A B733 CREW DEPARTING PHX COULD NOT RETRACT THE GEAR ON INITIAL GEAR RETRACTION.

Narrative

ON DEP FROM PHX-PUR; THE GEAR HANDLE WOULD NOT RAISE ABOVE 'OFF' POS DURING POST TKOF RETRACTION. SO AFTER REACHING A SAFE ALT; WE ACCOMPLISHED THE APPROPRIATE CHKLIST; AND THE GEAR CAME UP; AND NO LIGHTS. WITH ALL CHKLISTS ACCOMPLISHED I INSTRUCTED FO TO INFORM MAINT CTL. AFTER CONFERRING WITH THEM; IT WAS DECIDED TO RETURN TO SKY HARBOR. SO WE BEGAN TO BURN FUEL TO A SAFE LNDG WT; BUT WITH MAINT CONCURRENCE; WE DECIDED TO SEE IF WE COULD GET THE LNDG GEAR TO OPERATE PROPERLY BY CYCLING IT A FEW TIMES; WHICH PROVED USELESS. ON OUR RETURN TO THE ARPT; WE WERE INFORMED THAT THE REMNANTS OF A TIRE HAD BEEN FOUND OFF THE END OF THE RWY. WE DECIDED MORE INFO WAS REQUIRED AND REQUESTED A FLY-BY. TWR INFORMED US THAT IT APPEARED THAT THE L FRONT TIRE WAS EITHER SHREDDED OR MISSING. WE BURNED FUEL DOWN TO A COMFORTABLE LEVEL AND INFORMED COMPANY; CREW; PAX OF SIT AND DECLARED AN EMER UPON OUR RETURN. THE LNDG WENT SMOOTHLY; AND WAS UNEVENTFUL. WE TAXIED CLR OF THE RWY; AND WENT DIRECTLY TO GATE. P.S. AFTER TIRES WERE INSPECTED; NO DAMAGE WAS FOUND!