I am new to this site and wish everything that I have bought had a supourt group this good.This site is great

I just purchased a new D3 with the XM nav. I’m trying to get everything figured out before I start to do the install. I have a 07 Chevy Silverado the new body style not the classic.

My questions are when I hook up the VSS wire do I need to do it from the wire under the hood and use the adaptor that I saw from the other web site that was recommended from this site or can I hook it up to what ever the signal wire that the stock radio has for the auto volume, if so do I still need to have the adaptor?

Next question is what happens if you don’t have the VSS wire hooked up? Will the Nav not be as accurate as it could be? And if so within a couple of feet or like miles?