As a precisely matched gear pair of the drive axle, the bevel gear set has a much longer service life than conventional wearing parts. However, long-term heavy load, off-road bumps and improper lubrication will cause irreversible damage. Many car owners and maintenance personnel tend to replace parts blindly only according to abnormal noise. In fact, they can accurately distinguish minor problems that can be adjusted and repaired from hardware damages that require replacement through multiple dimensions such as noise characteristics, driving status and disassembly details.

Judging the fault degree through driving abnormal noise is the most intuitive method. A intact bevel gear set produces uniform and weak noise during uniform-speed driving, turning and sliding. If the vehicle makes a continuous low hum during straight driving, and the noise changes obviously during acceleration and deceleration, it means the meshing working surface of the gear teeth is uniformly worn with excessive clearance. If intermittent clicking impact sound occurs when turning, it indicates tooth root fatigue and meshing dislocation. Such structural wear cannot be repaired by adjusting clearance, and the bevel gear set must be replaced with a new one.

The power transmission state of the vehicle is also an important judgment basis. When the bevel gear set suffers severe wear, broken teeth or tooth surface peeling, the vehicle will have delayed power and empty transmission during heavy-load climbing, accompanied by occasional stalling sense of instantaneous power disengagement. Different from excessive common clearance, the power attenuation caused by hardware damage cannot restore the original vehicle transmission efficiency no matter adjusting gaskets or optimizing lubrication, which is a mandatory replacement indicator.

Disassembly inspection is the core standard to judge whether the bevel gear set is scrapped. After disassembling the drive axle, if there are metal scratches, large-area pitting, surface peeling, fine cracks on the tooth surface, or burrs, defects and irregular wear on the tooth top, it means the precision matching accuracy of the gear is completely invalid. The bevel gear set is factory precision-matched accessories. It is forbidden to replace a single gear separately. As long as either the driving gear or the driven gear has structural damage, the whole set must be replaced to avoid severe rear axle faults caused by mismatched meshing of old and new gears.

In addition, bevel gear sets that have experienced long-term unrepaired rear axle oil leakage, emulsified gear oil due to water ingress, and long-term dry friction without oil are recommended for direct replacement even without obvious abnormal noise for the time being. Such harsh working conditions will cause latent metal fatigue inside the gears. Although it seems normal in the short term, sudden tooth breakage and rear axle locking are very likely to occur under heavy load or off-road conditions, bringing great driving safety hazards.

Slight clearance deviation that can be repaired by simple adjustment does not require replacement. However, if there are four situations including structural wear, tooth damage, abnormal power and latent fatigue aging, timely replacing the whole bevel gear set is the best way to ensure stable vehicle chassis and avoid driving faults.