When I slow to a stop, I hear a real quiet ticking that slows with speed, starting at around 5 or so mph, and I can roll at 0-5 mph and hear it going tick tick tick tick, and depending on how fast I roll, the ticking is faster or slower until I stop. When I put it in 4wd, the ticking stops all together, and then I'll put it in 2wd while still rolling and it starts again. It seems to dissapear past 10mph, or else its too inaudible. Any ideas on what to look at or what it could be? It just started all the sudden a few hundred miles ago. I have a 2002 GMC Sierra z71 with 40,000 miles. Thanks alot