What was found
WXR FAIL ILLUMINATED IN FLIGHT. GROUNDED - YES. INITIAL EVAL, NO SOUNDS HEARD FROM R/T OR NOSE. FLIGHT CREW REPORTED LOUD GRINDING NOISE BEFORE WXR FAIL APPEARED ON ND. PULLED AND RESET WXR R/T CB, LOUD GRINDING NOISE RETURNED. RMVD & RPLCD WXR ANTENNA DRIVE UNIT IAW B737-800 AMM 34-43-11-000/400-802. RESET CB. NOISE IS GONE. FAILS INSTALL TEST IAW AMM 34-43-00-710-802-001. CYCLED A/C POWER, NO HELP. PWS FAIL AND WXR FAIL ON ND. ND SHOWS ALTERNATING 0M/-9M ON RANGE. ALSO, ALTERNATES STAB/ATT/STAB/ATT. WXR RANGE DISAGREE ON BOTH ND, EVEN THOUGH BOTH EFIS CONTROL PANEL RANGE SET TO MATCH. RMVD & RPLCD WXR ANT DRIVE UNIT PER AMM 34-43-11-000-801/802 AND AMM 34-43-11-400-801/802 - OPS NRML. WXR SYST OPS TEST NORMAL PER AMM 34-43-00-710-802-001. ETOPS SIGNIF SYS - GND VERIFICATION SUCCESSFUL.