Nav Install 08 Sierra W/ Bose

[Sir Dan]

Hey guys. Need a little sage advice here with a nav upgrade I'm planning. I've done tons of searching and reading here and all over the web, and there is a lot of confusion around whether or not you need the VSS/voice harness if you already have a bose system from the factory.

Has anybody here installed a factory nav unit in an already bose equipped truck that knows for sure if VSS is needed for Onstar and nav to work right?

[Majorleaguebass]

the onstar has nothing to do with the navi, but the navi needs the vss so if it loses signal, it can keep track of your speed so there is no delay in the navi.

[Sir Dan]

Okay, that makes sense I guess. And the "voice" part of it must be needed for the handsfree phone. I just can't understand why there are so many different opinions on whether you need the VSS/voice harness if you already have the bose option. Either the nav and phone work or they don't... right? I guess I can try it without and if it doesn't work correctly, I'll put in the VSS harness. Just thought maybe somebody on here had been down this road with the GMT900 trucks and had some firsthand knowledge.

Thanks