ACFT PERFORMANCE PROB AT HIGH ALT.

Narrative

AFTER TKOF; THE STATUS MESSAGE 'MAIN GEAR WARNING' APPEARED ON THE LOWER EICAS. SINCE THERE WAS NO UPPER EICAS MESSAGE IT WAS ASSUMED AT THAT TIME TO BE AN ELECTRICAL INDICATION GLITCH. DURING CRUISE; A CLB FROM FL310 TO FL350 WAS REQUESTED WHEN THE FMC SHOWED AN OPTIMUM ALT OF FL332. ATC REQUESTED AN EXPEDITED CLB THROUGH FL330. THE SPD WAS REDUCED AND SET TO MACH .76. THE ACFT WAS ON AUTOPLT. AT FL347; THE ACFT APPEARED TO BE INITIATING A LEVELOFF AS NOTED BY A DECREASING ASCENT RATE. HOWEVER; SECONDS LATER THE ALT ALERT SOUNDED AND THE ACFT WAS DSNDING AWAY FROM ALT. THE INITIAL THOUGHT WAS THAT THE ACFT MAY BE UNABLE TO HOLD FL350 DUE TO A PERFORMANCE LIMITATION NOT INDICATED BY THE FMC. THE AUTOPLT WAS DISCONNECTED AND THE ACFT NOSE RAISED GENTLY TO ATTEMPT TO ATTAIN A LEVELOFF AT FL350. AT THAT TIME THERE WAS A MUTED STICK SHAKER. THE NOSE WAS IMMEDIATELY LOWERED AND THE SPD INCREASED. THE STICK SHAKER WAS VERY BRIEF AND THE ACFT WAS LEVELED OFF AT FL350. THERE WAS A QUESTION AT THE TIME AS TO WHETHER IT HAD BEEN A STICK SHAKER SINCE IT HAD BEEN SO MUTED. THE FLT CONTINUED NORMALLY; HOWEVER; ON DSCNT; AN UPPER EICAS MESSAGE 'GEAR DOORS' APPEARED AND THE 'GEAR DOOR' CHKLIST WAS COMPLETED. ALSO; DURING THE DSCNT; THE SPD BRAKES WERE USED. WHILE IN THE EXTENDED POS; THERE WAS MORE NOISE AND VIBRATION THAN IS USUAL. NO EXCESSIVE FUEL BURN WAS NOTED ON THE FLT. IT IS POSSIBLE THAT THE LOAD MANIFEST DID NOT REFLECT THE CARGO WT CORRECTLY. IN HINDSIGHT; THE CARGO SHOULD HAVE BEEN REWEIGHED AFTER LNDG; BUT THIS WAS NOT DONE.