A hydraulic system (1) for controlling rotation of a railroad car body (2), and presenting a motor pump assembly (8) connected to a hydraulic fluid tank (7) and to a supply line (14); a number of hydraulic actuators (3a, 3b, 4a, 4b) for exerting mechanical force on the body (2) to rotate it; a solenoid valve (26) for selectively connecting the hydraulic actuators (3a, 3b, 4a, 4b) to the supply line (14) and to a drain (29) in response to electric control signals; and a device (61) for depressurizing the actuators (3a, 3b, 4a, 4b) and disabling the system at the end of the duty period or in the event of an emergency. The device (61) presents two hydraulically driven, normally-open disabling valves (47) interposed between respective pairs of actuators (3a, 4a; 3b, 4b) and the drain (29), and presenting respective drive lines (59) connected to the supply line (14); and an electric distributor (46) for depressurizing the drive lines (59).