The present invention is adapted to provide a method for determining the torque of a driveshaft. In the preferred embodiment a drivetrain includes a front and a rear drivetrain. The drivetrain is also connected to an engine, torque converter, front and rear axle and a transmission. In one embodiment, the ability to determine the transmission output torque for an earth moving machine includes determining an output torque of the converter and a gear reduction of the engine, and then responsively determining the front and rear driveshaft torque in response to the converter output torque and the engine gear reduction. The driveshaft torque calculations may be performed while the earth moving machine is operating. The resulting front and rear driveshaft torque calculations may be used to determine an axle damage index, or axle life calculations.