In order to improve the performance of a common differential, recent patents on various limited-slip differentials have been addressed. In this paper, another new automatic limited-slip differential is proposed. It could be locked or unlocked automatically according to the vehicle’s travelling condition. This function is realized by adding a set of locking and clutch mechanism to the common cone gear differential. To better understand its structure, the engagements of each component during working, are analyzed. At the same time, the torque distribution is discussed when a wheel slips on the low-µ muddy road. The analytic results show that torque distribution is associated with the ground adhesion condition when the differential’s structure is certain. Moreover, the larger additional torque could not exist even if the locking coefficient increases. The results could provide reference for the future development of limited-slip differential.