I am replacing the Mark Levinson stereo and retaining the original nav. Is there a way to retain the nav audio and run it through the new stereo unit? From what I understand, the Mark Levinson stereo processes the nav audio and creates the sound through the system.

 

Do you mean the entire ML system? (head unit, power amp, etc?0

If just the head unit, search on Beatsonics on this forum -- there's a (pricey) adapter unit when changing to an aftermarket head unit that retains most of the original functionality, including steering wheel controls.

 

Well I believe the Nav audio is only connected to the Driver Side Front speaker(s), not the entire cabin. This might indicate a direct output from the Nav to this speaker... just a thought. Another option in your situation is to add an input to the new headunit and dedicate it to the Nav system output by isolating the sound output on the Nav harness?

 

Here's the scoop on replacing the Mark Levinson radio in the SC430:

BeatsonicUSA has a kit to change out the radio and maintain the navigation system.
http://www.beatsonicusa.com/ (main site)
http://www.beatsonicusa.com/beat-sonic-mva-12l.html (The parts for conversion)

1. The NAV works through the AMP, not the radio, that’s how the nav system is retained (with the voice) and the screen for the NAV is able to be used for the DVD player with very decent quality.
2. The steering wheel controls are maintained, however, their functionality changes a bit.