Two-stage final drive

Abstract

A two-stage final drive selectively provides two gear ratios between a transmission output member and the final drive or differential in a vehicle driveline. The two-stage final drive utilizes a planetary gear arrangement having a plurality of stepped pinion gears meshing with an input sun gear and two selectively brakeable ring gears. The planet carrier is connected with the input to a differential gear arrangement. The stepped pinion planetary gear arrangement provides two underdrive ratios and has operatively connected to one of the reacting ring gears, a dual mode roller clutch which is selectively controlled to provide a path to ground in two directions when the transmission is conditioned for Park, Reverse or Neutral, and a path to ground in one direction during the operation of the transmission in the forward direction. The dual mode device will permit forward rotation of the low speed ring gear when the high speed ring gear is selected as the reaction member. The dual mode member permits a conventional parking brake arrangement to be utilized by the transmission. As an alternative to the dual mode device, a more conventional one-way device in combination with a selectively operable mechanical one-way brake arrangement can be utilized in the two-stage final drive.