152 whereas line 146 communicates with passage 132c via a valve 154 and line 156 a hydraulic line 158 extends from passage 134c to the reservoir 152 the transmission is disengaged drive removed from output shaft 122c when the valve 154 is shifted to a position communicating line 156 with reservoir 152 thereby removing the hydraulic motor 140 from the hydraulic system and rendering the pinion gears 36c and 38c freely rotatable as in fig3 declutched condition the differential with axle speed control of fig1 may be advantageously utilized to steer a tracked vehicle as previously discussed when the input shaft 40 is in motion the direction of fluid flow in the hydraulic lines 72 and 74 as governed by the position of the valve 80 determines which axle or output shaft 22 or 24 has the highest speed the volume of fluid flow determines the speed difference between the two axles and therefore the rate at which the turn is executed when the input shaft 40 is stopped as would occur with the drive disengaged the output shafts 22 and 24 will turn in opposite directions as governed by the direction of fluid flow in the lines 72 and 74 again the volume of fluid flow will determine the speed difference between shafts 22 and 24 this enables a tracked vehicle.