Abstract: The gearbox synchronizer wear failure process using CF-4 15w/40 lube oil was investigated on the self-developed WS2001 synchronizer oil adaptability test bench. The failure mechanism was studied by analysis of the shift-characteristic curve, friction factor curve and the SEM figures of friction pairs before and after test. The results indicate that the shift-displacement goes up with the number of shifts, which leads to synchronizer failure because the shift block wears aggravate, making it difficult to press the sleeve with the cone. During the shift process, new contact surface appears continually due to friction of pairs, leading to a stable friction torque and moderate changes in the friction coefficient. However, in this process the stable oil membrane with enough strength cannot be formed on the surface of the friction pairs, causing wear of friction pairs. The surface of the test pieces has a large wear, the visible wear surface and curled asperities appear on the copper slider, the surface of the cone show scratches, and the synchronizing ring is worn and peeled.

Key words: transmission oil, synchronizer, wear failure, friction mechanism