FO OF AN ACR WDB OVERSHOT ASSIGNED ALT DURING VECTOR CLB FOR TFC SEPARATION.

Narrative

AFTER TKOF FROM IND WE WERE CLBING TO AN ASSIGNED ALT OF 15000 FT. THE FO WAS THE PF AND WAS USING THE AUTOPLT; THE CAPT WAS OPERATING THE RADIOS AND NAV FUNCTIONS. CLBING THROUGH APPROX 13000 FT; CTR (EITHER ZID OR ZAU; I'M NOT SURE WHICH) ASKED IF WE HAD 'JETSTREAM' TFC AT 10-11 O'CLOCK POS AT 16000 FT. I RESPONDED THAT 'WE WERE LOOKING.' CLBING THROUGH 14000 FT; I SAW AND CALLED THE TFC AT 10 O'CLOCK POS. THE TFC WAS MOVING AWAY AND APPEARED TO BE 4-5 MI AWAY. THERE WAS CLRLY NO CONFLICT. CTR THEN ASKED IF WE COULD ACCEPT A VECTOR FOR CLB AND I SAID YES. I WAS ANTICIPATING; AND APPARENTLY THE PF WAS TOO; THAT CTR WAS ABOUT TO CLR US TO CONTINUE CLBING WHILE MAINTAINING VISUAL SEPARATION. CLBING THROUGH APPROX 14000 FT; CTR GAVE US A TURN TO 260 DEG HDG AND NO CLB. THE FO STARTED A LEVELOFF WITH THE VERT SPD WHEEL OF THE AUTOPLT BUT DRIFTED ABOVE 15000 FT BY 300 FT. I CAUGHT THAT WE WERE GOING THROUGH 15000 FT AND SAID '15000 FT IS THE ALT -- YOU'RE GOING HIGH.' HE WAS ALREADY CORRECTING WHEN THE CTLR SAID 'WHAT'S YOUR ALT? I DIDN'T CLR YOU TO CLB; ONLY TO TURN.' I RESPONDED THAT WE WERE LEVEL AT 15000 FT BECAUSE BY THEN WE WERE. THE CTLR THEN GAVE US A CORRECTED LCL ALTIMETER SETTING AND NOTHING MORE WAS SAID. THE 16000 FT JETSTREAM TFC WAS VIRTUALLY OUT OF SIGHT AND WAS NO FACTOR. I DON'T KNOW IF ANY AUTO ALARM PARAMETERS IN THE CTR WERE ACTIVATED OR NOT BUT THERE WAS NO HAZARD TO ANYONE. I RESOLVED TO BE EVEN MORE ATTENTIVE TO LEVELOFFS WHEN I'M NOT AT THE CTLS AND TO NOT ANTICIPATE WHAT THE CTLR IS GOING TO SAY. I FEEL THAT THE QUESTION ABOUT OUR CHOICE TO VECTOR FOR CLB AND THE UNEXPECTED TURN JUST A FEW HUNDRED FT PRIOR TO LEVELOFF WAS AN UNNECESSARY DISTR WHEN THE TFC IN QUESTION WAS CLR. SURELY THIS 'CONFLICT' COULD HAVE BEEN RECOGNIZED EARLIER BY CTR OR FOR THAT MATTER IGNORED. EITHER WAY; WE WOULD NOT HAVE BEEN DISTR JUST SECONDS BEFORE LEVELOFF.