What was found
DURING SHUT-DOWN, PILOTS REPORTED CLUNKING NOISE. UPON FURTHER INSPECTION, NOISE WAS LOCATED AT UPPER PULLEY SPRAG CLUTCH AREA. REMOVED UPPER PULLEY AND FOUND M/R TRANSMISSION INPUT PINION (PN:269A5103-51) WORN EXCESSIVELY DUE TO LOOSE AFT PINION NUT. PROBABLE CAUSE OF AFT PINION NUT LOOSENING IS SB DB-019 (CORROSION PROTECTION OF INPUT PINION SPLINES). POSSIBLE EXCESSIVE APPLICATION OF ZINC-CHROMATE PRIMER TO INPUT PINION CAUSED IMPROPER CLAMP-UP DURING TORQUING PROCEDURE. (K)