Abstract: An apparatus and a method for checking differential gear assemblies during manufacture positions each gear assembly mounted in a differential housing in a tray. The differential housing is oriented by prelocators and lifted into engagement with a bottom surface of a bed plate. Proximity switches mounted in the bed plate generate a position signal which actuates a compound slide to engage a brake with an output of the gear assembly. When the brake has been applied, a drive motor is actuated and moved into engagement with an input of the gear assembly to verify lockup. The motor is increased in speed, the brake is released after a predetermined time and the gear ratio of the gear assembly is determined during revolutions of free wheeling. The steps are replaced for a reverse direction of rotation of the motor and then the motor is run at low torque to sense torque to rotate and first resistance for calculating backlash.