A locking system for a narrow package differential with a locking collar, a ring gear and a side output gear is provided. The locking collar has at least one locking tab. The ring gear has at least one ring gear slot and an opening section in each ring gear slot. The at least one ring gear slot receives the at least one locking tab of the locking collar. The side output gear has at least one side gear slot. The side output gear is positioned such that the at least one side gear slot can be accessed through the opening section in the ring gear slot. The at least one locking tab of the locking collar in the ring gear slot is selectively received within the side output gear slot to selectively place the differential in a locking configuration.