The only problem I have with my 28-300mm and from new, is a loud piezo noise whilst it focuses. When I first had the lens I thought it was faulty and sent it back to Nikon who returned with no fault found. Although my lens is evidentially exceptional for noise compared to other 28-300's Nikon finally told me that the noise was the piezo component of the AF-S motor. I've had the lens 18 months and apart from the noise it works excellently, it's annoying though. I do keep Nikons letter quoting the problem.
As I've never had this noise before, I can only conclude that is on fact the result of a lower grade motor as I described in my last post. I discussed this in a forum post here at the time, but it would appear my lens is a one off.