Fan to blow heat on floor makes terrible noise?

[02GreyTahoe]

Being as how it is winter, I have recently started to use my heat again. Whenever you have the climate control set to blow the heat out onto the floor, the fan or something makes a terrible screeching noise. Now the rear works fine and every other setting for where the air can blow out of the vents it doesn't make the sound. Anybody else have any experience with this or a solution without having to replace too much, like maybe a bent fan blade or something?

 

[darkoverlord]

I've notice this in my Tahoe recently, hopefully someone here will have an answer.