Manual displacement control device (MDC) for hydraulic units has an input shaft mounted rotatably about an input shaft axis in an input shaft block. The input shaft protrudes from the input shaft block with a first end, onto which a rotating torque can be applied. The MDC further includes a control spool housed in a control housing, which is moveable by means of rotating the input shaft for controlling a servo pressure. The control device has positioning means for adjusting and fixing the lateral position of the input shaft with respect to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of a restoring force exerted on the input shaft. The hydraulic unit is adjustable to its neutral position by means of a servo spring bracket providing an end stop surface for a servo spring seat towards the displacement element. The servo spring bracket is variably fixable to the hydraulic unit housing in a manner so that the orientation of the end stop surface can be adjusted parallel to the neutral position of the displacement element.