Drive system for a motor vehicle with an adjustable constant pumping device

The propulsion system (1) has a hydrostatic drive device (10) for driving a vehicle axle (A1). A drive shaft (16) is set for driving another vehicle axle (A2). A pump unit (11) is connected with the hydrostatic drive device through a closed hydraulic circuit (K). The pump unit is provided with an adjusting device (12). The adjusting device is provided for manually adjusting the type-conditional delivery volume of the pump unit.