I own a 1984 Case 210 Tractor that runs great and is in great condition. I am having a problem keeping the drive belt on. It stays on until I shift gears. Sometimes it stays on, but more often comes off when I shift. There does seem to be a little slack in the belt. I have lubricated where the bar from the idler pulley attaches, but have not tried anything else. I am not a mechanic by any means, and any help would be greatly appreciated.