What was found
UPON TURNING ONTO RUNWAY TAXIWAY 90 DEGREES TO RWY, FELT A STRONG BUMP THAT FELT LIKE IT WAS THE NOSEWHEEL. TURNING ONTO RUNWAY, NOSEWHEEL SKIDDED LIGHTLY AT LOW SPEED, ON TAKEOFF ROLL APPROACHING 100KTS, LOST STEERING. TROUBLESHOOTING AND BITE TEST OF BSCU'S, CLASS III FAULT "WORN SERVO VALVE-NWS, 5112CC. "PERFORMED FUNCTIONAL CHECK OF NWS IAW AMM 32-51-00-720-801. NO FAULTS; TSM 32-50-00-810-830 A PAR 3A, 1, CHANGED SERVO VALVE-NWS. REF AMM 32-51-51. REF ODI LOG 2204724.327360. R & R NWS SERVO CONTROL IAW AMM 32-51-51. ACCOMPLISHED LEAK AND OPS CHECKS IAW AMM 32-51-51. NO FAULTS OR LEAKS NOTED.