As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OUTPUT SHAFT SPLINES ARE RUSTED, WORN AND ONE SPLINE IS CRACKED TOWARDS INBOARD SIDE. THIS IS THE FIRST TIME THE TAIL ROTOR ASSEMBLY WAS REMOVED SINCE RECEIVING THE AIRCRAFT NEW FROM BELL HELICOPTER. REPLACE GEARBOX ASSEMBLY WITH EXCHANGE UNIT.