A viscous LSD uses the fluid viscosity of a dilatant fluid inside a sealed housing to control output shaft speeds. When the fluid is exposed to shearing forces caused by the two axles spinning at different speeds, it thickens up, forcing both output shafts or axles to partially lock and spin at the same speed. Viscous diffs are the most civil and the softest of the three types tested, since they act more like a torque converter instead of using solid mechanical connections to create lock. In theory, it requires the least amount of maintenance, but when exposed to hard-driving conditions, the dilatant fluid has a tendency to break down and degrade from excessive heat, losing its slip-limiting capabilities. Because of its non-mechanical nature, it's also less effective in transferring power.