I just took the 2013 C6 for a test drive yesterday at Don Wheaton Chev, checking it out for "ncnmra" who is still interested in buying it. It had a terrible squeal from the engine compartment immediately upon start-up and it remained for the entire test drive. They suggested it was an over-tightened belt and agreed it would have to be corrected. There weren't many others issues so it proved to be a good vehicle.
I also noticed "creaking" from the transparent roof panel when going over bumps or sometimes hard cornering. I've had a vehicle with removable t-tops before that would periodically do that but on this C6 it was often enough to be annoying. I took the roof off before the test drive and all the outer "rubber" was intact and in good shape. Will lubrication solve that noise or is this common for the transparent roofs?