ALT OVERSHOT ON CLIMB WHEN FLT CREW DISTRACTED LOOKING FOR TRAFFIC.

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DEP CTLR CLRED US OUT OF 2000' TO CLB TO 6000 (FINAL EXPECTED ALT 8000'). BECAUSE OF HIGH OUTSIDE AIR TEMPS; I TOLD COPLT WE WOULD GO UP TO THE 8000' TODAY INSTEAD OF REQUESTING 6500' ON TOP VMC CONDITIONS. AT THAT POINT CTLR REQUESTED FLT TO EXPEDITE CLB THROUGH 6000'. COPLT WAS OFF THE FREQ IN ORDER TO GIVE TIMES TO OPS (PER OPS MANUALS/SPECS). COPLT CAME BACK ON FREQ AND CTLR AGAIN MADE REQUEST TO EXPEDITE THROUGH 6000'. BOTH XMISSIONS WERE REPEATED BACK TO CTLR. FIRST CAPT RESPONDED EXPEDITING THROUGH 6000'. SECOND REQUEST--COPLT RESPONDED WOULD EXPEDITE THROUGH 6000'. PLT MADE COMMENT TO COPLT SHE WAS CLBING AS FAST AS POSSIBLE (1300 FPM). AT 6600' CTLR SAID WE HAD BEEN CLRED ONLY TO 6000'. RADAR SHOWED US AT 6600'; AND HE THEN CLRED US TO CLB TO 8000'. WE CONTINUED OUR CLB TO 8000'. IN RETROSPECT THE CTLR PROBABLY SAID; 'EXPEDITE TO; NOT THROUGH 6000'.' WE HAD A MIND SET TO 8000' BECAUSE OF PREVIOUS DISCUSSION OF NOT GOING ON TOP AT 6500'; PLUS BOTH ACKNOWLEDGING TO EXPEDITE THROUGH 6000'. WE ALSO USED SECOND TRANSPONDER TO SET ASSIGNED ALTS IN. WHEN I CHKED ONLY 2000' (FIRST ASSIGNED ALT) AND 8000 (6/2) WERE SET IN. SUPPLEMENTAL INFO FROM ACN 93626: I HAD BEEN BUSY LOOKING OUT FOR OTHER ACFT. I WAS BUSY AND HAD NOT SET THE ALT IN OUR #2 TRANSPONDER. THIS OCCURRED ON THE THIRD DAY OF A 3 DAY TRIP AFTER 18 LEGS; HALF OF WHICH WERE OUT OF LAX.