What was found
INPUT SEAL ON HELICOPTER MAIN TRANSMISSION LEAKED OIL WHICH WASHED MAIN DRIVESHAFT COUPLING GREASE THROUGH SHAFT AND INTO ENG COMPARTMENT. GREASE WAS DISCOVERED ON DAILY INSP BY PILOT AND HELICOPTER WAS GROUNDED FOR FURTHER INSP. THERE WAS NO INDICATION OF OVERHEATING OF THE COUPLINGS (BY THE TEMP SPOTS), BUT MOST OF GREASE HAD BEEN WASHED OUT OF THE FRONT COUPLING, THROUGH SHAFT AND THROUGH REAR COUPLING. NORMALLY, IF GREASE LEAKS OUT OF THE COUPLING, USUALLY FROM A TORN BOOT, LIFE OF THE COUPLING IS VERY SHORT. DRIVESHAFT WAS SENT FOR OVERHAUL.