a limited slip differential is disclosed which includes a first rotary element , a second rotary element , and hydraulic means including a plurality of reciprocal pistons in slidable engagement with internal cam surface means of the first rotary element . the hydraulic means include an accumulator and fluid passage means in fluid communication with the accumulator and each of pressure chambers defined by the pistons . a pressure relief valve is provided in the accumulator chamber to prevent excessive increase in hydraulic fluid pressure in the hydraulic means .