A monitoring system for a gearbox having at least one rotational component having a design lifetime and at least one design parameter is disclosed. The monitoring system may include a first sensor configured to generate a first signal indicative of a speed associated with the at least one rotational component, a second sensor configured to generate a second signal indicative of a torque associated with the rotational component, and a controller electronically connected to the first and second sensors. The controller may be configured to determine a remaining lifetime of the at least one rotational component based on the design lifetime, the at least one design parameter, and the first and second signals over a period of operating time, and generate a maintenance signal based on the remaining lifetime.