In a collaborative project, Flender Corporation, SKF, and the National Renewable Energy Laboratory (NREL) have instrumented a commercial drivetrain, installed it in a wind turbine at the National Wind Technology Center, and operated the turbine for more than a year. The gearbox was specifically instrumented to measure high-speed bearing loads, sliding, and the lubricant environment. Commercial SKF black-oxide coated cylindrical-roller bearings were modified by magnetizing one roller and inserting a metal pin in the cage next to it to measure roller and cage speed, respectively, with an inductive coil [16] and a proximity switch. In this report, these measurements are used to validate two different modeling approaches for bearing sliding - one analytical dynamic model and one multibody model. Once validated, these models can be used to evaluate the roller slip losses or cumulative frictional energy that are considered potential driving factors for wind turbine gearbox high-speed-shaft and high intermediate speed shaft bearing failures by white etching cracks.