2 TECHNICIANS ASSIGNED TO WORK A BRAKE CHANGE ON A B767-300 RPT CONCERN ABOUT WORKING ON AN AIRPLANE WITHOUT ANY TRAINING ON THE AIRPLANE SYS.

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MYSELF AND ANOTHER MECH WERE GIVEN THE JOB OF FINISHING THE INSTALLATION OF THE #2 FRONT MAIN LNDG GEAR TIRE/WHEEL AND BRAKE AFTER THE BRAKE WAS REPLACED BECAUSE OF A HYD LEAK. WE TOOK OVER THE JOB IN THE MIDDLE OF THE BRAKE INSTALLATION. WE WERE GIVEN A TURN OVER FROM THE NIGHT SHIFT MECH. NEITHER OF US HAD EVER WORKED THE B767 BEFORE. WE OBTAINED THE MANUAL REFS FOR INSTALLATION OF THE BRAKE AND TIRE AND FOLLOWED EACH STEP. EVEN THOUGH WE WERE BOTH VERY FATIGUED WE FINISHED THE INSTALLATION OF THE #2 FRONT MAIN LNDG GEAR TIRE AND BRAKE ASSEMBLY UP TO INSTALLING THE RETAINER PLATES ON THE BRAKE QUICK DISCONNECT. THE BACKER PLATE OF THE RETAINER ASSEMBLY WAS FOUND TO BE CRACKED UPON REMOVAL. A NEW BACKER PLATE WAS FABRICATED BY OUR SHEET METAL SHOP BUT COULD NOT BE TREATED WITH THE PROPER PROCESS BECAUSE WE DON'T HAVE THE EQUIP TO DO THE TREATMENT PROCESS AT THIS STATION. AN ENGINEERING AUTH WAS PRODUCED FOR A TEMPORARY INSTALLATION OF THE BACKER PLATE UNTIL THE NEXT 'C' CHK; SO A NEW BACKER PLATE COULD BE OBTAINED. WE INSTALLED THE NEW BACKER WITH THE REST OF THE RETAINER; ACCOMPLISHED OPS CHKS AND LEAK CHKS PER THE MANUAL. NO LEAKS AND THE PLANE FLEW ITS NEXT MISSION ON TIME.