I have found where I can adjust the volume of the voice guidance but I can only get the nav unit to lower the volume of the stereo a little bit when it is doing the voice guidance, I can not get it to mute the stereo. Is there an option to mute the stereo while the nav unit is speaking?

Since it mutes when you talk to I would think the other way would be possible.

 

I've been working on this one, too. No luck so far.

Cheers.