Tru-Lok is an electronically locking differential (1). The differential has four pinion gears, three pinion shafts and two side gears. On the back side of one side gear (2) is half of the dog clutch.The electric locking differential is serviced as an assembly.A 12 volt electromagnetic coil (3) on the differential is controlled by the Totally Integrated Power Module (TIPM). When the coil (3) is energized the dog clutch is engaged which locks the one side gear to the differential case. This action locks the axles and triggers a switch (4) in the differential housing which activates the Tru-Lok indicator light on the dash.