<p>An internal shift control mechanism for a motor vehicle gearbox comprises
- a fork member (4) for engaging and displacing a synchronizer sleeve (1) of the gearbox in an axial direction between a neutral position and at least one active position;
- a carriage (3) supporting the fork member (4), displaceably guided in the axial direction;
- a shifter axle (9) having an axis of rotation which extends transversally with respect to the displacement direction of the carriage andcarrying a shift arm (10) which engages a shift gate (6; 29) formed on said carriage (3). In the active position a tangent at a contact point between the shift arm (10) and the shift gate (6; 29) is perpendicular to a radius extending from the axis to the contact point.</p>
