NexxTT

Forbid it be this, but if other clues fail to reveal problem, check for a bent left half-shaft.

economisTT

fortunately, my damage was considerably less than yours...only a cracked rear valence and a mess of deer guts everywhere they could be on the underside (the last of which were only eliminated when i replaced my eom exhaust with an mtm).

hope you get all of your problems fixed.

PatenTT

Instead of running the climate control on auto, hit econ and shut down the AC. It runs all of the time and some hissing cabn be the refrigerant flow through the expansion valve. (That's what mine does).

droptoptt

Our GM trucks at my work are notorious for "grabbing" & "oscillating" when any foreign matter collects on/in them.