Given how noisy these machines are, I don't know how you could hear a bearing noise when accelerating or cruising, unless it was very, very worn out.
Have you jacked up the rear yet and just spun the tire over by hand? If it is a bearing, you should be able to hear or feel a "coarseness". Best test would be to first check with the belt installed, then slacken and remove the drive belt to remove the bevel box from the mix for test 2.
