TRACKHOE HAD BLOWN AN ORING WHICH RESULTED IN THE NEED FOR ADDITIONAL HYD OIL. EE WAS REMOVING FILLER CAP ON TOP OF MACHINE WHEN HE TURNED AROUND TO DESCEND, LOST HIS BALANCE, MISSED THE HAND HOLD & LANDED ON CRAWLER TRACK BELOW. APPROX 3 FT DROP TO TRACK FROM ABOVE.