Decibles

I want to swap to 3.73s but have a few questions first. What are some of the most quiet gears to get? What all do I need to purchase? What is a carrier?...3 series carrier...

And most important, does a swap like this void any warrantee? Could I bring my car to chevy and have them do the install?

Thanks a bunchy

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Red 2002 Z28 A4
Leather, T-Tops
All Stock.
Mods soon - Lid, Exhaust