I'm having the same whinning sound coming from the rear while I'm accelerating and holding at that speed. mainly between 30-70mph. but as soon as I take my foot off the pedal as in for instance, going downhill or leveling off, it stops!!! only difference is it's my wife's 2004 Expedition NBX w/Autotrac. I hope the Lariat 4X4 I ordered don't have the same problem