EMPLOYEE WAS ATTEMPTING TO BACK THE DOZER UP SO THAT HE COULD CONNECT TO THE AIR TRACK DRILL IN ORDER TO MOVE IT TO ANOTHER LOCATION. INVESTIGATION LEADS US TO SUSPECT THAT THE TRANSMISSION LI NKAGE BROKE, CAUSING THE UNIT TO FREE WHEEL BACKWARDS. THE VICTIM JUMPED FROM THE DOZER JUST PRIOR TO IT GOING OVER THE HIGHWALL; HE SUSTAINED MINOR INJURY TO HIS RIBS.