FYI: I have upgraded the ground wire from the frame to the battery from the original 8AWG to 2 AWG OFC as part of an audio build (of course, then I decided just to ground straight to the battery, haha). After this, reduced if not eliminated headlight dimming and my transmission seems to shift with less clunkification, although that could just be my brain making that part up, but I'll take it. My 2011 Silverado's headlights dimmed when I first turned on the signals... no other car I have ever had did this. My 2014, same thing. Baffles me that this was not engineered out - stupid and embarrassing.
Later I I also added a 2AWG wire from the engine block to the battery and added another OEM grounding strap to the OEM location. This did nothing but cost me time.
I believe the lights at least if not the steering and tranny ground to the frame so their ground would be going through the 2AWG to get to the battery (in theory).