The forklift universal joint transmission is primarily used when the two shafts are not aligned, allowing power to be transferred between them as their relative positions change during forklift operation. It is commonly found in heavy-duty models like the CPCD50 and 5CQN, connecting the transmission to the drive axle and the engine to the oil pump. This system consists of components such as the universal joint fork and cross shaft assembly, and its main function is to transfer power from the transmission to the final reducer.
Due to the high torque, speed, and heavy workload it experiences, the design may seem simple, but the technical requirements are quite strict. Any failure in this system can lead to issues such as shaking, noise, disconnection, or even shaft breakage.
To ensure smooth operation, the universal joint should not be too tight, bolts must be fully secured, the assembly angle should be correct, and lubrication must be adequate. There should be no vibration or unusual noises during driving. Therefore, regular maintenance of the drive shaft is essential, and any problems must be addressed promptly.
During forklift operation, the drive shaft is subjected to high torque and impact loads while rotating at high speeds. Continuous vibrations and poor lubrication make it prone to wear, deformation, and damage, which can result in malfunctions, abnormal noises, and shaking. When starting the forklift, if the body trembles and you hear a "clunk" sound, or if you notice periodic noises while driving that increase with speed, it could indicate an issue. In severe cases, the cab may vibrate, and the driver might feel numbness in their hands while holding the steering wheel.
Common causes include loose or damaged cross shafts and needle bearings, loose fasteners, or a bent drive shaft. To diagnose these issues, check if the connecting screws are loose, manually shake the drive shaft to detect worn parts, and rotate the rear wheel frame to observe any vibration or noise. A dial gauge can also help identify any deformation in the drive shaft. Once the cause is identified, repairs should be made accordingly.
If the dynamic balance of the drive shaft is disrupted, additional dynamic loads caused by centrifugal force can lead to bending, resulting in vibration, noise, increased load, reduced efficiency, and accelerated part wear. Accidental impacts, improper handling during disassembly, or misalignment after repairs can also affect the balance of the drive shaft.
When maintaining the drive shaft, it's important to add grease to the cross bearing. To check for looseness, place the transmission in neutral, release the parking brake, and hold the drive shaft tube with both hands. Gently turn it left and right—there should be no noticeable play. If there is, disassemble and repair as needed.
Before repairing the drive shaft, clean all parts thoroughly, especially the cross shaft’s oil passages, journal, and needle bearings. Clean them with kerosene and blow dry with compressed air. Apply grease to the mating surfaces and replace any worn components. After installation, the universal joint should move smoothly without resistance or gaps.
In the case of the CPCD50 forklift, the drive shaft connects the gearbox to the drive axle. It includes a flange fork, universal joint, cross shaft, and bearing. The cross shaft has a lubricating cup that allows for oil injection and proper bearing lubrication. If excessive clearance occurs in the needle bearing, the drive shaft should be disassembled, and the cross shaft or needle bearing replaced based on the wear condition (always replacing in pairs). Lithium-based grease should be used for lubrication, and calcium-based greases should be avoided, as they can accelerate wear on the bearings or cross shaft.
Solenoid Switch/Switching Valve (Normally Closed)
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