Does your Challenger have a rear axle gear whine at highway speeds? If so, last year, Chrysler put out a TSB (#03-001-12, July 6, 2012). The fix is the installation of a mass dampering kit on the rear cradle. It is a minor .7hr. job. See: http://www.sequentialtaillights.com/dodge/SB_PDF/TSB_LC_0300112.pdf
I guess if it has this whine we'd know? I haven't noticed anything but can't say I've paid attention. I guess I'll take a road trip this weekend.