box should only be adjusted with steering box central, it should have no play at the center with play increasing towards both locks, if you remove play either side of center it could then be too tight going through the center, its adjusted by slackening the nut then winding adjuster screw in (clock wise) to remove play other to increase it , it helps to rock input shaft uj by hand as you adjust so you can feel play and when play is just removed,because of center tight spot steering box been set central when driving in a straight line is important, but if its only one direction thats effected its more likely something else like input shaft