• What Torque Converter To Use
• Torque Converter Automatic
• Torque Converter Rebuilders Near Me

Torque converter performance isn’t just about stall speed; it’s also about how firm a converter hooks up when it does stall. This is known as a tight or loose converter. Torque converter manufacturers like B&M, TCI Automotive, and Performance Automatic employ techniques that make torque converters more efficient with less slippage. Automatic transmission cars use a torque converter. A torque converter is a type of fluid coupling, which allows the engine to spin somewhat independently of the transmission. Torque converters are probably the most misunderstood component in an automatic transmission, yet they’re the simplest in both theory and function. Think of a torque converter like a water wheel in an old saw mill: the waterwheel is driven by fluid in motion.

• Torque Converter This is the most common automatic option, and can be found in the hugely popular Mazda range, as well as the more high-end Japanese brand, Lexus. Instead of using a clutch to engage and disengage the engine's torque from the gearbox, traditional autos keep the drivetrain connected at all times by using a torque converter.
• Automatic Transmission - Torque Converter Has Five Important Parts Your car's automatic transmission has a torque converter. The torque converter is made up of five parts: 1.

A torque converter is a type of fluid coupling which 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.

Hydraulic systems[edit]

By far the most common form of torque converter in automobile transmissions is the hydrokinetic device described in this article. There are also hydrostatic systems which are widely used in small machines such as compact excavators.

Mechanical systems[edit]

There are also mechanical designs for continuously variable transmissions and these also have the ability to multiply torque. They include the pendulum-based Constantinesco torque converter, the Lambert friction gearing disk drive transmission and the Variomatic with expanding pulleys and a belt drive.

Usage[edit]

• Automatic transmissions on automobiles, such as cars, buses, and on/off highway trucks.
• Forwarders and other heavy duty vehicles.
• Marine propulsion systems.
• Industrial power transmission such as conveyor drives, almost all modern forklifts, winches, drilling rigs, construction equipment, and railway locomotives.

Function[edit]

Theory of Operation[edit]

Torque converter equations of motion are dominated by Leonhard Euler's eighteenth century turbomachine equation:

${\displaystyle \tau =\sum \left[r\times \frac{d}{dt}\left(m\cdot v\right)\right]}$

The equation expands to include the fifth power of radius; as a result, torque converter properties are very dependent on the size of the device.

Torque converter elements[edit]

A fluid coupling is a two element drive that is incapable of multiplying torque, while a torque converter has at least one extra element—the stator—which alters the drive's characteristics during periods of high slippage, producing an increase in output torque.

In a torque converter there are at least three rotating elements: the impeller, which is mechanically driven by the prime mover; the turbine, which drives the load; and the stator, which is interposed between the impeller and turbine so that it can alter oil flow returning from the turbine to the impeller. The classic torque converter design dictates that the stator be prevented from rotating under any condition, hence the term stator. In practice, however, the stator is mounted on an overrunning clutch, which prevents the stator from counter-rotating with respect to the prime mover but allows forward rotation.

Modifications to the basic three element design have been periodically incorporated, especially in applications where higher than normal torque multiplication is required. Most commonly, these have taken the form of multiple turbines and stators, each set being designed to produce differing amounts of torque multiplication. For example, the BuickDynaflow automatic transmission was a non-shifting design and, under normal conditions, relied solely upon the converter to multiply torque. The Dynaflow used a five element converter to produce the wide range of torque multiplication needed to propel a heavy vehicle.

Although not strictly a part of classic torque converter design, many automotive converters include a lock-up clutch to improve cruising power transmission efficiency and reduce heat. The application of the clutch locks the turbine to the impeller, causing all power transmission to be mechanical, thus eliminating losses associated with fluid drive.

Operational phases[edit]

A torque converter has three stages of operation:

• Stall. The prime mover is applying power to the impeller but the turbine cannot rotate. For example, in an automobile, this stage of operation would occur when the driver has placed the transmission in gear but is preventing the vehicle from moving by continuing to apply the brakes. At stall, the torque converter can produce maximum torque multiplication if sufficient input power is applied (the resulting multiplication is called the stall ratio). The stall phase actually lasts for a brief period when the load (e.g., vehicle) initially starts to move, as there will be a very large difference between pump and turbine speed.
• Acceleration. The load is accelerating but there still is a relatively large difference between impeller and turbine speed. Under this condition, the converter will produce torque multiplication that is less than what could be achieved under stall conditions. The amount of multiplication will depend upon the actual difference between pump and turbine speed, as well as various other design factors.
• Coupling. The turbine has reached approximately 90 percent of the speed of the impeller. Torque multiplication has essentially ceased and the torque converter is behaving in a manner similar to a simple fluid coupling. In modern automotive applications, it is usually at this stage of operation where the lock-up clutch is applied, a procedure that tends to improve fuel efficiency.

The key to the torque converter's ability to multiply torque lies in the stator. In the classic fluid coupling design, periods of high slippage cause the fluid flow returning from the turbine to the impeller to oppose the direction of impeller rotation, leading to a significant loss of efficiency and the generation of considerable waste heat. Under the same condition in a torque converter, the returning fluid will be redirected by the stator so that it aids the rotation of the impeller, instead of impeding it. The result is that much of the energy in the returning fluid is recovered and added to the energy being applied to the impeller by the prime mover. This action causes a substantial increase in the mass of fluid being directed to the turbine, producing an increase in output torque. Since the returning fluid is initially traveling in a direction opposite to impeller rotation, the stator will likewise attempt to counter-rotate as it forces the fluid to change direction, an effect that is prevented by the one-way stator clutch.

Unlike the radially straight blades used in a plain fluid coupling, a torque converter's turbine and stator use angled and curved blades. The blade shape of the stator is what alters the path of the fluid, forcing it to coincide with the impeller rotation. The matching curve of the turbine blades helps to correctly direct the returning fluid to the stator so the latter can do its job. The shape of the blades is important as minor variations can result in significant changes to the converter's performance.

During the stall and acceleration phases, in which torque multiplication occurs, the stator remains stationary due to the action of its one-way clutch. However, as the torque converter approaches the coupling phase, the energy and volume of the fluid returning from the turbine will gradually decrease, causing pressure on the stator to likewise decrease. Once in the coupling phase, the returning fluid will reverse direction and now rotate in the direction of the impeller and turbine, an effect which will attempt to forward-rotate the stator. At this point, the stator clutch will release and the impeller, turbine and stator will all (more or less) turn as a unit.

Unavoidably, some of the fluid's kinetic energy will be lost due to friction and turbulence, causing the converter to generate waste heat (dissipated in many applications by water cooling). This effect, often referred to as pumping loss, will be most pronounced at or near stall conditions. In modern designs, the blade geometry minimizes oil velocity at low impeller speeds, which allows the turbine to be stalled for long periods with little danger of overheating (as when a vehicle with an automatic transmission is stopped at a traffic signal or in traffic congestion while still in gear).

Efficiency and torque multiplication[edit]

A torque converter cannot achieve 100 percent coupling efficiency. The classic three element torque converter has an efficiency curve that resembles ∩: zero efficiency at stall, generally increasing efficiency during the acceleration phase and low efficiency in the coupling phase. The loss of efficiency as the converter enters the coupling phase is a result of the turbulence and fluid flow interference generated by the stator, and as previously mentioned, is commonly overcome by mounting the stator on a one-way clutch.

Even with the benefit of the one-way stator clutch, a converter cannot achieve the same level of efficiency in the coupling phase as an equivalently sized fluid coupling. Some loss is due to the presence of the stator (even though rotating as part of the assembly), as it always generates some power-absorbing turbulence. Most of the loss, however, is caused by the curved and angled turbine blades, which do not absorb kinetic energy from the fluid mass as well as radially straight blades. Since the turbine blade geometry is a crucial factor in the converter's ability to multiply torque, trade-offs between torque multiplication and coupling efficiency are inevitable. In automotive applications, where steady improvements in fuel economy have been mandated by market forces and government edict, the nearly universal use of a lock-up clutch has helped to eliminate the converter from the efficiency equation during cruising operation.

The maximum amount of torque multiplication produced by a converter is highly dependent on the size and geometry of the turbine and stator blades, and is generated only when the converter is at or near the stall phase of operation. Typical stall torque multiplication ratios range from 1.8:1 to 2.5:1 for most automotive applications (although multi-element designs as used in the BuickDynaflow and ChevroletTurboglide could produce more). Specialized converters designed for industrial, rail, or heavy marine power transmission systems are capable of as much as 5.0:1 multiplication. Generally speaking, there is a trade-off between maximum torque multiplication and efficiency—high stall ratio converters tend to be relatively inefficient below the coupling speed, whereas low stall ratio converters tend to provide less possible torque multiplication.

The characteristics of the torque converter must be carefully matched to the torque curve of the power source and the intended application. Changing the blade geometry of the stator and/or turbine will change the torque-stall characteristics, as well as the overall efficiency of the unit. For example, drag racing automatic transmissions often use converters modified to produce high stall speeds to improve off-the-line torque, and to get into the power band of the engine more quickly. Highway vehicles generally use lower stall torque converters to limit heat production, and provide a more firm feeling to the vehicle's characteristics.

A design feature once found in some General Motors automatic transmissions was the variable-pitch stator, in which the blades' angle of attack could be varied in response to changes in engine speed and load. The effect of this was to vary the amount of torque multiplication produced by the converter. At the normal angle of attack, the stator caused the converter to produce a moderate amount of multiplication but with a higher level of efficiency. If the driver abruptly opened the throttle, a valve would switch the stator pitch to a different angle of attack, increasing torque multiplication at the expense of efficiency.

Some torque converters use multiple stators and/or multiple turbines to provide a wider range of torque multiplication. Such multiple-element converters are more common in industrial environments than in automotive transmissions, but automotive applications such as Buick's Triple Turbine Dynaflow and Chevrolet's Turboglide also existed. The Buick Dynaflow utilized the torque-multiplying characteristics of its planetary gear set in conjunction with the torque converter for low gear and bypassed the first turbine, using only the second turbine as vehicle speed increased. The unavoidable trade-off with this arrangement was low efficiency and eventually these transmissions were discontinued in favor of the more efficient three speed units with a conventional three element torque converter.It is also found that efficiency of torque converter is maximum at very low speeds.

Lock-up torque converters[edit]

What Torque Converter To Use

As described above, impelling losses within the torque converter reduce efficiency and generate waste heat. In modern automotive applications, this problem is commonly avoided by use of a lock-up clutch that physically links the impeller and turbine, effectively changing the converter into a purely mechanical coupling. The result is no slippage, and virtually no power loss.

The first automotive application of the lock-up principle was Packard's Ultramatic transmission, introduced in 1949, which locked up the converter at cruising speeds, unlocking when the throttle was floored for quick acceleration or as the vehicle slowed. This feature was also present in some Borg-Warner transmissions produced during the 1950s. It fell out of favor in subsequent years due to its extra complexity and cost. In the late 1970s lock-up clutches started to reappear in response to demands for improved fuel economy, and are now nearly universal in automotive applications.

Capacity and failure modes[edit]

As with a basic fluid coupling the theoretical torque capacity of a converter is proportional to ${\displaystyle r{N}^2{D}^5}$, where ${\displaystyle r}$ is the mass density of the fluid (kg/m³), ${\displaystyle N}$ is the impeller speed (rpm), and ${\displaystyle D}$ is the diameter(m).^[1] In practice, the maximum torque capacity is limited by the mechanical characteristics of the materials used in the converter's components, as well as the ability of the converter to dissipate heat (often through water cooling). As an aid to strength, reliability and economy of production, most automotive converter housings are of welded construction. Industrial units are usually assembled with bolted housings, a design feature that eases the process of inspection and repair, but adds to the cost of producing the converter.

In high performance, racing and heavy duty commercial converters, the pump and turbine may be further strengthened by a process called furnace brazing, in which molten brass is drawn into seams and joints to produce a stronger bond between the blades, hubs and annular ring(s). Because the furnace brazing process creates a small radius at the point where a blade meets with a hub or annular ring, a theoretical decrease in turbulence will occur, resulting in a corresponding increase in efficiency.

Overloading a converter can result in several failure modes, some of them potentially dangerous in nature:

• Overheating: Continuous high levels of slippage may overwhelm the converter's ability to dissipate heat, resulting in damage to the elastomerseals that retain fluid inside the converter. This will cause the unit to leak and eventually stop functioning due to lack of fluid.
• Stator clutch seizure: The inner and outer elements of the one-way stator clutch become permanently locked together, thus preventing the stator from rotating during the coupling phase. Most often, seizure is precipitated by severe loading and subsequent distortion of the clutch components. Eventually, galling of the mating parts occurs, which triggers seizure. A converter with a seized stator clutch will exhibit very poor efficiency during the coupling phase, and in a motor vehicle, fuel consumption will drastically increase. Converter overheating under such conditions will usually occur if continued operation is attempted.
• Stator clutch breakage: A very abrupt application of power can cause shock loading of the stator clutch, resulting in breakage. If this occurs, the stator will freely counter-rotate in the direction opposite to that of the pump and almost no power transmission will take place. In an automobile, the effect is similar to a severe case of transmission slippage and the vehicle is all but incapable of moving under its own power.
• Blade deformation and fragmentation: If subjected to abrupt loading or excessive heating of the converter, pump and/or turbine blades may be deformed, separated from their hubs and/or annular rings, or may break up into fragments. At the least, such a failure will result in a significant loss of efficiency, producing symptoms similar (although less pronounced) to those accompanying stator clutch failure. In extreme cases, catastrophic destruction of the converter will occur.
• Ballooning: Prolonged operation under excessive loading, very abrupt application of load, or operating a torque converter at very high RPM may cause the shape of the converter's housing to be physically distorted due to internal pressure and/or the stress imposed by inertia. Under extreme conditions, ballooning will cause the converter housing to rupture, resulting in the violent dispersal of hot oil and metal fragments over a wide area.

Manufacturers[edit]

Current[edit]

• Aisin AW, used in automobiles
• Allison Transmission, used in bus, refuse, fire, construction, distribution, military and specialty applications
• BorgWarner, used in automobiles
• Exedy, used in automobiles
• Isuzu, used in automobiles
• Jatco, used in automobiles
• LuK USA LLC, produces Torque Converters for Ford, GM, Allison Transmission, and Hyundai
• Subaru, used in automobiles
• Twin Disc, used in vehicle, marine and oilfield applications
• Valeo, produces Torque converter for Ford, GM, Mazda, Subaru
• Voith Turbo-Transmissions, used in many diesel locomotives and diesel multiple units
• ZF Friedrichshafen, automobiles, forestry machines, popular in city bus applications

Past[edit]

• Lysholm-Smith, named after its inventor, Alf Lysholm,^[2] produced by Leyland Motors and used in buses from 1933-9 and also some British Rail Derby Lightweight and Ulster Transport Authority diesel multiple units
• Mekydro,^[3] used in British Rail Class 35Hymek locomotives.
• Packard, used in the Ultramatic automobile transmission system
• Rolls-Royce (Twin Disc), used in some British United Traction diesel multiple units
• Vickers-Coates^[4]

See also[edit]

References[edit]

1. ^Hydrodynamic couplings and converters. Automotive Handbook (3rd ed.). Robert Bosch. 1993. p. 539. ISBN0-8376-0330-7.
2. ^'Espacenet - Original document'. Worldwide.espacenet.com. 1933-03-07. Retrieved 2014-07-21.
3. ^'Archived copy'. Archived from the original on 2010-03-02. Retrieved 2009-10-31.CS1 maint: archived copy as title (link)
4. ^[1]

External links[edit]

Automatic Transmission Torque Converters

Ever wonder what a torque converter does?

Torque Converter Automatic

The torque converter transfers power from the engine to the transmission.

Without a torque converter, your automatic transmission won’t work.
Cars with automatic transmissions don’t have clutches, so they need a way to let the engine keep running while the wheels and gears in the transmission come to a stop. Manual transmission cars use a clutch that disconnects the engine from the transmission. Automatic transmissions use a torque converter.

A torque converter is a coupling that relies on a fluid hydrodynamic to allow the engine to spin independently of the transmission.

When the engine is idling, such as at a stop light, the amount of torque going through the torque converter is small, but still enough to require some pressure on the brake pedal to stop the car from creeping. When you release the brake and step on the gas, the engine speeds up and pumps more fluid into the torque converter, causing more power (torque) to be transmitted to the wheels.

How does a torque converter work?

There are three main parts in a torque converter.

1. Impeller

The first part of the torque converter assembly is called the impeller, also known as the pump. It is filled with fluid and it spins with the engine crankshaft. The faster it spins, the more force is created as the fluid flows through it faster and harder.

2. Turbine

The impeller forces the fluid into an assembly of blades called the turbine. The turbine sits opposite the impeller and rotates as the fluid from the impeller hits its blades. As the fluid flows through the turbine, it is repeatedly transferred from the outer section to the inner section of the turbine, then returned to the impeller. This constant circulation of fluid from impeller into turbine, then back to impeller, creates a fluid “coupling.”

3. Stator

The stator reverses the fluid and sends it back to the impeller, thereby slowing the fluid. As the transmission fluid returns to the impeller to keep the cycle going is where the torque is created. At this point the fluid is flowing in a different direction than it was originally as it came out of the impeller. This is where the stator comes in. The stator is another series of fins located between the two turbines on the transmission shaft. Its blades are angled so that when the transmission fluid flows into them, it reverses direction and gets channeled back to the impeller. When the vehicle stops, the stator’s one-way “clutch” causes it to stop spinning, which breaks the hydrodynamic circuit.

Along with the impeller, turbine, and stator are three stages of operation.

1. Stall

The engine provides power to the impeller, but the impeller doesn’t rotate because the driver keeps pressure on the brake, such as when at a stop light. The vehicle does not move, but it does not stall.

2. Acceleration

Acceleration occurs when the driver takes his foot off the brake and steps on the gas pedal. The impeller starts rotating faster, and there is a large difference between the impeller and turbine speed. This creates torque, and the converter produces torque multiplication, which is necessary for acceleration.

3. Coupling

As the vehicle reaches cruising speed, the turbine rotates at about the same rate as the impeller, and torque buildup stops. At this stage the torque converter is just a fluid coupling. The automatic transmission uses what is called a lockup clutch to “lock” the turbine to the impeller. This eliminates power loss and keeps the car moving smoothly. Because the impeller is mounted to the torque converter housing, and the converter is connected to the engine, the impeller gets its power from the engine. The turbine is connected to the output shaft, which sends power to the transmission. This why you might experience shaking or shuddering when something goes wrong with the torque converter.

Transmission troubles could actually be the torque converter.

Torque converter problems can be misinterpreted as symptoms of a failing transmission.

Don’t be misled into thinking you need expensive repairs, or even a full transmission replacement.

An accurate Vehicle Courtesy Check by a trained, honest transmission technician will tell you what the problem is and what repairs you need. Sure, replacing the torque converter isn’t cheap, but it’s definitely less costly than a new transmission. Diagnosing the cause of a transmission issue isn’t easy. AAMCO Colorado’s local technicians can help. It might just be a fluid leak, or something else altogether – our transmission inspection and Vehicle Courtesy Check help us find the problems and recommend the right services.

Signs of a failing torque converter are much like that of a failing transmission. Here are some things to be aware of.

Shaking and Shuddering

If your car shakes and shudders, it might mean the lockup clutch is failing or needs adjustment. You’ll experience the car shaking at speeds around 35-45 miles per hour. It’s a problem you cannot miss. It feels like you’re driving on a grated dirt road with a lot of small ridges. A worn out lockup clutch can make the transition from acceleration to cruising speed uncomfortable, to say the least – and it’s a sign you need to have your transmission checked.

Overheating

If your car overheats regularly, it might be a sign the transmission fluid is low. Low fluid results in low pressure, which means the torque converter can’t do its job. Additionally, low fluid can cause the torque converter to malfunction. If the converter is overheating, it won’t be able to transfer power from the engine to the transmission. This results in poor acceleration and excessive wear and tear on the transmission.

Slipping

A damaged fin in the torque converter can cause faltering in the transmission as it shifts, or the transmission to totally slip out of gear. This is due to the engine torque not being converted into the hydraulic pressure the transmission needs to shift gears. Slipping can also be caused by too little or too much fluid in the transmission.

Increased Stall Speed

A malfunctioning or failing torque converter will cause the transmission take longer to engage with the engine. This results in high stall speeds. There is a way to test for this, but you must know your engine’s and torque converter’s speed specifications. It’s easier to just bring your car to AAMCO and let the experts diagnose it.

Strange sounds are always a sign of something troublesome…

Any weird sounds such as clicking, revving, clunking, or whining indicate possible problems with the torque converter – or the transmission. Whichever the case may be, you won’t know until you pay attention to those noises, take heed, and take your car to a qualified expert transmission technician.

Related: Maintaining a Healthy Transmission

Poor maintenance is a poor excuse for transmission problems.

Even a poorly built transmission will suffer from poor maintenance. Things such as wrong fluid types or incorrect amounts of fluid can cause a lot of damage to a transmission. Incorrect fluid levels usually result from a poor or nonexistent maintenance schedule, as well as ignorance of what is required to effectively maintain a car. If you do check the transmission fluid regularly, and have it changed or flushed according to the manufacturer’s recommended maintenance schedule, then you should not have much to worry about. If you check the fluid yourself, be aware of not only the levels, but the colors. Here’s a handy chart:

Neglecting to be aware of the simple things that can help or hinder your transmission will speed its demise.

AAMCO Colorado – Your Transmission Experts

Visit an AAMCO Colorado transmission repair and total car care center near you. When larger issues arise and you need transmission repair, rebuild, or replacement schedule an appointment before it’s too late.

Torque Converter Rebuilders Near Me

If you have questions about your car’s road readiness, or about car repair and maintenance topics, AAMCO Colorado can help. You can also go online and use the AAMCO Colorado Ask a Mechanic feature to submit your auto repair questions. They will be answered by a real AAMCO Colorado mechanic as soon as possible.