Regarding to noise issue after replaced new screw element on GA18+ API317363 noise was happen during unload condition . as per investigate and enquire that the new screw element installation by customer which perform to wrong procedure during installation gears into motor/screw shaft ,It might be take clearance problem of male/female rotor the screw element were change the position , and also inner gears and shaft was worn out from friction during mounting . when running in unload condition eventually the noise will be generate ,So in this case must be replace perform as recommend below