Hello;

Does this type of furnace have a belt or strap on the blower? Lately, its been making a very annoying rattling sound, I opened it up to have a look, and noticed a piece of leather inside the blower. I removed it, and the noise is gone! The blower works beautifully, and no more noise.

I would pull out the blower and wash out the blower wheel. It's probably very dirty and hurting your airflow greatly. There is no leather strap around the blower. You may need a new belt, but make sure to get one from an HVAC parts dealer as they have a different kind of belt from an auto parts seller.