A rotary mixer can include a frame, a rotor attached to the frame, four wheels attached to the frame for moving the rotary mixer, and a drive system for driving the four wheels, the drive system can include four independent hydrostatic drive loops, each of the independent hydrostatic drive loops associated with one of the wheels such that each one of the independent hydrostatic drive loops independently drives one of the four wheels; wherein the drive system includes a pressure balance mode of operation for relatively good traction ground or road conditions, and a wheel speed synchronization mode of operation for relatively poor traction ground or road conditions.