This paper presents the result of fatigue tests carried out with an ATF and two types of traction oil. Since the performance of these oils as working fluid is preferred, the performance as a lubricant is inferior. The pitting life is evaluated by the value of D computed by the surface roughness and EHL film thickness. The high traction coefficient causes the tooth surface temperature rise by frictional heat, and then the oil film thickness and pitting life are decreased. To evaluate the performance of these oils as lubricants, the tooth surface temperature at the pitting tests is measured and the EHL film thickness is calculated with it for computing the value of D precisely. All results of fatigue test with three types of oils are examined together and it is found out that they are evaluated by the value of D only. The experimental formula to estimate the pitting life is obtained. This procedure is useful to design the surface gear strength of the automotive ATs and CVTs.

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