Abstract: The gear consists of a four-shaft epicyclic gear, of which one shaft forms the input shaft which is in connection via an infinitely variable hydrostatic gear with the second shaft and of which the two remaining shafts represent connecting shafts which, in an extreme position of the hydrostatic gear, have the same speeds and behave during adjustment of the hydrostatic gear into the other extreme position in such a way that one becomes constantly slower and the other constantly faster, and which alternately act on the output shaft via gears of a gear group with following group shiftings. What is special is that the group shiftings make possible a multiple utilization of the gears of the gear group and that preparatory shifts for changing the group shifting provide the synchronization of idling gear parts, and that each gear change itself takes place at synchronous speeds, free from load and without tractive force interruption.

Abstract: A drive system includes a vehicle propulsion drive having a speed change gear box which drives tracks through a pair of planetary gears and a steering drive having a pair of variable hydrostatic drives. The hydrostatic drives engage a neutral shaft which superimposes rotation on the planetary gears to provide steering control for the tracks. The neutral shaft is separable into two segments. A differental reversing gear may be employed to selectively couple the neutral shaft segments. When the vehicle travels at high speed, the neutral shaft segments are coupled for unitary rotation. At low vehicle speeds, the propulsion drive is blocked and the neutral shaft segments are uncoupled so that both propulsion and steering are provided through the hydrostatic drives.