I'm not sure that the 11-tooth idler gear is correct or not but you can get away with running an 11-tooth idler gear on both top and bottom positions. The upper pulley is a floating pulley, which means that the pulley is desigined to slide from left to right, relative to the direction of the bike, a few millimeters. They usually use a ceramic bushing for this on Deore XT pulleys. The lower pulley is riding on a sealed ballbearing and does not float.
Try taking them apart. The bushing needs some oil to keep it spinning freely and the lower pulley just needs to be cleaned on the outside. Do not try to take the bearing apart as there isn't anything you can do to it other than to mess it up.
Try taking them apart. The bushing needs some oil to keep it spinning freely and the lower pulley just needs to be cleaned on the outside. Do not try to take the bearing apart as there isn't anything you can do to it other than to mess it up.
