I dont have a rattle or a bang, but I do get a very high pitched squeal, almost like a whistle, when I got between 2.7 and 3G's +. I thought I'd keep it in this thread.
Sounds like something is about to snap, but I have wheeled like that always and been up to 5G's under highly stressful inclines in 4L, and never had anything break. Fluid levels are always fine. Seems to come from the front end. Any ideas?