Abstract: A measurement tool for determining a position of a pinion gear in a differential assembly includes a mounting member configured to contact an end face of the pinion gear and an elongated arm member extending outwardly from the mounting member. The arm member has an arm portion configured to overlie one of the bearing seats of the differential assembly and an aperture formed in the arm member configured to receive a measurement gage therethrough. The measurement gage is used to measure a distance between a surface of the bearing seat and a reference surface of the arm member from which the position or “pinion depth” of pinion gear can be determined.