Complete power train assemblies are durability tested in the laboratory by applying real-time, field-recorded axle loads with an electrohydraulic servo system. Transmission shifting is servo-controlled, permitting testing with power shift and power shift-torque converter type transmissions. The load-control system permits selecting any duty cycle or combination of duty cycles for the laboratory loading. Computer analysis of field and laboratory load data gives a damage rate comparison and component life predictions. A general description of test objectives, equipment, and operation, as well as examples of test results and data comparisons, are given.