Vehicle NVH (Noise Vibration & Harshness) is of continued concern to customers in this increasingly competitive market and driveline NVH performance is a key factor in overall vehicle quality. A typical way to increase this quality is the use of axle end of line test stands that utilize NVH signal analysis methods to offer pass/fail criteria. In the manufacturing environment there are high costs associated with axle assemblies that are rejected due to the amount of time for NVH analysis to determine root cause for the failure. Of more interest to both product development and manufacturing activities is the ability to understand the root cause of the failures from the axle end of line test stand. This information can improve the manufacturing process by eliminating errors, streamlining re-build activities, aiding in product design improvements, and in turn reducing cost. This paper describes the activities used to identify specific bearing defects for rear axle application through signal analysis of end of line test stand data. Measurements of both nominal and intentionally mis-built (head, tail, & differential) bearings, with known defect characteristics, were used to develop the analysis techniques. Various bearing fault frequencies and their harmonics of the NVH signatures were used to identify the specific failure mode for each of the mis-built (head, tail, & differential) bearings, which included rolling element pass defects, and cage spin defects.
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