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How a Torque Converter Works

Automotive transmissions were all manually operated when initially introduced.  If the engine was directly connected to the gearbox and the rest of the driveline, the vehicle would stall any time that the vehicle came to a stop.  In order to come to a stop and keep the engine running, a clutch is used to separate the connection between the engine and the gearbox.  This manual system was used from the invention of the automobile up until the 1930s.  A German engineer by the name of Herman Fottinger devised and received a patent in 1905 on a fluid drive and torque converter, beginning the move towards an “automatic” transmission.  Fottinger licensed his torque converter to a number of companies in the 1930s, including the Chrysler Corporation.  In 1939, General Motors became the first manufacturer to use a fluid drive in a mass-produced automobile when they introduced their Hydromatic transmission.

how a torque converter works

How a Torque Converter Works

A torque converter is essentially a fluid coupling system that takes the place of a clutch assembly in a manual transmission.  It allows the engine to turn independently from the transmission.  When you are at a stop, the engine is turning slowly and the amount of torque going through the torque converter is low.  As you step on the gas and the engine revs higher, the amount of torque transmitted to the torque converter increases and the vehicle begins to move.

A torque converter is basically made up of an impeller, turbine, stator, clutch and transmission fluid.  The impeller has blades like a fan and is turned mechanically by the engine.  As the engine picks up speed, the impeller spins faster which in turn pushes the transmission fluid faster.  The transmission fluid then hits the turbine, which is a fan similar to the impeller and turns the transmission shaft.  The problem with this is that the transmission fluid is moving in the opposite direction of the engine, so it will begin to drag on the torque converter housing and slow everything down.  That brings us to the stator, which is another fan-shaped device that takes the transmission fluid in and reverses direction, reducing drag and increasing efficiency in the unit. 

The last piece, the lock-up clutch, allows the impeller and turbine to lock together at higher speeds which reduces slipping and in turn increases the fuel efficiency of the system.  Packard and Studebaker had used a lock-up clutch back in the 1940s, but the design was dropped due to the increased cost of production.  However, the fuel shortages of the 1970s forced automakers to look at ways to increase fuel efficiency.  The lock-up clutch was reintroduced by Chrysler in 1978 and General Motors followed suit in 1979.  Since then, the lock-up torque converter has become an industry standard.

torque converter

All these pieces work together to allow the torque converter unit to take the power of the engine and transmit it as needed to the transmission gear assembly.  A torque converter works in 3 phases: stall, acceleration, and lock-up.  During “stall”, the engine is turning as is the impeller.  However, the turbine is not moving and as a result the vehicle does not move.  During the acceleration phase, the engine drives the impeller and increases the velocity of the transmission fluid, which in turn increases the speed of the turbine (and thus the rest of the vehicle).  The final phase lock-up, usually occurs at speeds above 40 miles an hour and allows the engine and transmission to turn at the same speed, without any residual slipping or loss of efficiency.

Common Problems

The complexity of the parts working inside of a torque converter means that they do in fact give out over time.  High heat can warp the outside case of the torque converter and can cause the seals to break down, which will result in leaks.  As transmission fluid leaks out of the torque converter, there is less fluid inside which results in even greater heat and more damage.  In fact, the heat and pressure inside of a torque converter can reach a level that the torque converter will balloon up and burst!  The constant flow of transmission fluid through the blades of the impeller and turbine can eventually wear the blades to a degree that they break, which then puts metal pieces inside of the torque converter and that leads to more damage.  The stator clutch can become locked up and this leads to a huge drop in fuel efficiency.  The stator clutch itself can also break, and then the vehicle might not move at all.  Keep in mind, the transmission fluid within the torque converter is shared with the actual transmission.  Any breakdown in the torque converter causing contamination of the transmission fluid will likely result in components within the transmission failing.

There are some signs to watch for if your torque converter is on its way out.  The transmission might start to slip, and you may feel a significant shudder in the vehicle when first starting out or when driving at a constant, slower speed.  Another sign that the torque converter is wearing out will be excessive heat.  Some cars, trucks and SUVs are equipped with a transmission temperature warning light, and that will let you know there is a problem.  In vehicles without them, overheating in the torque converter can lead to the vehicle going into failsafe mode where the vehicle starts off in a higher gear and will not shift out of that gear.  Also, as mentioned before, a worn out or malfunctioning torque converter may start to leak and show signs of contamination in the transmission fluid as parts inside the torque converter break down.

Transmission Specifics: The 6L80 (and the similar 6L90) transmission from General Motors was introduced in 2005 and is still used today.  A six-speed transmission designed for use in rear wheel drive vehicles, it has been used in Chevrolet and GMC pickups, the Cadillac Escalade and GMC Yukon Denali, and the high-performance Chevrolet Camaro and Corvettes.  Over the years, the 6L80 has become well known for torque converter issues leading to transmission failure.  A design flaw in early models leads to consistent wear between the torque converter cover and the lock up clutch.  That creates high heat, shuddering, and eventual breakdown of the case itself which spreads metallic pieces throughout the transmission.

What’s Involved in Repair

The good news is that we are here to help!  The Advanced Transmission Center team consist of technicians who have decades of experience diagnosing, rebuilding and repairing automatic transmissions in domestic and import vehicles.  We are your local transmission repair shop and we are the most trusted specialty shop for local dealerships and general automotive repair shops.  We have the ability to test and diagnose problems with your torque converter and use only quality parts in our repairs.  In some cases where a particular torque converter is known to have problems, Advanced Transmission Center may recommend using a heavy-duty billet aluminum torque converter.  Two reasons motivate the use of billet torque converters: faulty designs and HD applications.  There are cases where the OEM design is known to have weaknesses that lead to premature failure, and an upgraded torque converter might be the solution to get your vehicle back on the road for years to come.  In addition, a billet torque converter works well for vehicles facing load applications near or beyond its OEM limits.  This is particularly a great option for construction vehicles, trucks that tow, offroading vehicles, work trucks, etc.

At Advanced Transmission Center, EVERY in-house transmission rebuild includes a fully remanufactured torque converter.  Unlike second-tier transmission repair shops, we believe the integrity of a rebuilt transmission is compromised if the old torque converter is reused.  We partner with a local Denver-based machine shop that exclusively focuses on rebuilding automatic torque converters.

If you are having problems with your torque converter or any other transmission-related issue, contact Advanced Transmission Center at either of our locations and we’d be happy to help!  Unlike dealerships or many independent repair shops, we are transmission specialists trained to fix issues related to a vehicle’s drive-train.  You can reach out to either location that is most convenient for you.

Advanced Transmission Center – Lakewood 1194 S Pierce St Lakewood, CO 80232 PHONE: 303-816-3856 Manager: KeithAdvanced Transmission Center – Westminster 3686 W. 72nd Ave Westminster, CO 80030 PHONE: 303-647-5257 Manager: Anthony

Please give us a call or send us a message ASAP.  We look forward to serving your vehicle drivetrain and transmission needs.  Over 35 years, our goal remains to be “Geared for Customer Satisfaction!”

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