What was found
AFTER GEAR RETRACTION ALL LIGHTS ON GEAR HANDLE & ANNUNCIATOR WENT DARK (NORMAL) , THEN LT MAIN GEAR UNSAFE (RED) AND GEAR DISAGREEMENT (HANDLE) ILLUMINATED FOR 3 SEC THEN ALL INDICATIONS BACK TO NORMAL. ALTERNATE GEAR EXTENSION PERFORMED. LANDING UNEVENTFUL. CFR CALLED AS PRECAUTION. TOWED TO GATE. FERRIED FOR REPAIRS. REPLACED THE NLG DOOR (FWD) LINKAGE IAW AMM TASK 32-31-61-000-801 AND 32-31-61-400-801. OPS TEST OF THE PRIMARY EXT & RET SYS GOOD. NO DEFECTS NOTED, ALL LIGHTS NORMAL. RETURNED TO SERVICE.