What was found
SHIP 1804 - ATB JUST PRIOR TO COASTING OUT RECVD ALT DISAGREE EICAS F/O ALT + 250 ALSO NOTED UNUSUAL FLUCTUATIONS OF CAPT ALT PLUS/MINUS 80 FLUX INCREASED IN LIGHTEST TURBULENCE . CORRECTIVE ACTION: T/S PER B767-400 FIM 34-26-00-810-802. R/R ADM FOR LT SYST STATIC M11262 PER B767 MM 34-26. R/R LEFT ADIRU PER MM 34-26. VERIFIED ALT FLUC ON PUMP UP. VERIFIED P/S NOT AT FAULT NO LEAKAGE T/S PER B767 WDM 34-21. MEGGED ALL WIRES AT M11262. NO SHORTS TO ANY WIRE OR SHIELD AT 500V REPLACED LEFT AOA VANE PER MM34-26 ALL FLUCTUATIONS NOW ELIMINATED AIR DATA SYST NOW NORMAL. (9843820).