The overrunning clutch is a crucial component of the planetary gearbox assembly, but domestically produced overrunning clutches are of inconsistent quality, with a lifespan of approximately 3000 hours. As market demand increases and loader tonnage grows, users demand higher service life from the overrunning clutch. It's common for overrunning clutches to fail in less than 2000 hours, damaging the reputation of loader manufacturers. Replacing an overrunning clutch is extremely troublesome, costing at least 2500 yuan, often delaying construction and causing unnecessary losses for users. Currently, domestic loaders commonly use two types of gearbox assemblies: planetary hydraulic-mechanical power shift gearboxes and fixed-shaft hydraulic-mechanical power shift gearboxes. We will mainly discuss planetary hydraulic-mechanical power shift gearboxes here. The biggest advantage of planetary hydraulic-mechanical power shift gearboxes is that the loader only needs two forward gears and one reverse gear to achieve all gear shifting functions (loading, driving, and reversing), giving the loader a strong ability to automatically adapt to external resistance. When the loader requires high forward and reverse speeds under normal conditions, the overrunning clutch automatically disengages, allowing the secondary turbine to operate independently. The power output from the secondary turbine is transmitted to each gear via the secondary output gear and the intermediate input shaft, enabling the loader to change gears and quickly transfer materials. When external resistance suddenly increases during loading operations, such as when encountering large materials, the overrunning clutch, in conjunction with the dual-turbine torque converter, automatically reduces speed and increases torque, providing sufficient power to the wheels for normal loading. When the loading resistance is extremely high, the overrunning clutch's structural characteristics become even more apparent. At this point, the overrunning clutch automatically enters a fully engaged state, where the outer ring gear, inner ring cam, and intermediate input shaft form a rigid body. The first and second stage turbines of the torque converter operate simultaneously, transmitting all generated torque to the overrunning clutch. The outer ring gear and intermediate input shaft simultaneously transmit power to the gearbox. Wheel slippage, commonly referred to as "stall," frequently occurs in loaders. This is achieved by the overrunning clutch utilizing the characteristics of a dual-turbo torque converter. Driven by the high-speed rotation of the engine, the torque converter pump impeller operates at zero speed, resulting in maximum torque output and maximum wheel-side driving force. A typical 50-ton loader can generate over 13 tons of thrust. The overrunning clutch in a planetary gearbox utilizes its unidirectional clutch action, combined with the external characteristics of the torque converter, to achieve this automatic adaptation to external working conditions. See the hydraulic torque converter characteristic diagram and the overrunning clutch working diagram. The external characteristic diagram of the hydraulic torque converter shows that the torque is at its maximum when the turbine speed is zero. Currently, there are two types of overrunning clutches used in China: cage-type and pin-type. Each type has its advantages and disadvantages. The cage-type overrunning clutch has a simpler structure, but its synchronicity is affected by the indexing accuracy of the cage, and the cage is prone to stress concentration, leading to premature fracture and ultimately, overrunning clutch failure. The top-pin type overrunning clutch has a slightly more complex structure, but the top pin is prone to cylinder effect. During frequent clutch engagement and disengagement, the rollers constantly impact the top pin, preventing oil from draining from the top pin hole in time, causing damage to the top pin end and leading to premature clutch failure. It's also important to note that the top pin's position should be designed so that its axis passes through the roller's axis when the clutch is in the wedged state. The inner ring cam of the overrunning clutch is a sensitive element. Because the contact point between the inner ring cam and the roller is a plane, although the surface hardness is 60 HRC, the considerable wedging force during frequent clutch engagement and disengagement will eventually cause it to develop an arc-shaped indentation from the rollers. Therefore, improving its wedge angle is essential. The contact surface between the outer ring gear and the roller, being an annular groove, often makes it difficult to achieve the required carburized layer concentration. A shallow carburized layer will accelerate wear and cause premature overrunning clutch failure. To improve the lifespan of the overrunning clutch in a transmission, we must clearly analyze the key factors affecting its lifespan and pay attention to these aspects during design, manufacturing, and assembly. With these efforts, we believe that the lifespan of the overrunning clutch can be effectively improved.