MECHANIC REPORTS USING AN INCORRECT ACFT MAINT MANUAL REFERENCE TO REMOVE; REPLACE AND TEST A LEFT MAIN LNDG GEAR GROUND SENSE (SHIFT) PROX SENSOR ON A B727-200. PROCEDURE USED WAS FOR MLG DOWN LOCK PROX SWITCH.

Narrative

I USED AN INCORRECT ACFT MAINT MANUAL REF TO REMOVE REPLACE; AND TEST A L MAIN LNDG GEAR GND SENSE PROX SENSOR. THIS WAS DONE ON A B727-200 ACFT. I USED THE REMOVE AND REPLACE AND TEST PROC FOR THE MAIN LNDG GEAR DOWN LOCK PROX SWITCH. THE TEST PROC WAS DIFFERENT. I CHKED THE OP OF THE GND SENSE SYS AND THE PROX SENSOR THAT I CHANGED AND THE SYS TESTED 'GOOD.' THE ACFT HAS FLOWN MULTIPLE LEGS WITHOUT A REPEAT OF THE ORIGINAL PROB. THE SAFETY AND AIRWORTHINESS OF THIS ACFT WAS NOT AFFECTED. I KNOW THIS BECAUSE I VERIFIED THE OP OF THE GND SENSE PROX SENSOR. IT WAS OPERATING NORMALLY. I INCORRECTLY USED THE WRONG ACFT MAINT MANUAL REF DUE TO LACK OF SLEEP. I WILL; IN THE FUTURE; TAKE TIME TO RESEARCH THE COMPONENT I AM CHANGING; AND OPERATIONALLY TESTING TO ENSURE COMPLIANCE WITH THE PROPER ACFT MAINT MANUAL REF. THE ACFT FLEW 2 LEGS AND WAS SCHEDULED TO HAVE THE GND SENSE PROX SENSOR INSTALLATION AND FUNCTIONAL TEST TO BE COMPLETED IN ACCORDANCE WITH THE PROPER ACFT MAINT MANUAL REF PROC. THIS INSPECTION AND OPS CHK PROVED THAT THE SENSOR WAS INSTALLED CORRECTLY AND FUNCTIONALLY TESTED 'GOOD' IN ACCORDANCE WITH THE ACFT MAINT MANUAL FOR THAT COMPONENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: REPORTER STATED HE HAD CHANGED THE LEFT MAIN LNDG GEAR GROUND SHIFT (SENSOR) PROX SWITCH DUE TO THE B727-200 WAS STILL IN THE 'AIR' MODE INSTEAD OF THE 'GROUND' MODE. THE MAIN LNDG GEAR INNER PISTON STRUT WAS FOUND TO BE TOO HIGH ON THE GEAR STRUT AND NOT ALLOWING THE GROUND SHIFT MECHANISM TO POSITION FOR A 'GROUND' MODE. REPORTER STATED THE ACFT'S ENTIRE 'AIR-GROUND' SYSTEM WAS CHECKED AT THEIR MAINT BASE AND FOUND TO BE OPERATING CORRECTLY.