MLG HAS CTL PROB OK TKOF; MISSES ALT ASSIGNED.

Narrative

IT HAD BEEN MY TKOF FROM STL EARLIER BUT IT WAS WINDY IN STL AND ON LIFTOFF THE ACFT ROCKED SOMEWHAT. WE DID NOT THINK ANYTHING OF IT. IN CVG THE CAPT PERFORMED THE TKOF. UPON ROTATION THE ACFT AGAIN ROCKED L TO R THEN BACK. IT ACTED AS THOUGH THERE MAY HAVE BEEN ICE ON THE WING BUT THAT WASN'T THE CASE. IT WAS 90 DEGS F IN CVG AND THIS WAS A DC9-10 WITH NO ODD ICING CHARACTERISTICS AS THE MD80. THIS ROCKING CONCERNED US GREATLY SINCE IT WAS MORE PRONOUNCED ON THE SECOND TKOF. WE WERE CLBING TO FL250. AT FL240 I CALLED 1000 TO GO 24 VOR 25 AND THE CAPT ACKNOWLEDGED THE CALL. HE CONTINUED TO DISCUSS THE POSSIBILITIES THAT HAD TO BE CONSIDERED DUE TO THE WAY THE ACFT ACTED ON TKOF. IT WAS PRESENTLY ON AUTOPLT. AS I PUT AWAY MY CVG CHARTS I HEARD THE ALT BELL WE WERE AT 25250 FT AND CLBING. I CALLED ALT AND THE CAPT DSNDED BACK TO FL250. I BELIEVED THE HIGHEST WE GOT WAS FL254. ON THE WAY BACK CTR REQUESTED OUR ALT. I READ WHAT IT WAS AT THE TIME FL252. I ASKED CTR IF THERE WOULD BE A PROB WITH THIS AND THEY SAID 'NO.' ON ARR IN STL THE LNDG WAS UNEVENTFUL. WE CARRIED AN ADDITIONAL 20 KTS ON FINAL. MAINT DETERMINED THAT IT WAS AN AUTOPLT YAW DAMPER PROB. I GUESS THE WAY TO PREVENT SITS SUCH AS THIS WOULD BE TO DO ONE THING AT A TIME; BUT THAT GETS RATHER DIFFICULT IN A 2-MAN OP ON SHORT FLT LEGS AND THEN ADD IN A PROB THAT REQUIRES THOUGHT AND PREPARATION.