Troubleshooting Common Problems with Drive Shafts

Damage, wear, deformation, and loss of dynamic balance in steering driveshaft components can cause vehicle driving malfunctions. These malfunctions primarily manifest as abnormal noises and vibrations, and in severe cases, can lead to damage of related components. When the car is in motion, a "clunking" sound may be emitted during starting or rapid acceleration, accompanied by a noticeable feeling of component looseness. If this is not due to looseness in the drive axle transmission gears, then it is clearly looseness in the driveshaft components. This is easy to check: after parking, manually rock the steering driveshaft from underneath the car and observe the loose areas. Loose areas are typically the universal joint cross bearing cups, flange yokes, and the spline shaft and spline sleeve of the telescopic assembly. Generally, the clearance between the crosshead journal and the bearing should not exceed 0.13 mm, and the engagement clearance between the telescopic spline shaft and spline sleeve should not be greater than 0.3 mm. Components exceeding these service limits should be repaired or replaced.

When the car is moving, a "humming" sound occurs in the chassis, and the sound becomes louder as the driving speed increases. This is generally due to wear and looseness of the universal joint cross shaft and bearing, wear of the driveshaft center bearing, damage to the center rubber support or loose hanger straps, or incorrect positioning of the hanger bracket.

Working principle of a universal joint

Constant Velocity Motion: Conditions for constant angular velocity transmission of the input shaft:

1) The universal joint forks at both ends of the transmission shaft are in the same plane;
2) The angle α1 between the two shafts of the first universal joint is equal to the angle α2 between the two shafts of the second universal joint.

Universal Joint: Because the drive axle moves relative to the transmission during driving, it is impossible to have α1 = α2 at any time. In practice, only approximate constant velocity transmission from the transmission to the drive axle can be achieved.

In the above transmission device, the larger the angle α between the shafts, the more uneven the rotation of the transmission shaft, the greater the additional alternating load generated, the more unfavorable it is for the service life of the components, and the lower the transmission efficiency. Therefore, the angles between these shafts should be minimized in the overall layout.

Mutual Cooperation: In the universal joint shaft matching, the rotation of one component (output shaft) around its own axis is driven by the rotation of another component (input shaft) around its axis.

A universal joint, also known as a U-joint, is a component that achieves variable-angle power transmission. It is used in locations where the transmission shaft axis needs to change direction. It is the "joint" component of the universal joint transmission device in the automotive drive system. The universal joint and transmission shaft are combined to form a universal joint transmission device.

The structure and function of the universal joint are somewhat like the joints in the human limbs. It allows the angle between the connected parts to change within a certain range. To meet the requirements of power transmission and adapt to the angle changes caused by steering and the up and down movement during vehicle operation, universal joints are commonly used to connect the drive axle, half-shaft, and wheel axle of front-wheel-drive vehicles. However, due to the limitation of the axial dimension and the relatively large required deflection angle, a single universal joint cannot make the instantaneous angular velocity of the output shaft equal to that of the input shaft, which easily causes vibration, accelerates component damage, and produces significant noise. Therefore, various constant-velocity universal joints are widely used. In front-wheel-drive vehicles, each half-shaft uses two constant-velocity universal joints. The universal joint closer to the transmission drive axle is the inner half-shaft universal joint, and the one closer to the axle is the outer half-shaft universal joint. In rear-wheel-drive vehicles, the engine, clutch, and transmission are installed as a unit on the frame, while the drive axle is connected to the frame via elastic suspension. There is a distance between the two, which needs to be connected. During vehicle operation, uneven road surfaces cause bouncing, load changes, or installation differences between the two assemblies, which can cause changes in the angle and distance between the transmission output shaft and the drive axle main reducer input shaft. Therefore, double universal joints are used in the universal joint transmission of rear-wheel-drive vehicles, meaning there is one universal joint at each end of the transmission shaft. Their function is to make the angles at both ends of the transmission shaft equal, thus ensuring that the instantaneous angular velocity of the output shaft and the input shaft are always equal.

The working principle of a universal joint

A universal joint, also known as a U-joint, is a mechanical device that allows for power transmission at varying angles. It's used in locations where the direction of the drive shaft needs to be changed and serves as the 'joint' component in a vehicle's universal drive system. A universal joint combined with a drive shaft is called a universal drive assembly. A universal drive assembly typically consists of a universal joint and a drive shaft, sometimes also including an intermediate support. It is mainly used in the following locations: 1- Universal joint; 2- Drive shaft; 3- Front drive shaft; 4- Intermediate support. In universal joint coupling, the rotation of one component (output shaft) around its own axis is driven by the rotation of another component, the universal joint (input shaft).

Universal joints can be classified into rigid universal joints and flexible universal joints based on whether they exhibit significant elasticity in the torsional direction. Rigid universal joints can be further categorized into three types: non-constant velocity universal joints (commonly the cross-axis type), near-constant velocity universal joints (such as double universal joints), and constant velocity universal joints (such as ball-type universal joints).

Precautions before using universal joint shafts

 1. If it is a universal joint shaft with an expandable spline pair, then during installation, the position of the spline sleeve should be checked to see if they match. If they do not match, it will cause impact during the operation of the universal joint shaft, thereby damaging it. Hebei Fengtuo Machinery Manufacturing Co., Ltd. is located in Daluzhen, Hebei, one of the top ten agricultural machinery parts trading markets in the country, enjoying a superior geographical location and convenient transportation.

2. The two ends of the universal joint shaft can, in principle, serve as active or driven ends. However, during installation, it must be ensured that they comply with the design requirements of the transmission system. In addition, it should be noted that the spline mating surfaces should be kept as far as possible from vibration and impact sources, and dirt or water should be prevented from entering the spline mating surfaces to avoid various problems.

3. Before installation, the flange mating surfaces must be cleaned. If there is anti-rust grease on them, it should be cleaned off in time. Furthermore, any unfavorable factors on the mating surfaces should be eliminated to reduce friction.

4. The universal joint shaft should avoid long-term overload use and must be operated correctly to prevent damage.

5. The lubrication of the universal joint shaft should be carried out according to specified requirements, and regular maintenance should be performed, primarily checking the bearing raceway, the contact surface between the bearing end face and the baffle, and the spline pair mating surface, etc., to assess their wear condition and determine if replacement is needed.