Abstract: The effect of the content of butyl triphenyl thiophosphate (IR 232) on the anti-shudder performance of the automatic transmission fluid (ATF) was evaluated by the disc-on-disc tribo-test-rig (WAZAU). In view of the deficiency of the friction coefficient-velocity (μ-v) curve analysis method JASO M349 standard, the friction coefficient-friction endurance time (μ-t) curve analysis method was developed. The results showed that IR 232 had a great effect on the anti-shudder performance of ATF. Although the optimal range of IR 232 addition could be determined by using JASO standard μ-v curve analysis method, the exact time of anti-shudder performance failure could not be determined accurately. By using the method of μ-t, the precise time when ATF lost its anti-shudder performance could be accurately determined. Among the samples ATF A~F with different dosage of IR 232, ATF C showed the best anti-shudder performance and begun to lose anti-shudder performance at 65.7 h after the durability test, which indicated that the optimal dosage of IR 232 was 0.3%.

Key words: butyl triphenyl thiophosphate, the disc-on-disc tribo-test-rig, automatic transmission fluid, anti-shudder performance