A drivable caster wheel assembly comprises a support socket defining a journal, a support frame with a post with a portion thereof positioned in the journal and being rotatable in the journal of the support socket about a substantially vertical axis. The support frame may include an arm mounted on the post. An axle is mounted on the arm. A wheel is mounted on the axle and is rotatable about a substantially horizontal axis. A hydraulic motor is mounted on the support frame and configured to rotate the wheel with respect to the support frame. A fluid transfer structure is configured to transfer fluid from a fluid power source on the mobile base when the support socket is mounted on the mobile base to the motor for driving the wheel while maintaining an ability of the support frame and wheel to rotate about the substantially vertical axis.