If you have a magnetic base dial indicator, you can check the backlash. 0.008-0.012 is fairly typical. Set it up perpendicular to a tooth. Rock the bevel gear back and forth and read how much slop is there. Also, can grease (there is special compound for marking the pattern) and see if it is set too deep. Would likely be way down by the root of the tooth. It is possible some corrosion is on the teeth from sitting as well.