What was found
AFTER T/O FLAPS WOULD NOT RETRACT. OVERHEAD PANEL INDICATED FLAP SYS 2 FAULT & WHEN HANDLE RAISED THE FLAPS STAYED AT 20 DEG AND FLAP SYS 1 FAULT CAME ON. THERE WAS NOT A FLAPS LIGHT ON SPFI PANEL AT ANY TIME. RECYCLED FLAP HANDLE IAW QRH & GOT SAME RESULTS & INDICATIONS EACH TIME NORMAL LANDING ACCOMPLISHED WITH FLAPS IN 15/20 SETTING. R&R NR 6 LT DOWNDRIVE FLAP TRACK GEARBOX IAW AMM 27-54-15-4. R & R LT FLAP NR 2 SCREWJACK IAW AMM LT FLAP NR 2 SCREWJACK IAW AMM 27-54-22. PPU 3CN AND PPU 27CV ON FLAP DRIVE UNIT REPLACED IAW MM 27-55-12-4 AND 27-51-19-4. NOTE THE NR 6 GEARBOX WAS CAUSE OF DISCREPANCY OTHER ITEMS CHANGED FOUND DURING TROUBLESHOOTING ITEM OR CAUSE BY TROUBLESHOOTING ITEM .