**Diagnosis of Chassis Abnormal Noises in Several Vehicles** Home > Bearing Knowledge > Diagnosis of Chassis Abnormal Noises in Several Vehicles *Created on 2018/5/16* var cpro_id = "u3440131";

Diagnosis of Chassis Abnormal Noises in Several Vehicles

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When diagnosing abnormal noises coming from the chassis of a vehicle, it's essential to follow a systematic approach. Begin by driving the car on a flat road for a while until the rear axle reaches normal operating temperature. Then, when an unusual noise is heard, note the speed at which it occurs. After parking, shift the transmission into neutral and slowly accelerate until the engine speed matches the one when the noise was first noticed. Repeat this process several times to determine if the noise can be reproduced or eliminated, helping to identify whether the issue lies with the engine or other components. Tire noise and rear axle noise behave differently depending on the road surface. Tire noise tends to persist regardless of speed, whereas rear axle noise is typically not noticeable at speeds below 48 km/h. When the car is moving or coasting, tire noise remains consistent, but rear axle noise varies. The difference between hub bearing noise and rear axle noise becomes apparent when the vehicle is coasting. The noise from the front wheel bearing remains constant, but applying slight brake pressure while maintaining speed can reduce the load on the wheel bearing, thus weakening the noise. This helps in identifying the source of the sound. At speeds above 48 km/h, rear axle bearing noise is usually rare unless there is severe damage. During coasting or in neutral, a damaged rear wheel bearing may produce a "long-halogen" or "shasha" type of sound. The differential gears and differential bearings often emit a sharp "squeaky" or "crackling" sound, which is rhythmic and changes with the vehicle's speed. The front bearing of the reducer cone gear produces more noise when the car is coasting, while the rear bearing is louder during normal driving. The noise from the differential bearing is generally a steady, sharp sound, but its rhythm is much smoother compared to that of the reducer cone gear bearing. During straight-line travel, the rear axle gear noise is usually minimal because the differential half shaft gear and planet gear have little relative motion. However, abnormal noises can occur due to poor gear smoothness, leading to wear. If the noise is present at various speeds, it might indicate a loose nut on the automatic gear. At low speeds, knocking noises from the rear axle are common, especially when accelerating or decelerating. These sounds are often distinct and irritating. To diagnose such issues, check the following: 1. Improper clearance between the differential half shaft gear journal and the differential housing. 2. Inappropriate fit between the differential cross shaft journal and the differential housing. 3. Incorrect backlash between the half shaft spline gear and the differential half shaft gear keyway. 4. Improper meshing clearance between the differential half shaft gear and the planetary gear. 5. Inappropriate gap in the differential cone gear and forced gear meshing. 6. Worn thrust washers. If the abnormal noise occurs while driving, it may be caused by improper gear meshing clearance, incorrect preloading of the differential bearing, or both. When the noise is resolved, it's necessary to disassemble the differential gear to check the meshing clearance of the reducer gear, the preload of the reducer cone gear bearing, and the contact marks on the reducer gear. --- **Related Bearing Knowledge** - Methods for locking two types of bearings and conditions for SKF bearing correction. - TIMKEN spherical roller bearing layout features and sliding bearing information. - "Motor and generator on SKF bearing" device and disassembly process. This article is linked to http:// Please indicate China Bearing Network http:// Previous: Disposal methods for scars in SKF bearing units. Next: Common causes and solutions for drive shaft problems.

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