just read a automotive text book in MPH, viscous LSD also uses clutch plate.
The difference between viscous and normal is that normal uses spring / cone spring or whatever physical, while viscous lets the clutches rubs the oil until hot then the oil thickens and starts to behave like very powerful glue and locks the clutch plates more and more towards the LSD casing, hence both sides starts to turn the same.
Special oil it is ...... cool.................. stuff.............