Abstract: A transfer case for a vehicle that includes a planetary gear assembly, a clutch pack assembly, and a band and drum assembly that provide an overdrive or underdrive and direct drive in combination with a vehicle transmission. In one embodiment, an input shaft drives an outer ring gear of the planetary gear assembly and is coupled to one set of discs of the clutch assembly. A carrier of the planetary gear assembly is coupled to a rear output shaft, where the carrier supports a plurality of pinion gears. A sun gear of the planetary gear assembly is coupled to another set of discs of the clutch assembly that are coupled to the drum. When the clutch assembly is engaged, the ring gear is coupled to the sun gear for direct drive and when the band is engaged, the pinion gears and the ring gear provide underdrive.

Abstract: Engagement characteristics of electromagnetic friction clutch pack assemblies disposed in, for example, motor vehicle transfer cases are improved, especially at the transition between static and dynamic friction modes, by superimposing a random noise signal on an otherwise smooth analog or stepped digital signal. The controller and driver for the clutch includes a random noise (signal) generator having an output which is superimposed on the controller output generated in response to signals from various sensors disposed on the vehicle. When the controller inputs cause clutch engagement in accordance with the controller software, an engagement signal comprising both a drive portion and a smaller random noise portion is supplied to the electromagnetic clutch operator. Improved, less perceptible clutch engagement action is thereby achieved.