What was found
PILOT REPORTED THAT AFTER TAKEOFF LT MAIN WHEEL WOULD NOT RETRACT WHEN GEAR HANDLE SELECTED TO GEAR UP POSITION. BOTH A & B DISAGREEMENT LIGHTS REMAINED ILLUMINATED WHILE BOTH GREEN LIGHTS EXTINGUISHED. GEAR WAS RE-CYCLED IN AIR IAW EAP-78 & RETRACTED PROPERLY AT THAT TIME. THE CREW DECIDED TO RTF DEN & DECLARED AN EMERGENCY. DURING DECENT THE NOSE GEAR SHOWED A DISAGREEMENT WHEN GEAR HANDLE SELECTED DOWN. RED A & GREEN B LIGHTS WERE ILLUMINATED. DESCENDING BELOW 1500 TRIPLE CHIME & AURAL WARNING, GEAR, WERE RECEIVED. PROCEEDED WITH CHECKLIST EAP-78 UNSUCCESSFULLY. PERFORMED EAP-76 GEAR EXTENSION BY ELEC OVERRIDE, ALSO UNSUCCESSFUL. FINALLY CONTINUED IAW GEAR EXTENSION BY FREEFALL, AFTER COMPLETION OF CHECKLIST ALL RED LIGHTS EXTINGUISHED & ALL GREEN LIGHTS REMAINED ON. MX TROUBLESHOT TO NLG A DOWN LOCK PROXIMITY SENSOR. REPLACED PROXIMITY SENSOR PN 120-41125-001 IAW MM 32-61-01, OPERATIONS CHECKED GOOD PERFORMED OPERATIONAL CHECK OF LG EXTENSION & RETRACTION THROUGH NUMEROUS OF LG EXTENSION & RETRACTION, NO FAULTS NOTED. COULD NOT DUPLICATE, MLG DISCREPANCY, AT THIS TIME IAW MM 32-00-00.