I have a 72 inch cut mower deck attached to my 855 tractor. I've notice that I have a idler sheave on the deck that I can rock up & down by hand in a vertical motion. So far it's not having any affect or wear on the mower belt & I can't detect any noise either. Im concerned about it because the mower deck belt is like well over $100 bucks to replace. But now I am not sure if having vertical play in an idler pulley bearing is a sign that I have a bad bearing that should be replaced. All the parts on this deck except for the three mower blades, are all original equipment. It's been in service since 1989 & is used to cut five acres from late April to mid November.