MD80 DEPARTING ON WORTH SID FROM DFW FAILS TO TURN TO 185 DEGS AS CHARTED.

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AFTER DEPARTURE FORT WORTH CTR REQUESTED THAT I CALL DFW TRACON ON LNDG REGARDING A POSSIBLE PLT DEV. THE FO AND I WERE PUZZLED BY THIS REQUEST; AS WE BOTH BELIEVED THAT THE DEP HAD BEEN NORMAL AND PROPERLY FLOWN. AFTER THINKING ABOUT IT FOR A BIT; I THOUGHT THAT POSSIBLY DEP HAD EXPECTED US TO BE ON ONE OF THE RNAV DEPS; WHEN WE WERE ON THE WORTH 5; DUE TO AN INOP FMS. I CALLED BACK TO DEP ON THE RADIO; AND ASKED IF THAT WERE THE PROB. HE REPLIED THAT WE SHOULD HAVE BEEN ON A 185 DEG HEADING; AND POSSIBLY HAD A WIND DRIFT PROB. THE FO AND I DISCUSSED THIS. WE BELIEVE WE HAD BEEN ON THE CORRECT HEADING. WE DID THINK THAT POSSIBLY A MOMENTARY HEADING DEVIATION CAUSED BY A WAKE TURB ENCOUNTER WE HAD EXPERIENCED HAD BEEN THE PROB. ON ARR; I CALLED THE TRACON. THE GENTLEMAN ON THE PHONE INFORMED ME THAT OUR TRACK HAD NOT AGREED WITH WHAT THEY HAD ANTICIPATED; OR OBSERVED FROM OTHER DEPARTING ACFT; THAT THEY WERE GOING TO FILE A PLT DEVIATION; AND THAT THERE HAD BEEN NO LOSS OF SEPARATION. THIS WAS A VMC DEP; AND AS SUCH A SUBSTANTIAL PORTION OF OUR ATTENTION WAS OUTSIDE. OF PARTICULAR CONCERN WAS THE B757 AHEAD OF US; AS WE APPEARED TO HAVE LESS SEPARATION FROM HIM THAN NORMAL. THERE WAS THE WAKE TURB ENCOUNTER; WHICH THOUGH NOT SEVERE; DID DEMAND SOME ATTENTION. PARTICULARLY FROM THE FO WHO WAS FLYING. I WAS ALSO TRYING TO LOCATE VISUALLY AN ACFT DEPARTING THE EAST SIDE AND OBSERVED ROUGHLY ABEAM US ON TCAS. AFTER SOME MORE DISCUSSION; AND CONSIDERING THE TRACON MANAGER'S INFORMATION REGARDING OUR TRACK VERSUS THAT OF THE OTHER DEPARTING ACFT; WE THINK IT IS POSSIBLE THAT WE FAILED TO CHANGE THE HEADING TO THE REQUIRED 185 DEGS WHEN WE SELECTED HEADING SELECT; AND THEN FAILED TO NOTICE AND/OR CORRECT THAT ERROR. THE SOLUTION APPEARS TO BE MORE FREQUENT; AND BETTER CROSS-CHECK; NOT ONLY ON THE FLT DECK AND THE SALMON BUGS; BUT THE RAW DATA.