addressed.

#5. Transmission Fluid Leak.

Transmission fluid is vital to the health and performance of the torque converter (and the transmission system as a whole). Torque converter seals can be damaged easily or get worn out with time, so they are a common source of transmission fluid leaks.

Any time you see transmission fluid leaking, you don’t want to take chances. It’s an early warning sign that something is wrong and it can lead to major internal damage if left ignored.

#6. Bad Transmission Fluid.

If you check your transmission fluid and notice that it is dark, burnt, milky or filled with debris like metal shavings, then you’ll want to get your transmission serviced right away. That may be all you need to get fresh fluid running through the system again.

It could also be the sign of internal transmission or torque converter problems, so a proper inspection from an expert transmission technician is also a good idea.

Causes Of A Bad Torque Converter

Torque converters, despite their robust construction, are not immune to wear and tear. Several factors can contribute to their deterioration and eventual failure. Let’s explore some of the common culprits:

High Mileage: As with any mechanical component, the lifespan of a torque converter is limited. As your vehicle accumulates mileage, the internal components of the torque converter experience wear and tear, leading to potential issues.

Overheating: Excessive heat is a nemesis of automatic transmissions, including the torque converter. Overheating can be caused by various factors such as towing heavy loads, driving in extreme temperatures, or a malfunctioning cooling system. The intense heat can damage the delicate seals and components within the torque converter, impairing its functionality.

Contaminated Transmission Fluid: Transmission fluid plays a vital role in lubricating and cooling the torque converter. If the fluid becomes contaminated with debris or metal shavings, it can wear down the internal components and disrupt the smooth operation of the torque converter. Regular transmission fluid changes are crucial for maintaining the health of your torque converter.

Defective Needle Bearings: Needle bearings within the torque converter facilitate smooth rotation and power transfer. Over time, these bearings can wear out or become damaged, leading to noise, vibration, and potential failure of the torque converter.

Worn-Out Clutch Lining: The clutch lining inside the torque converter is responsible for engaging and disengaging the transmission. Wear and tear on the clutch lining can result in slippage, shuddering, and reduced efficiency.

Defective Torque Converter Solenoid: The torque converter solenoid controls the flow of transmission fluid to the torque converter clutch. A malfunctioning solenoid can disrupt this process, leading to problems with engagement and disengagement.

How To Fix A Bad Torque Converter?

So, you suspect your torque converter might be acting up. Now what? Well, the good news is that several potential solutions exist, depending on the specific symptoms you’re experiencing. Let’s explore some common scenarios and how to address them.

#1. Shuddering Or Gear Slipping.

Experiencing shuddering or gear slippage? It’s time to inspect the transmission fluid. Low fluid levels can definitely lead to these issues. If the fluid appears dark or has a burnt smell, that’s a telltale sign of contamination.

In this case, a simple fluid change might do the trick. However, if the shuddering persists, the torque converter itself might be damaged and require replacement.

#2. Contaminated Fluid.

Contaminated transmission fluid is a serious issue that can wreak havoc on your torque converter and the entire transmission system. If you suspect contamination, a complete transmission flush is in order.

This process involves removing all the old fluid, cleaning the system, and replacing it with fresh, clean fluid. While this might seem like a drastic measure, it’s crucial to prevent further damage and ensure the longevity of your transmission.

#3. Overheated Transmission.

An overheating transmission can spell trouble for your torque converter. If you’ve noticed your transmission running hot, it’s essential to identify the root cause. This could range from low fluid levels or a malfunctioning cooling system to a more serious internal problem.

Addressing the underlying cause of overheating is crucial to prevent damage to the torque converter and other transmission components.

cost to replace a torque converter

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.

FAQs.