What Torque Converters Are

Torque converters are elements of vehicle transmission systems used in automatic gearboxes to help fulfill the role of the clutch in manual transmissions. As most forklifts out there use an automatic transmission system for higher operational comfort and usability, all of them use a torque converter to connect the engine/motor to the driven axle. The torque converter is something very similar (operation-wise) to the continuously variable transmission systems that are used in many modern car models nowadays since they allow a variable torque multiplication based on the specific user requirements. As a mechanical component, it is a kind of fluid coupling that bases its operation on the flow of a hydraulic liquid otherwise called the “transmission fluid”.

The individual elements that constitute the torque converter include the prime mover which is directly connected to the driving shaft (engine/motor), the impeller (or pump) which is driven by the prime mover and helps transfer kinetic energy to create a rotational vortex on the fluid, the turbine which is the main load driver, and finally the stator which is positioned in between the aforementioned elements and intervenes in cases of high slippage altering the flow from the turbine to the impeller, keeping the operation of the converter efficient under all conditions. All of these elements are tightly sealed in a round shaped component that is relatively compact and adequately rigid. Torque converters are reliable and effective enough to be used in cars, large trucks and buses, marine propulsion units, industrial power transmission systems, forklifts, drilling rigs, locomotives, and various types of logging equipment.

How Torque Converters Work

Simply put, the harder the accelerator pedal is pressed the higher the engine/motor RPM will get, and so the more rotations will be induced to the prime mover. The basic practical meaning of this is that the deeper the gas pedal is, the more torque is transferred to the driven axle connected to the transmission. Even when an engine is idling but a gear has been engaged, a small amount of torque is passed through the hydraulic coupling of the torque converter, so the operator has to keep one foot on the brake pedal in order to stay still. When a vehicle accelerates, the impeller and the turbine tend to sync but their rotation speeds remain quite far from one another because of the phase difference. During this phase, the torque is multiplied as the engine is free to run at a higher speed than the transmission. At some point, the impeller and the turbine rotation speed will be almost the same (more than 90%), and this is the point where the coupling happens and the lock-up clutch is engaged to improve the fuel efficiency, connecting the driving with the driven shaft at a ratio of 1:1. It is important to note however that this is only possible for torque converters that feature an additional part called “torque converter clutch”.

There can never be a 100% coupling efficiency due to the fact that torque converters cannot be made perfect, not even at a theoretical design level. For example, when the converter enters the coupling phase there will be a fluid flow turbulence generated by the stator. Another example is the turbine’s blades that cannot possibly absorb 100% of the fluid’s kinetic energy because they are curved and angled which is needed in order to retain the ability for torque multiplication that is much needed during the stall and acceleration operational phases. However, modern manufacturers have achieved pretty high efficiency figures by designing their converters to be specifically optimized for a particular engine/motor, by using advanced fluid mechanics simulation software, and by using state of the art materials that are less prone to overheating, deformation, fragmentation, and breakage.

Pros and Cons of Torque Converters

Advantages

• Letting the engine run free from the transmission and thus allowing it to achieve way higher RPM values that it would be possible otherwise brings a whole set of benefits, including a more comfortable and gradual loading of the engine that results in better lifecycle potential and lower risk of wear for its components.

• The element of the torque multiplication that is useful during the acceleration can make a huge difference in the performance of a vehicle since it can multiply the torque that is generated by the engine or motor by up to three or even five times. This will be especially useful for when starting on ramps, when climbing uphill at load, etc.

• Forklift operators don’t have to worry about clutches, engine stalling, torque control, etc., as the torque converter is undertaking all of these tasks with success, so the operators are free to remain focused on the load handling and control which is way more critical.

• Once the turbine of a torque converter reaches enough rotation speed, its own mass is providing it with beneficial inertia, offering a kind of a flywheel effect that smooths out all actions when driving the vehicle.

• Manual transmission clutches tend to overheat quickly and thus wear out if they slip too much, but torque converters can slip with almost no wear at all for as long as needed since the slipping is achieved through a non-friction method.

• Torque converters are much easier to maintain than a CVT system for example, so they are more suitable for harsh industrial applications such as forklift trucks.

Disadvantages

• There is always some kind of energy waste, resulting in more fuel or electric power lost as heat in the torque converter assembly. Contrary to the popular belief that has automatic transmission cars to have worse gas mileage due to inefficient gear change configuration, the mere existence and utilization of the torque converter is the main reason for this.

• Torque converters are great and all until they break down. From turbine blade deformation of fragmentation due to imposure to excessively abrupt load, to housing leakage or deformation (ballooning), and stator clutch breakage. When you have many collaborating components the chances of something breaking down increase exponentially.

• The weight of the torque converter assembly is significant, and although this has its own advantage (flywheel effect), it remains a problem that concerns the total efficiency of a vehicle.

• Sometimes, when under load, torque converters may behave strangely. Examples include an unlocker that suddenly locks when under pressure, excessive unintended slipping that results in an engine stall, shudder during locking and unlocking, etc.

Lift Parts Warehouse and Torque Converters

At Lift Parts Warehouse, you will find the best prices in torque converters for forklift trucks, ready to get shipped on the day of the order, and free of additional shipping costs. All of our torque converters are genuine and brand new, stored with care, away from moisture, excessive cold or heat, and of course free of loads from other boxes. This ensures that your part will reach you in perfect condition, in its original and sealed package, and with all of the accompanying documents such as the test certifications and the manufacturer’s warranties. In the unfortunate case of a defective Toyota forklift part, we take the full responsibility to replace it with a working one in a timely manner and at no additional cost. Our expert parts specialists can help you select the right torque converter for your forklift, no matter how old or obsolete it may be. Give us a call or chat with us online now to get a special offer on torque converters.