On my AVIC-D3, when I change the volume settings for the navigaton to Voice Navigation OFF it still speaks. It won't interrupt the music, just speaks over it unless i turn it ON.

 

Also, the volume level for the Navigation doesn't correspond to the Head Unit Volume, which is annoying going from city to highway where you need to turn the volume up.

 

Any ideas on these?

That's normal. You have to turn the voice volume all the way down to totally mute it. I hate the turn by turn voice, I muted mine .. But i see your point in the difference between city and highway volumes.

 

Just get accustomed to looking at the directions vrs. using the annoying turn by turn voice.