Abstract: A hydraulic drive to, for example, a wheeled excavator comprises two motors (4, 6) connectable to the input side of a gearbox (8) whereby each motor (4, 6) can apply a driving force to a load connected to the output side of the gearbox (8), one motor (6) being selectively disconnectable from the load independently of the other motor (4) by means of a clutch (10). A control system for effecting said disconnection comprises a hydraulic pump (20) drive n by the gearbox (8) to be rotated at a speed proportional to that of the other motor (4), pressure-sensing means (24) for detecting the pressure of fluid displaced by the pump (20), and control means (28) for achieving selective actuation of the clutch (10) such that, when the sensing means (24) detect a pressure associated with a predetermined speed of the other motor (4) at which the drive from the one motor (6) becomes redundant, the control means (28) operate to disconnect the one motor from the gearbox (8).