Ya know why it does that no sound through the rear speakers. Becuz the rear speakers run off line leval. Meaning no power goes to them like rca wires for a amp Doh. I sugest when you change your head unit you rewire the rear speakers streight from the deck. If you look on the speakers in the rear the amp is attached to the left speaker. They are actuly woofers if you wana call them that. So rewire your rear speakers before you burn your car.