Abstract: A transmission assembly having a first, a second, a third, and a fourth planetary gear set is disclosed. The transmission assembly further includes an input shaft which drives the sun gear of the first planetary gear set, a first member which connects the planet carrier of the third planetary gear set and the ring gear of the fourth planetary gear set, and a second member which connects the sun gear of the third planetary gear set to the sun gear of the fourth planetary gear set. The transmission assembly yet further includes a third member which connects the ring gear of the first planetary gear set to (i) the planet carrier of the second planetary gear set and (ii) the ring gear of the third planetary gear set. The transmission assembly still further includes a fourth member which connects the planet carrier of the first planetary gear set to the sun gear of the second planetary gear set and an output shaft driven the planet carrier of the fourth planetary set.

Abstract: A countershaft transmission includes an input shaft, a countershaft, an output shaft, first and second disc type directional clutches associated with the input shaft, and disc type speed clutches associated with the countershaft and output shaft to selectively connect a plurality of constantly meshing gears in preselected patterns to provide three forward speeds and three reverse speeds for a work vehicle such as a track-type tractor. The gears and clutches are functionally arranged in a forward and reverse mechanism serially connected to a three-speed mechanism and a speed reduction ratio change can be made to the speed mechanism without effecting the speed reduction ratio of the forward and reverse mechanism. Reverse speeds greater than 20% faster than the corresponding forward speeds are possible using a three-gear train in the forward and reverse mechanism. The gears, and the directional and speed clutches are arranged to provide a radially and longitudinally compact transmission.