Trouble connecting Ipod Touch 2G to Belkin Tunecast auto

Hi there! I just bought my Ipod Touch 2G on this Chritsmas and find it really cool, but... I have this one problem, when I try to connect it to my new Belkin Tunecast auto, it just doesn't stop sending the audio trough the internal speakers in order to ear the sound on the external ones, (in this case my auto-stero via AM/FM signal) and I know the problem is not the belkin transmiter because I also try it on my Ipod nano, and it works perfect there, so I think something happens with my Ipod touch, can you tell me if that's normal, I mean can the iPod Touch send the audio outside from the "charging port" like many others ipod's or it have to be done by the headphone output only, help me please, thanks!