As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) VIBRATIONS AND A NOISE WAS DETECTED BY AN ENGINEER DURING SHUT DOWN. FURTHER INVESTIGATION REVEALED THE INPUT YOKE RETAINING NUT WAS LOOSE. THIS IN TURN DAMAGED THE INPUT SPLINES BEYOND LIMITS AND THE GEAR BOX WAS REPLACED. THE INPUT SEAL P /N C996-3 HAD BEEN REPLACED PRIOR AT 1082.8 TSO. WE HAVE CONCLUDED THE TORQUE OFTHE NUT WAS NOT CORRECT. TRAINING HAS SINCE BEEN CONDUCTED.