What Are the Symptoms of Driveshaft Vibration?
2 Answers
When starting the car or shifting gears during driving, there is a knocking sound from the driveshaft, which becomes more noticeable especially when driving at low speeds in high gear. If there is no abnormal noise from the driveshaft when starting the car but knocking sounds occur during driving, or if the noise persists throughout the entire driving process, it may indicate driveshaft vibration. Below are the causes of driveshaft torsional vibration: Driveshaft bending and eccentricity: After prolonged use, especially when driving on uneven roads, the front and rear wheels bounce up and down, causing the engine and driveshaft to undergo relative axial movement. This exerts axial forces and moments on the center support shaft, leading to bending and imbalance of the driveshaft, which results in vibration during rotation. Driveshaft imbalance: In addition to bending and twisting deformation, assembly errors exceeding limits, imprecise part dimensions, and wear and deformation during use can cause uneven mass distribution along the length of the driveshaft, leading to unbalanced force transmission. This creates additional bending moments during operation, not only causing impact noises in mating parts but also exacerbating the bending vibration of the driveshaft. Solutions for driveshaft vibration: Remove the left and right half-shafts and perform a balance test by running the driveshaft at high and medium throttle speeds in neutral. If no vibration is observed, the driveshaft is normal. Otherwise, conduct sectional tests to identify the vibrating part. Then, use a dial indicator to check the radial runout of the driveshaft to locate the eccentric position. Alternatively, attach weights of different masses to the opposite side of the eccentricity using hose clamps. Repeat the test multiple times to find the optimal balance position and appropriate weight. Finally, fix the balance weight by welding.
When driving an older car, I noticed that driveshaft vibration first appears at specific speeds, such as between 60 to 80 km/h, causing the entire body to shake. The steering wheel vibrates so much it numbs my hands, and the seats and floor hum loudly. The vibration worsens when accelerating and eases when decelerating, directly correlating with speed. In terms of noise, there's often a low-pitched hum or rattle coming from the chassis. If left unrepaired for a long time, the car may feel like it's pulling to one side, with unstable handling, especially noticeable during turns or on uneven roads. This causes additional wear on the tires and suspension, so I recommend immediately checking the universal joint or balance issues to avoid high-speed hazards. This experience is particularly common in older vehicles, and after parking, you might even feel looseness when touching the driveshaft.
