If it's your blower shaft bearings and you haven't been greasing them then they are likely shot, possibly along with the blower shaft.
Either that or your blower motor needs to be replaced, a dying motor here can also cause some noise.
For now, when greasing those bearings- do it while running, add the grease slowly and do it until clean grease is flinging out of the bearings. And definitely start doing it according to the PM schedule.