I installed my U310BT into my 2004 Silverado w/ Bose and Onstar so i had to use the GMOS-04 adapter. However after everything was installed it seemed that the only thing that did not work at all was the audio, i get no sound at all. Does anyone have any experience with the GMOS-04 adapter?

there is probably a problem with the GMOS, those Scosche modules are junk, i've seen so many problems with them, i would either try exchanging out the module with another one or possibly trying the Metra Axxess version, they tend to be a lot more reliable

It was the GMOS-04 adapter, i returned it back to crutchfield and had them send me back a replacement, now it's working flawlessly.

cool beans, sounds about right, glad it wasn't something crazy to fix.