INTRODUCTION There are three kinds of switching elements used in automatic transmissions. Clutches may be dry or wet type friction clutches, where wet type clutches are most commonly used in automatic transmissions. One-Way Clutches (OWC) are also commonly used in automatic transmissions. Selectable OWCs (SOWC) are a new kind of switching elements in automatic transmission. SOWCs have numerous benefits over traditional friction clutches. In the low/reverse position they save space, reduce spin loss, reduce complexity, and reduces cost. In Hybrid transmissions SOWC provide significant improvement in fuel economy without the negatives associated with traditional friction clutch systems. This paper will attempt to discuss the benefits as well as the challenges of implementing SOWC. Clutches A “Clutch” is a device that is used to mechanically connect and disconnect machine elements. A clutch either transfers torque in both clockwise (CW) and counter-clockwise (CCW) direction, or neither direction. Also, it is a device that requires active control. Clutches have the ability to slip. During their transition from open and not transferring torque to clamped and transferring torque, the clamp load can be modulated to force the clutch to transfer only part of the applied torque. This can be a blessing when trying to achieve a smooth shift. It can also be a curse as the friction plate(s) wear and lose their ability to transfer torque. If slip is not properly managed heat can buildup and damage the friction material. Proper level of slip is very important to smooth shifts in automobiles. Figure 1. Cutaway of automatic transmission showing 4 wet friction clutches. An automotive manual transmission has a clutch between the engine and transmission that is typically pedal-operated by the vehicle driver. Depress the pedal and the engine and transmission are disconnected, so engine power cannot get to the drive wheels. When the driver takes their foot off the pedal the engine and transmission are connected so engine power is applied to the drive wheels. In this example, if the pedal is released poorly, the vehicle may lurch, jerk, spin the tires, or stall the engine. Inexperienced drivers may struggle to learn how to coordinate all that goes into making a smooth engagement. One-Way Clutches One-Way Clutches (OWC) are devices used to mechanically connect and disconnect machine elements. An OWC transfers torque in one direction (for instance, only CW) and does not transfer torque in the other direction (for instance, CCW). An OWC does not require or have active control. One way clutches are not typically designed to slip, they transition from freewheeling to lockup rapidly. OWC can be Friction type or Ratchet type.Development and Challenges of Electrically Selectable One-Way Clutches Norman J. Bird, Raunak Bindra, and Jacob Klaser Ford Motor Company ABSTRACT This paper discusses new developments in the field of one-way clutches (OWC). These recent developments involve “Selectable OWC (SOWC)” actuating both hydraulically as well as electrically. The primary focus of this paper is a low-current consuming Electrical SOWC (eSOWC) used in hybrid transmission being designed and developed at Ford Motor Company. Other SOWCs currently being utilized across different applications at Ford are also discussed. Clutching devices represent significant cost, weight, size and drag-loss in automatic transmissions. However, implementation of SOWCs offers the potential to reduce transmission cost, size, weight, and spin loss; eSOWCs may also improve shift quality, reduce shift times, improve shift consistency and reduce OWC-related NVH. In Hybrid applications the electric motor(s) and SOWC create a system that is analogous to a manual transmission synchronizer. Similarly, in automatic transmissions SOWC are analogous to pump-solenoid-valve-friction-clutch system. In conclusion, this paper is intended to educate the reader on the development challenges and be