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To obtain the simplified formula of viscous rolling resistance in the roller-raceway contact of tapered roller bearings, full EHD analyses in line contacts have been carried out for a wide range of dimensionless EHD parameters and meniscus distances in the inlet region. The results show that the effects of G and W on the viscous rolling resistance under full flooded conditions are small. However, the effects of U, G and W are influenced by the meniscus distance. The formula for frictional torque taking into account the simplified formula has been compared to the frictional torque obtained from experiment.

To achieve high efficiency in rear axle differentials, the reduction in friction torque of the tapered roller bearings supporting the pinion was investigated. The effects of internal geometry, and oil flow within the bearing, on friction torque were clarified. The friction torque of a newly developed bearing optimized considering various performance characteristics was 70-75% lower than that of a conventional bearing. This is equivalent to a friction torque reduction of about 80% from that of a standard bearing. This is expected to have a remarkable effect on vehicle fuel efficiency.