At the moment, I have that seat folded down since no one sits there and there is no rattle. This car is sooo quiet that you hear every little peep. Smiles, Dan There are all sorts of loose connectors under the seat that could rattle, and the fasteners (metal clips) that hold the seat bottom down look like they will squeak and rattle if the seat is not secured properly, or one of the metal clips needs adjusting (bending). Pretty base design, but easy to work with. Just lift up on the front of the seat, and you will unclip the two clips. Make sure they align with the holes and reseat the rear seat, making sure it clicks into place. Good luck!