Hi longcut, i have a 2412, and it doesn't make any noise like you describe. It sounds like the servos are "hunting". this usually happens when the gain is not set properly in the control. basically, when sitting still, the servo jumps back and forth between marks on the encoder. Hunting is nothing major, its actually normal, but you will need a maintenance man, or someone who can tune them on a Fanuc control to where you cannot hear them hunting. If they get REALLY out of tune, the hunting will get so violent the table/spindle will jerk back and forth.
Also, you may want to adjust your gib strips per the instructions in the manual, if they have wore and loosened up slightly, this may be allowing the table to move a tenth or two, and creating the hunt in your servos, just an idea, i am not maintenance pro. I adjusted my gibs last weekend, took about 2 hours, but was not hard to do.