A method of calibrating a hydraulically operated clutch in a continuously variable transmission, characterized by steps of: filling the clutch in a like manner as for a shift, using a control signal having a predetermined test value for achieving a test pressure in the clutch; while the clutch is filled, determining a resulting change in a pressure difference in a hydrostatic power unit of the transmission, and: if the resulting change in the pressure difference in the hydrostatic power unit is more than a first predetermined value, then emptying the clutch and refilling the clutch, using a control signal having a different predetermined test value for achieving a test pressure in the clutch less than the previous test pressure; and if the resulting change in the pressure difference in the hydrostatic power unit is less than a second predetermined value, then emptying the clutch and refilling the clutch using a control signal having a different predetermined test value for achieving a test pressure in the clutch greater than the previous test pressure; and if the resulting change in the pressure difference in the hydrostatic power unit is between the first predetermined value and the second predetermined value, then recording the control signal value used to achieve the resulting change as a calibration value. filling the clutch in a like manner as for a shift, using a control signal having a predetermined test value for achieving a test pressure in the clutch; while the clutch is filled, determining a resulting change in a pressure difference in a hydrostatic power unit of the transmission, and: if the resulting change in the pressure difference in the hydrostatic power unit is more than a first predetermined value, then emptying the clutch and refilling the clutch, using a control signal having a different predetermined test value for achieving a test pressure in the clutch less than the previous test pressure; and if the resulting change in the pressure difference in the hydrostatic power unit is less than a second predetermined value, then emptying the clutch and refilling the clutch using a control signal having a different predetermined test value for achieving a test pressure in the clutch greater than the previous test pressure; and if the resulting change in the pressure difference in the hydrostatic power unit is between the first predetermined value and the second predetermined value, then recording the control signal value used to achieve the resulting change as a calibration value. if the resulting change in the pressure difference in the hydrostatic power unit is more than a first predetermined value, then emptying the clutch and refilling the clutch, using a control signal having a different predetermined test value for achieving a test pressure in the clutch less than the previous test pressure; and if the resulting change in the pressure difference in the hydrostatic power unit is less than a second predetermined value, then emptying the clutch and refilling the clutch using a control signal having a different predetermined test value for achieving a test pressure in the clutch greater than the previous test pressure; and if the resulting change in the pressure difference in the hydrostatic power unit is between the first predetermined value and the second predetermined value, then recording the control signal value used to achieve the resulting change as a calibration value.