B757 CREW HAD TRACK DEV ON DEP AT FLL.

Narrative

ON DEP FROM FLL; TALKING TO MIA DEP CTL; RECEIVED INSTRUCTIONS TO TURN L TO 270 DEG HDG AND 'JOIN THE THNDR.' OUR FLT PAPERS GAVE US A ROUTING OF FLL DIRECT THNDR; THE PDC GAVE THE FLL 8 DEP THNDR TRANSITION. THE CAPT ANNOUNCED ON BRIEFING THAT FLL 8 SAID CLB RWY HDG TO 500 FT. I GLANCED AT THE DEP PAGE AND CONCURRED; ASSUMING WE'D GET RADAR VECTORS TO THNDR. WHEN CTLR KEPT REPEATING 'JOIN THE THNDR' I THOUGHT IT ODD; BUT UNFORTUNATELY DIDN'T QUESTION IT OR I WOULD HAVE DISCOVERED WE WERE SUPPOSED TO FLY A TRANSITION SOONER. I ALSO ASSUMED THE LINE ON THE MAP WAS THE CORRECT TRANSITION -- BUT IT WAS THE ORIGINAL RTE; FLL DIRECT THNDR; AND NOT THE DHP 335 DEG RADIAL TO THNDR THE SID SHOWS. THEREFORE; WE WENT E THROUGH THE 335 DEG RADIAL WHEN CTLR HAD US TURN BACK TO 270 DEGS TO JOIN PROPER DEP. I SHOULD HAVE CHKED SID MORE CLOSELY AND HAD IT SET UP. I SHOULD HAVE QUESTIONED 'JOIN THE THNDR.' ALSO; FLL 8 NOT IN FMC; WHICH HELPED ME IN MY 'ASSUMPTION' (ANOTHER THING I SHOULD NOT HAVE ASSUMED WAS THAT IT WAS A RADAR VECTOR DEP).