When taking my foot off of the accelerator, I get an intermittent "clunk" which sounds like something either engaging or disengaging on my 1999 F150 (4.6 L). The dealer service manager says he believes it's the normal backlash in the transfer case and I shouldn't worry about it. I've seen other threads similiar to mine in this forum, but I've never seen a resolution. Anybody ever get this corrected?