I don't have an m240i (yet!) but I can say I know what you're describing when in 4 wheel drive. That's obviously different than AWD, but kind of similar. I notice differences between the two modes in my truck. In 4wd there is a definite difference in the vibrations that are felt underfoot. It's probably a combination of several things that cause it. Not sure if that helps, but no, you're not imagining things... at least I don't think
