Abstract: Improved actuation assemblies are used with variable geometry turbochargers comprising a plurality of movable aerodynamic vanes attached to a movable unison ring that is coupled to an actuator. The actuation assembly includes a crank arm that is attached at a first end to the actuator, and at a second end to the unison ring. A first gear member is attached to the crank arm second end and includes teeth. The unison ring includes a second gear member attached thereto that also comprises teeth. The teeth of the first and second gear members are cooperatively engaged with one another. The second gear member is movably attached to the unison ring to maintain predetermined distance between the first and second gear members during operation of the turbocharger and related thermal movement of the unison ring.