Abstract: A drive axle assembly includes a supplemental brake force assembly that utilizes a variable viscosity fluid. The assembly includes a housing defining a cavity and a drive component mounted for rotation relative to the housing. Rotating plates are mounted for rotation with the drive component and a Theological fluid is enclosed within the housing to surround the rotating plates. A current source generates current within the fluid to vary the viscosity. At higher traveling speeds, no current is applied to the fluid so the viscosity of the fluid is low, which reduces drag against the rotating plate. However, when a braking even occurs, current is applied to the fluid to increase viscosity and generate a supplemental braking force. The assembly is preferably incorporated into a wet disc brake with a plurality of non-rotating plates positioned in an alternating dispersal between the rotating plates.