the noise is actual squeeling of the bearings on the fan shaft. They loose lubrication and are running dry. If they run dry long enough, they begin to seize and can slow down the motor. No, the fan 'blades' cannot touch the sides of the blower housing. Many years ago, I heard of a fix where you could drill small holes at just the right place in the housing, you could put sufficient lubricant into the bearings to get you another year or so. If you replace the fan motor - make sure that you mark the fan blades with left and right. They appear identical, are unmarked, and they can be put on the wrong side. If you do that, the blower will barely work.