A hydraulic servo-control of a servo-controlled gearbox comprising: a number of hydraulic actuators provided with respective chambers; a storing tank containing control fluid used by the hydraulic actuators at room pressure; a hydraulic accumulator comprising an outer housing provided with an axis; and a piston, which is arranged inside the outer housing, is sliding along the axis, and is adapted to define, inside the outer housing, a first variable-volume chamber for a gaseous material and a second variable-volume chamber for a control fluid under pressure; and limit stop means, which are arranged at an open end of the outer housing which serve as a lower limit stop element for the travel of the piston inside the outer housing itself; and an upper limit stop element (20*) which defines an upper limit stope element for the travel of the piston inside the outer housing; a motor pump, which draws the control fluid from the storing tank and feeds the control fluid under pressure to the hydraulic accumulator; and a number of solenoid valves, which are adapted to selectively connect the chambers of the hydraulic actuators to the storing tank and to the hydraulic accumulator; the servo-control is characterized in that it further comprises a pressure limiter inside the first variable-volume chamber; and in that the outer housing has the shape of a cup-shaped body and comprises an upper wall and a lateral cylindrical wall coaxial to the axis; the upper limit stop element (20*) serving as the pressure limiter inside the first variable-volume chamber and being provided at a closed end of the outer housing close to the upper wall as a shoulder coaxial to the axis obtained in an inner surface of the lateral cylindrical wall of the outer housing; the upper limit stop element (20*) being obtained at a height of the outer housing to keep the pressure value inside the first variable-volume chamber within a safety range between 55 and 135 bar in any condition so as to limit the speed and/or acceleration of the piston which impacts against the limit stop means in case a traumatic and large damage occur in the conduits downstream of the hydraulic accumulator generating a considerable depression. a number of hydraulic actuators provided with respective chambers; a storing tank containing control fluid used by the hydraulic actuators at room pressure; a hydraulic accumulator comprising an outer housing provided with an axis; and a piston, which is arranged inside the outer housing, is sliding along the axis, and is adapted to define, inside the outer housing, a first variable-volume chamber for a gaseous material and a second variable-volume chamber for a control fluid under pressure; and limit stop means, which are arranged at an open end of the outer housing which serve as a lower limit stop element for the travel of the piston inside the outer housing itself; and an upper limit stop element (20*) which defines an upper limit stope element for the travel of the piston inside the outer housing; a motor pump, which draws the control fluid from the storing tank and feeds the control fluid under pressure to the hydraulic accumulator; and a number of solenoid valves, which are adapted to selectively connect the chambers of the hydraulic actuators to the storing tank and to the hydraulic accumulator; the servo-control is characterized in that it further comprises a pressure limiter inside the first variable-volume chamber; and in that the outer housing has the shape of a cup-shaped body and comprises an upper wall and a lateral cylindrical wall coaxial to the axis; the upper limit stop element (20*) serving as the pressure limiter inside the first variable-volume chamber and being provided at a closed end of the outer housing close to the upper wall as a shoulder coaxial to the axis obtained in an inner surface of the lateral cylindrical wall of the outer housing; the upper limit stop element (20*) being obtained at a height of the outer housing to keep the pressure value inside the first variable-volume chamber within a safety range between 55 and 135 bar in any condition so as to limit the speed and/or acceleration of the piston which impacts against the limit stop means in case a traumatic and large damage occur in the conduits downstream of the hydraulic accumulator generating a considerable depression.