Impact of tripod joint pressing load variation on drive shaft rattling in passenger car

In today’s fast changing and competitive automotive world, vehicle NVH plays an important role in customer’s perception of the brand. A silent cabin with lower noise levels is a desired attribute in a modern car. In such a scenario, abnormal noises arising because of manufacturing variations and tolerances of components can impact the brand image of any automotive company negatively. This paper presents an investigation into a noise issue arising from the right-hand (RH) drive shaft of an automotive vehicle while driving on rough roads at approximately 30 km/h. Various technical measurements, including rotational backlash and dimensional assessments, were conducted, all of which were found within specification. However, axial play between the tripod spline and the mid-shaft spline was identified during disassembly. Further analysis revealed that material localization was the only change point in the RH drive shaft manufacturing process. The fit interference between the tripod spline and the mid-shaft spline was higher due to lower initial pressing load, which was identified as the root cause of the noise. A corrective measure was proposed by revising the tripod pressing load and adjusting the mid-shaft spline dimensions to reduce axial play and eliminate the noise. In conclusion, this paper emphasizes the role of tolerances in drive shaft system and root cause analysis of noise generating because of the same. The results demonstrate the criticality of pressing load on tripod spline for refined NVH and in turn, better customer perception.