Look at the bearings for pitting, scuffing or discoloring. Also look at the axle surface that rides against the bearing. Check it for scuffing, grooving. Before you pull the axle out see if the axle is loose, lift it up and down while holding it at the flange end. You can also look close at the seal and see if it cracked or split. Sometimes they get old and hard and it doesn't take much for them to go bad.
