How does the back seat fold down on a 2008 Chevy impala?

You cannot easily move the seat. There are gears on both tracks that are turned by cables. May need to replace the complete seat frame, I don't think the parts are serviced separately.

If you have the long bench I don't think you can fold the rear seat down. It will only fold down if you have the split rear bench.

The back seat of the Impala can only be folded down if your vehicle is the particular fold-down version, otherwise, it'll have to be removed entirely to gain access to the massive available space.
To remove the seat, follow these steps:
• Push down on the bottom cushion of the back seat.
• Pull-on the T handles which are under the front edge of the seat, to release the bottom cushion
• Remove the cushion
• Unwind the nuts and bolts on the bottom part of the back seat. Then lift it, and it would be released from its position.
• Now, remove the seat from the back and you can access the trunk.

First make sure you even have the rear seat fold down option. Many, if not all, LS Impalas don't have the option. Easiest way to check is to open the trunk and look for the latching hardware at the back of the back seats.

To fold-down rear seat on 2007 Chevy Malibu, follow these steps:
1. Open the trunk
2. Pull on one or both the handles located on the upper side of the trunk
3. The handle located on the driver's side will unlatch the bigger part of the read seat
4. The handle on the passenger side will fold down the smaller portion of the rear seat.
5. Once done, you will have a seat that's nicely folded down.

https://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Ownership/Manuals_and_Videos/02_pdf/2011_Impala_Owner_Manual.pdf Look on 3-8 for instructions on how to fold down the rear seat only if your car is equipped with fold down seats. Not all Impalas have this feature.

To fold down, follow these steps:
1. There is a loop located in the middle of the back seat - pull it forward and the bottom part of the rear seat will fold down
2. Wedge the the back seat, and it should not give you any trouble in folding down
3. To ensure that the seat goes all the way down- remove the headrest.
If your seat can not be folded-down, follow these steps to remove it:
1. Put some pressure on the bottom cushion of the back seat.
2. To release the bottom seat, pull the T handles, and then remove the cushion
3. There will be some bolts and screws on the bottom of the seat - remove them, and then you can pull out the seat.

If back seats fold down like my 2003 Impala, you should be able to access trunk through back seat. There is an emergency release in the trunk to open trunk lid

The rear seat backs do not fold down in these trucks, the seat bottom lifts up to gain access to the compartments below but the seat back does not fold down. The only thing you can do is physically remove the rear seats.

in the middle of the seat cushions in the back of the seat there is a little loop, pull that loop forward and that will have the seat's bottom pulled down to the floor agains the back of the front seats. Next simply apply a lil muscle to the back of the back seats and the seats should fold down nicely into the open space. Be sure to remove the headrests so the seat will fold all the way down. post any issues u may have.