front end question

Richmond, VA
My 09 Vue FWD has started making a clicking sound when in reverse and moving with the wheels turning. When I back out of my driveway, which is on a steep hill I just put the trans into N and coast clicking. If I put it in R and keep the wheel straight then no clicking. In forward no clicking. What is the problem? I know very little about suspension/CV joints etc. Tomorrow I'm gonna look at the CV boots, etc but I want to know what to look for.