Car radio volume problem

[vvelez5]

I need some help guys. I tried using my Thrive through my Car Radio and since it doesn't have a 3.5mm auxiliary jack, I'm plugging it in the back with a RCA to 3.5mm cable. Problem is the volume is very low through the speakers. The music is playing and I can hear it but it's ridiculously low. Also the only way I can control the volume is through my thrive which isn't helping. I thought it was something wrong with my stereo but it looks like that its my Thrive that just won't allow the volume to be raised higher.