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In automotive manual transmission gearboxes, the synchronizer rings play a vital role in gear shift operations. The efficiency of the synchronizer ring depends upon the frictional surface geometry. The critical parameter is the synchronizer ring frictional surface circularity. The circularity deviation causes higher synchronizer ring wear and poor cone torque generation. With the current manufacturing methods and the thickness of the synchronizer ring, circularity improvement is a challenge. The synchronizer ring thread turned part is lapped to improve the circularity. Reduction in circularity can be improved by optimizing the lapping operation. In this work, an optimal lapping condition was developed using statistical methods. Taguchi DOE was used to analyze the different parameter combinations along with the noise parameter – different ranges of circularity variation in turning operation. This helps to find the best lapping parameter settings to improve the reduction in circularity.

The brass synchronizers are not resistant to abusive conditions of gearbox operations, but they are very durable and cheap when used on their favorable material property working limit. The main failure which can occur in the gearbox due to the synchronizer is crash noise. During gear shifting the gear crash will create high discomfort for the driver and must apply high force to change the gears. The main factors which contribute to the crash phenomenon are the insufficient coefficient of friction, high drag in the system, and high wear rate of the synchronizer rings before the intended design life of the synchronizer. The brass synchronizers were tested on the SSP-180, ZF synchronizer test rig to know the effect of the synchronizer performance parameters like the coefficient of friction, sleeve force, slipping time as well as durability parameters like wear rate when the operating temperature of the oil is changed.