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Bad torque converter symptoms: How to diagnose & fix

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Bad torque converter symptoms: How to diagnose & fix
A torque converter is a crucial component found in vehicles’ automatic transmission systems. It serves as a fluid coupling device that allows the engine to transfer power to the transmission and ultimately the wheels. 
 
However, torque converters can sometimes fail due to a variety of reasons. One common issue is fluid contamination or deterioration, leading to decreased efficiency and overheating. 
 
Recognizing early signs of a malfunctioning torque converter can prevent hefty repair costs.  
 

What’s a torque converter?  

A torque converter is a complex hydraulic and mechanical device that allows an automatic transmission-equipped vehicle to transfer power from the engine to the transmission and ultimately to the wheels. 
 
A key benefit is its ability to transmit torque smoothly, allowing a vehicle to come to a stop without stalling the engine. 
 
A torque converter allows the engine to continue running while the vehicle is at a standstill, and it provides a smooth and automatic way to change gears without the need for a clutch pedal.  
 

How does a torque converter work? 

In vehicle torque converter acts as a hydraulic coupling connecting the engine to the transmission. 
 
In simple terms, imagine two electric fans placed facing each other. When you switch on one fan, the air it blows causes the other fan's blades to rotate. This is a great way to visualize the basic principle behind a torque converter. However, instead of air, a torque converter uses a transmission fluid to transmit power. 
 
Now, let's delve deeper into the torque converter and better understand its key components: 
 
  • Flywheel (engine's flex plate). Attached to the engine, the flywheel is the driving force. It's akin to the first fan that's switched on, setting everything else into motion. 
  • Pump (impeller). Fixed to the torque converter housing, the pump is like our blowing fan. When the engine spins the flywheel, the pump also spins, circulating fluid throughout the converter. 
  • Turbine. The turbine is connected to the vehicle's transmission input shaft, acting much like the second fan that isn't powered itself but spins in response to the fluid moved by the pump. This spinning motion is transferred to the gears of the transmission. 
  • Stator. Located in the center, the stator redirects the transmission fluid returning from the turbine back to the pump. This redirection is crucial for increasing efficiency and torque when the vehicle is accelerating from a stop. At steady speeds, the stator's job is less critical, but it's vital for a smooth and efficient takeoff. 
  • Torque converter housing. This houses all the components and connects to the flywheel, ensuring that the engine's rotary motion is contained and transferred efficiently. 
Torque converter scheme
 

What does a torque converter do in automatic transmission? 

When a vehicle is at a stop or idling, the impeller spins, creating fluid movement within the torque converter. As you press the accelerator pedal, the impeller spins faster. This leads to more forceful fluid flow. 
 
This fluid flow strikes the turbine blades, which causes them to rotate and transfer rotational energy to the transmission’s input shaft.  
 
When the vehicle accelerates, the stator rotates freely, allowing fluid to return from the turbine and flow through it without much resistance. 
 
This fluid redirection helps increase the torque transmitted to the turbine. However, during deceleration, the stator locks, preventing the reverse fluid flow and minimizing power loss.  
 
Overall, a torque converter allows the engine to keep running while the vehicle is stationary. It also gives smooth engagement from a standstill and provides the necessary torque multiplication for efficient acceleration.   
 

Which vehicles have torque converters? 

Typically, most automatic transmission vehicles have a torque converter. Also, while some Volkswagen Group (VAG) and BMW models employ dual-clutch systems, others, especially luxury models, utilize torque converters.   
 
Cars with manual transmissions, electric vehicles, those with dual-clutch transmissions like the DSG (Direct Shift Gearbox) found in many VAG models, and vehicles with CVT (Continuously Variable Transmissions) and AMT (Automated Manual Transmissions) – don't use torque converters.   
 
A blue BMW 2023 7 Series sedan driving on a highway with mountains in the background

What are the bad torque converter symptoms? 

A torque converter can malfunction for a variety of reasons, and these issues can lead to poor performance, reduced fuel efficiency, and even complete transmission failure. Some common symptoms of failing torque converter include:  
 
Dirty transmission fluid 
 
Transmission fluid can become contaminated with debris, dirt, and metal particles and lead to poor lubrication, overheating, and increased friction within the torque converter.  
 
Automatic transmission fluid leaks
 
Leaks in the torque converter's seals, gaskets, or transmission fluid lines can lead to a drop in fluid levels, which can negatively impact performance and overheating.  
 
Clutch slipping
 
Even though automatic transmissions do not have a traditional mechanical clutch plate, they still have clutch packs. If these clutches wear out, break, or fail to engage properly, it can lead to slipping, shuddering, or loss of power transfer.  
 
Overheating
 
If the transmission fluid isn't cooled properly or if the vehicle is subjected to heavy loads or towing without the appropriate transmission cooler, the torque converter can overheat, leading to fluid breakdown and component damage.  
 
Rough acceleration 
 
When an automatic car's transmission fluid is low or dirty, it can lead to hesitant and jerky gear shifts during acceleration. Worn internal transmission parts can also cause the vehicle to struggle to pick up speed smoothly. 
 
Gear slippage
 
If the transmission fluid isn't at the right level or has lost its integrity, it may result in gear slipping, which feels like the car is changing gears for no reason. Additionally, damaged internal components such as worn clutches or bands can cause the car to slip out of gear, leaving you with an uneasy and unpredictable drive. 
 
Gear shift problems
 
Malfunctioning solenoids or valves can disrupt the hydraulic pressure and flow within the torque converter, resulting in erratic shifting and poor performance.  
 
Rough idling
 
Among many other reasons why a car shakes when idle, contaminated transmission fluid can cause a rough idle, where the car feels bumpy and unstable while sitting still. Malfunctioning torque converter components, such as a damaged stator, can also lead to a shaky experience even when the car isn’t moving. 
 
It's important to note that symptoms of bad torque converter can vary depending on vehicle model. Symptoms can range from transmission slipping, shuddering during acceleration, rough idling, shaking in certain gear, unusual noises, delayed or rough shifting, and even complete transmission or torque converter failure. 
 
So, what to do? 
 
If you experience any of these symptoms, it’s best to call your mechanic for accurate diagnostics and transmission repair.   
 
A mechanic is performing an oil change on a car elevated on a lift
 

How to prevent a torque converter failure?  

Treating your car right can save you a lot of hassle and unplanned expenses. Here are some steps you can take to prevent torque converter problems:  
 
  • Use the right transmission fluid. Using the wrong type of fluid can lead to torque converter and transmission problems.  
  • Avoid overheating. Ensure your vehicle's cooling system is in good condition and avoid heavy towing or driving in extreme conditions that could cause excessive heat buildup.  
  • Check transmission fluid levels. Low fluid levels can lead to inadequate lubrication and low hydraulic pressure, which leads to slower engagement when shifting gears.  
  • Pay attention to your driving habits. Avoid abrupt starts, aggressive acceleration, and sudden stops. These behaviors can put extra stress on the torque converter and transmission.  
  • Use parking brake. When parking, engage the parking brake before shifting into "P." This reduces the strain on the parking pawl within the transmission, which indirectly affects the torque converter.  
  • Perform regular checks. Using scanning or diagnostics tools like OBDeleven NextGen is a great way to keep track of your vehicle's performance and health. It can help you identify any issues with your transmission system by showing you the transmission fault codes
 
Additionally, you can view live data parameters like torque converter hydraulic pressure, transmission fluid temperature, selected gear, and torque converter clutch slipping, which can help you stay on top of your car's maintenance needs. 
 
A person in the driver's seat of a Volvo car is holding a smartphone with an OBDeleven diagnostic application and scanning Transmission control unit

To wrap up   

The torque converter's health is paramount for smooth driving. Preventing its malfunction requires a combination of responsible driving practices and regular maintenance. 
 
By being proactive and attentive, you can ensure the longevity and optimal performance of your vehicle's torque converter and transmission. OBDeleven is here for you to OBDeleven is here to help you keep an eye on your vehicle's health – whenever you need, easily. 
 
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