CAPT FLYING MLG OVERSHOT ASSIGNED ALT. TFC SHOWN ON TCASII AS TA. CAPT WRESTLED THE ACFT BACK TO 6000 MSL. TFC PASSED APPROX 800 HIGHER AND 2 MI.

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ON DEP WE WERE ASSIGNED HDG 180 AND 6000. CONFLICTING TFC WAS CALLED OUT BY CLEVELAND DEP CTL 118.9 AT 7000 FT AT 2 O'CLOCK. LAYER OF BROKEN CLOUDS AT 6000 FT. WE WERE JUST BELOW LAYER AND OTHER TFC JUST ABOVE. OUR TCASII ALERT WENT OFF ABOUT 10 SECONDS BEFORE WE VISUALLY ACQUIRED TFC. (THERE WAS NO COMMAND TO ALTER COURSE; CLB OR DSND; ONLY 'TFC; TFC'.) I MADE THE STANDARD 1000 FT BELOW CALL AT 5000 FT AND WAS SIMULTANEOUSLY RUNNING THE AFTER TKOF CHKLIST. I CALLED ALT AND PUT MY HANDS ON THE YOKE AT ABOUT 6200-6300 FT. THE CAPT WAS ALREADY 'PUSHING OVER' TO DSND RAPIDLY. WE HIT 6400 FT (MAX) AND THEN DSNDED RAPIDLY. THE CONFLICTING ACFT CROSSED OVERHEAD AT 7000 FT AND WE WERE AT 6000-6100 FT. FACTORS CONTRIBUTING TO CONFLICT: CAPT WAS HAND FLYING THE ACFT (AUTOPLT WAS AVAILABLE BUT NOT IN USE BECAUSE THE AUTO THROTTLES WERE INOP). ALT ALERT WAS ARMED AND WENT OFF PER OPS SPEC AT 6250 FT. MY (FO'S) FLT MODE ANNUNCIATOR (FMA) ALT WINDOW WAS PLACARDED INOP. THE ACFT WAS EXTREMELY LIGHT (108000 POUNDS; 54 PAX; 54 MIN FLT; LIGHT FUEL LOAD). OUR RATE OF CLB; BECAUSE OF THE WT; HAD BEEN IN EXCESS OF 3000 FPM. NORMALLY; WITH AUTO THROTTLES ON; THEY AUTOMATICALLY CUT BACK JUST PRIOR TO ALT LEVEL OFF. MANUAL THROTTLES DON'T. WE WERE DISTRACTED; IE; BUSY LOOKING FOR THE CONFLICTING TFC (BECAUSE TCASII HAD JUST GONE OFF) RIGHT ABOUT LEVEL OFF ALT OF 6000 FT. THAT; COMBINED WITH A HIGH RATE OF CLB; NO AUTO THROTTLE CUTBACK; NO FO FMA ALT WINDOW READOUT; AND A CHKLIST IN PROGRESS; CONTRIBUTED TO THE ALT OVERSHOOT.