What was found
FELT AND HEARD A STRONG VIBRATION AFTER GEAR RETRACTION. HAD A LEFT GEAR RED LIGHT (A SYSTEM). CYCLED GEAR, VIBRATION STOPPED. HAD 3 GREEN LIGHTS WHEN GEAR CAME UP THE VIBRATION STARTED AGAIN AND CONTINUED UNTIL GEAR WAS DOWN AND LOCKED. RED GEAR LIGHT WAS ILLUMINATED UNTIL GEAR WAS DOWN AND LOCKED AND HAD 3 GREEN. REPLACED LEFT MAIN LANDING GEAR A SYSTEM UPLOCK PROXIMITY SENSOR IAW MM 32-61-01. LANDING GEAR INDICATION AND OPERATION CHECKS GOOD. ABLE TO DUPLICATE GEAR DOOR WOULD NOT CLOSE CAUSING VIBRATION. DOOR OPS GOOD WITH NEW PROXIMITYSENSOR.