What was found
AFTER T/O FROM LGB THE GEAR WAS RAISED AND WAS CONFIRMED UP AND LOCKED UNTIL SLATS WERE RETRACTED AT WHICH TIME A THUMP AND SLIGHT SHUDDER WAS FELT AND L MAIN GEAR INDICATED UNSAFE. GEAR HANDLE WAS PLACED IN THE DOWN POSITION WITH ALL GEAR INDICATING DOWN AND LOCKED. UNABLE TO DUPLICATED, SUSPECTED BAD UPLOCK ACTUATOR. WHEN PERFORMING GEAR SWING PER M/M 32-31-00-516, PUT GEAR HANDLE IN NEUTRAL POSITION W/GEAR UP, AND HYD MULE PRESS WAS ABLE TO DUPLICATE PROBLEM ON ANOTHER A310 W/SAME PROBLEM. IT WAS T/S TO OPPOSITE SIDE MLG SEQ VALVE.