A mobile drill rig has a drill mast, a carriage mounted to the drill mast for vertical movement, and a vibratory drill head having a sine generator and a rotation mechanism for imparting vibration and rotation to a drill rod string. An elastomeric torsion coupler couples the rotation mechanism to the sine generator to transmit rotational force to the drill rod string while isolating vibrations of the sine generator from the rotation mechanism. Another coupler connects the drill head to the carriage in a manner that allows floating vertical movement of the drill head relative to the carriage while isolating vibrations of the sine generator from the carriage. Elastomeric bumpers limit the vertical movement of the drill head relative to the carriage. Elastomeric spacers located between the rotation mechanism and the sine generator handle the vertical loading and maintain the proper spacing between the sine generator and the rotation mechanism.