I have a '97 Chevy C1500 ext cab w/ 2 12" audiobahns (800 watts each) and I'm having problems with the panel behind the back seat vibrating. I was going to fill the space between that panel and the exterior panel with expandable foam, but someone told me it would rust bad. Is this a good idea? If not, please help me.

thanx

 

#1st try adding deading mat 1st
the foam is the last thing i will go to /why if i need to run wire i can not if someone hits you it will not fold there are more but you see what i'm getting at

 

If the deadening mat dont work try some foam that is used for making mattresses. it comes in different thickness and you can still run your wires then too

 

there should be no rust issue with the foam, if there is rust back there the foam should not accelerate nor stop it

If you use an aggressive foam you can easily bend sheet metal so dont get carried away if you go that direction. Check out the slow expanding foams that a boat shop would sell