Abstract: A drilling rig includes a mast base and a mast having a structural frame extending from the mast base. The structural frame includes a first track extending along the length of the structural frame and a second track extending along the length of the structural frame spaced from and parallel to the first track. The drilling rig also includes a top drive carriage assembly having at least one sprocket arrangement operatively engaged with one of the first track and the second track. The first track and the second track each include a plurality of bushings equally spaced apart and attached to spaced apart track plates. The at least one sprocket arrangement has a plurality of teeth configured to operatively engage the plurality of bushings such that the top drive carriage assembly moves along the length of the structural frame of the mast.