Investigation of Synchronizer Ring Failure in a Commercial Vehicle Transmission

The commercial vehicles market is dominated by manual transmission, due to lower ownership cost. Generally, commercial vehicles are used in large numbers by the fleet owners. The transmission endurance life is very important to a vehicle owner. On the other hand, driver fatigue can be reduced with a smooth gear change process. The gear change process in a manual transmission is carried out with the help of the synchronizer pack. The crucial function of a synchronizer pack in an automotive transmission is to match the speed of the target gear for smooth gear shifting. In a transmission, the loose and the weakest part is the synchronizer ring. The failure of the synchronizer affects smooth gear shifting and it also affects the endurance life of the transmission. The synchronizer ring can fail due to poor structural strength, synchronizer liner wear, synchronizer liner burning, etc. The synchronizer liner burning is very difficult to analyze since the liner wear pattern is very uneven and the liner surfaces are burnt. The investigation has to be carried out in a multidirectional way to find the root cause of this type of failure. This paper focuses on the failure investigation of the synchronizer ring due to burning.