A B737-300 IMMEDIATELY AFTER TKOF DECLARED AN EMER AND RETURNED TO THE FIELD DUE TO LOSS OF ENG OIL PRESSURE AND QUANTITY CAUSED BY ACCESSORY GEARBOX DRIVE PAD COVER NOT REINSTALLED AFTER BORESCOPE INSPECTION.

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I WAS ASSIGNED TO ACFT XXX WITH A SVC CHK AND A BORESCOPE. THE ACFT REQUIRED 3 MAIN TIRE CHANGES. MY LEAD TOLD ME TO OPEN THE ENG AND THEN WORK THE TIRE CHANGES AS THERE WAS SOME CONFUSION AS TO WHICH PLUGS WERE TO BE REMOVED FROM THE ENG. QUALITY CTL WAS TO COME BY AND INFORM US OF WHAT THEY NEEDED. MY LEAD TOLD ME HE WOULD HAVE ANOTHER MECH DO THE REMOVAL OF THE ENG PLUGS; AS I WAS BUSY WITH TIRES AND THE SVC CHK. OUR NITROGEN CART WAS OTS AND I HAD TO JACK THE ACFT BY HAND. AFTER INSTALLING THE NEW TIRES I FOUND THAT 2 WERE LOW AND I HAD TO GO IN SEARCH OF ANOTHER NITROGEN BOTTLE AND REGULATOR. WHEN I FINALLY COMPLETED THE TIRE CHANGES AND THE SVC CHK; MY LEAD DROPPED BY TO TELL ME THAT INSPECTION WAS DONE AND THAT ALL I HAD TO DO WAS REINSTALL THE BORESCOPE PLUGS AND CLOSE UP THE ENG. I DID THIS AS IT WAS GETTING CLOSE TO DEP TIME. I WAS UNAWARE THAT THE GEAR BOX PAD HAD NOT BEEN REINSTALLED; AS I HAD NOT REMOVED IT. I BELIEVE THAT THIS INCIDENT COULD HAVE BEEN AVOIDED BY HAVING HAD 2 MEN ASSIGNED TO THE ACFT; SO THAT ONE COULD HAVE STAYED WITH THE ENG FROM START TO FINISH OR BETTER PAPERWORK; LISTING WHAT HAD BEEN REMOVED AND NEEDED TO BE REINSTALLED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THE ACFT WAS A B737-300 WITH CFM 56-3C ENGS. HE SAID HE REPLACED THE BORESCOPE PLUGS BUT DOES NOT REMEMBER REPLACING THE DRIVE PAD COVER. THE DRIVE PAD COVER WAS NOT REPLACED RESULTING IN LOSS OF ENG OIL ON TKOF AND INFLT ENG SHUTDOWN AND EMER LNDG. BETTER PAPERWORK CTL FOR INDIVIDUAL SIGNOFFS HE SAID COULD HAVE PREVENTED THIS INCIDENT. HE ALSO STATED HE HAS NOT BEEN CONTACTED BY THE FAA.