SLIDE RAFT AT DOOR 4L OF B747-400 COMES LOOSE SHORTLY AFTER TKOF AND WEDGES AGAINST CABIN ATTENDANT SEAT. WHEN IT IS DETERMINED TO BE UNSERVICEABLE; THE ACFT IS DIVERTED FOR MAINT.

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IMMEDIATELY AFTER TKOF FROM RWY 32L AT ORD; WE RECEIVED AN INTERPHONE CALL FROM CHIEF PURSER. WE WERE INFORMED THAT THE SLIDE/RAFT AT DOOR 4R HAD PARTIALLY DETACHED AND WAS WEDGED; ALONG WITH THE SLIDE COVER; AGAINST THE FLT ATTENDANT JUMPSEAT. THE JUMPSEAT WAS IN THE EXTENDED POS. A CALL WAS PLACED TO DISPATCH AND CONFERENCE CALL WAS ESTABLISHED WITH MAINT CTL. FO MR X WAS SENT TO DOOR 4R TO FURTHER ACCESS THE SIT. FO MR X CALLED THE COCKPIT VIA INTERPHONE AND HIS OBSERVATIONS WERE RELAYED TO DISPATCH AND MAINT CTL BY FO MR Y. WHEN I ASKED MAINT CTL IF THE SLIDE/RAFT COULD BE DETACHED AND SAFELY MOVED TO AN AREA AWAY FROM THE PAX AND CREW; I WAS TOLD THAT DETACHING THE SLIDE/RAFT WAS NOT 'ADVISABLE' AND THAT DISARMING THE SLIDE/RAFT COULD BE A 'DELICATE' OP. IF IMPROPERLY HANDLED; A DEPLOYMENT OF THE SLIDE/RAFT WITHIN THE CABIN WAS A POSSIBILITY. MAINT CTL ADVISED THAT THE BEST COURSE OF ACTION WAS TO RESTRAIN THE SLIDE/RAFT IN ITS PRESENT POS AND PROCEED TO A MAINT STATION WHERE REPAIRS COULD BE MADE. FO MR Y WAS SENT TO ASSIST FO MR X IN RESTRAINING THE SLIDE/RAFT USING SEAT BELT EXTENSIONS AND PLASTIC TIES FROM THE SECURITY KIT. I ALSO HAD FO MR Y TAKE PICTURES WITH MY CELL PHONE CAMERA SO THAT FO MR Z AND I COULD HAVE A VISUAL PICTURE OF THE SIT. AT XA00 UTC; IN THE VICINITY OF VOR ZZZ WE BEGAN A DIVERSION TO ZZZ. IN THE INTEREST OF SAFETY; IT WAS DETERMINED THAT FUEL SHOULD BE DUMPED IN ORDER TO LAND AT A WT NO GREATER THAN THE MAX STRUCTURAL LNDG WT (630000 LBS) WHICH WAS THE MOST RESTRICTIVE WT LIMITATION. APPROX 112000 LBS OF FUEL WAS DUMPED COMMENCING AT XC02Z AND TERMINATING AT XC49Z. AN UNEVENTFUL LNDG WAS MADE AT ZZZ.