A GEAR UP LOCK PROB IS SENSED BY THE B757'S EICAS SYS BUT THE PIC BYPASSES THE CHKLIST PROC AND HAS THE FO LOWER AND THEN RAISE THE GEAR SHORTLY AFTER TKOF FROM SAT; TX.

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WE HAD JUST TAKEN OFF FROM SAT ON RWY 3. THE CAPT WAS THE PF. AFTER GEAR RETRACTION; THE CAPT AND I BOTH NOTICED THAT THE AMBER GEAR LIGHT REMAINED ILLUMINATED. THERE WERE NO OTHER ANNUNCIATOR LIGHTS ILLUMINATED. THIS WAS IMMEDIATELY FOLLOWED BY THE (GEAR DISAGREEMENT) EICAS MESSAGE. FIGURING THIS WAS A MICROSWITCH PROB ON ONE OF THE GEAR UPLOCKS; I PLANNED ON WAITING A MIN OR 2 TO SEE IF THE PROB WOULD TAKE CARE OF ITSELF. ABOUT 10 SECONDS AFTER THE EICAS MESSAGE DISPLAYED; THE CAPT COMMANDED 'GEAR DOWN'. I PLACED THE GEAR LEVER IN THE DOWN POS AND THE GEAR EXTENDED NORMALLY. IT WAS AT THIS POINT IT OCCURRED TO ME WE SHOULD HAVE REFED THE QRH INSTEAD OF PUTTING THE GEAR DOWN. THE CAPT THEN COMMANDED 'GEAR UP'. I PLACED THE GEAR HANDLE IN THE UP POS; AND THE GEAR RETRACTED NORMALLY WITHOUT ANY DISAGREEMENT LIGHT OR EICAS MESSAGES. AFTER THE PROB WAS TAKEN CARE OF; THE CAPT REFED THE 'GEAR DISAGREE' CHKLIST IN THE QRH. BASED ON OUR PARTICULAR SIT; WE SHOULD NOT HAVE CYCLED THE GEAR. WE PROCEEDED TO OUR DEST WITHOUT ANY FURTHER PROBS. WE NOTIFIED MAINT UPON LNDG AND THE CAPT WROTE UP THE MALFUNCTION IN THE LOG. IN THE SPIRIT OF 'TAKING CARE OF THE OBVIOUS;' I IGNORED AN EICAS CAUTION MESSAGE AND DID WHAT THE CAPT SAID VERSUS SITTING BACK FOR A MOMENT TO ANALYZE THE SIT. HAD I DONE THIS; IT WOULD HAVE OCCURRED TO ME TO REF THE QRH. I WOULD HAVE RECOMMENDED COMPLETING THE 'GEAR DISAGREEMENT' ABNORMAL PROC TO THE CAPT VERSUS SIMPLY COMPLYING WITH HIS COMMAND. SUPPLEMENTAL INFO FROM ACN 543349: A GEAR DISAGREEMENT CAUTION MESSAGE; CAUTION LIGHT AND GEAR AMBER LIGHT ILLUMINATED. ACCOMPLISHED THE GEAR DISAGREE AND GEAR DOORS ABNORMAL PROC. GEAR EXTENDED NORMALLY. WARNINGS AND CAUTION LIGHTS EXTINGUISHED; GEAR RETRACTED NORMALLY; LIGHT EXTINGUISHED; THEN PROCEEDED TO DEST. IN RETROSPECT; IMPROPER USE OF QRH AND/OR INCORRECT CHKLIST.