2006 FX4 Ext cab... there's a big black case bolted to the bottom of the rear seat on the drivers side. Must be 3 feet in length, a foot wide and about inches deep. It looks factory, like it could hold the jack and hardware, but I see no way to open it. Just got the truck last week, I'm waiting for the owners manual from the dealer... any idea what this is??? if needed I can post a pic.
Thanks!

 

You sure it's not the factory sub woofer?

 

May be.... The Stereo does really sound great...

 

It is your sub., congrats.

 

I have the same system, I sounds great!! Congrats on the find.
" 500watts plus 8" sub" under that seat.

 

Took me 2 days to find the Sirrius was still hooked up also!
That's really great... thanks everyone

PS - let me know if you find a company that makes a replacement shifter
(console model)