Tcabot113 Riff Raff
Things inside of a transmission are rarely without all lube even if jets are clogged due to misting of all of the oil flowing around. I attended an AHS meeting where Bell Helicopter showed a HUMS trace from a 412 where the tail rotor output quill of the main transmission had restricted lube to the bearings due to "cork" in the oil port (not known until inspected). The vibration of the quill was monitored for one year before the decision was made to overhaul it where the cork was found. The bearings had sufficient damage to cause vibration alerts, but no chip indications.
So are you saying there was a 12 month knowledge with the HUMS regarding unexplained vibration on quill
