Evolution limited slip diff,  55/90 ramp type. The steeper 55 degree acceleration ramp reduces the percentage of torque biased to the wheel with most grip, making this unit less aggressive and more suitable for road use.If you ever need to take the diff apart you must take the pre-load off with a press and then the 3 screws will come out easily. You will have to remove some metal from gearbox and diff casings, but less than with the old Salisbury.