B737-700
Maintenance Airframe; Maintenance Powerplant
Situational Awareness; Time Pressure
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Human Factors; Incorrect / Not Installed / Unavailable Part
I was sent to aircraft to perform an [inspection] with another mechanic (Name) and found the #4 Main Landing Gear Tire worn beyond limits; along with a low O2 bottle. The plane had an outbound flight soon after we arrived so we had very little time to perform our check. We serviced the Crew O2 bottle and changed the tire and signed the logbook off in reference to the AMM task. I had no idea that the Washer (Item 15 in reference to AMM 32-XX-XX-XXX-XXX) was not installed with the axle nut. No abnormalities were present to show that the washer was missing; the safeties were installed like normal and hub cap installed.
B737-700 Maintenance Technician reported that after replacing the tire they realized a washer was not installed.