[SoCal LS-L]

Wow the thumping from the rear, if it only happens while turning sounds like your rear differential is faulty. Have you checked the fluid? Its pretty easy. And as far as your speaker problem goes.... it happens more when you hit the gas?? Is your system all stock or do you have any aftermarket components? When your speakers cut out like that, one of the most common problems is a shorted speaker wire..... could be hitting ground or hitting the other wire..... that will short the power stage and kill the sound momentarily. Check the wiring at each speaker.... starting with the rear since they are the easiest. Make sure the leads are not touching metal and the wires arent shorting together.