An improved crown pulley assembly attached to an upper end of a vertical drilling rig derrick mast used in conjunction with an improved top drive assembly which is used within the drilling rig derrick for the drilling of a well, the improved crown pulley assembly having a crown frame supporting a plurality of pulleys with the top drive providing two sets of paired top drive pulleys, the pulleys suspending a single drive cable through the plurality of pulleys with an anchor end of the single drive cable affixed below the derrick and the winch end of the cable attached to a winch to raise and lower the improved top drive assembly within the drilling rig derrick.