What was found
(CAN) PILOT REPORTED A VIBRATION, ABNORMAL AND "SHIFTING" FELT IN HOVER AND DURING FLIGHT. A PRECAUTIONARY LANDING WAS CARRIED OUT. PILOTS OBSERVED THAT THE TRANSMISSION WAS RESTING ON "PIN BACK-UP MOUNTS". AN AME WAS DISPATCHED TO INSPECT THE ACFT, A FLIGHT TEST WAS CARRIED OUT TO CONFIRM THE MAIN ROTOR TRANSMISSION RESTRAINT CONDITION AND THE ACFT WAS ALLOWED TO RETURN TO BASE WITH A SPEED RESTRICTION OF 80 KNOTS VNE. DEBONDING BETWEEN INNER MEMBER AND OUTER MEMBER OF ASSY. THE PITCH RESTRAINT SPRING ASSY DID HAVE AN ASB 429-13-10 ON 29 APRIL 2013 ON A LIMITED QTY OF UNITS THAT WERE MFG WITH INADEQUATE ADHESIVE MIX RATIO BETWEEN THE TUBE AND THE HOUSING. THIS CONDITION MAY CAUSE A BOND LINE SEPERATION.