Drive train of a vehicle

The powertrain (1) has drive unit (3) that drives combustion engine (2) which drives work hydraulic system (4) and hydraulic pump (7). The engine driven hydraulic pump is used as pump and motor to perform sucking operation of pressure medium from container (9), and leads to hydraulic system guided delivery line (10). The check valves (30,31) are opened in directions of delivery line, and connecting line (26) guided by pressure medium reservoir (25) based on pressure in connecting line. A pressure relief valve (32) is assigned to delivery line between check valve (30) and reservoir.