1999 Sport with about 230k. Bought it a year ago for my son who is close to getting his license, so It's only been driven maybe a thousand miles since I bought it. Out of nowhere recently, a pretty loud rotational noise has started in the front driveline somewhere, and I'm not sure where to start. It begins at around 15 mph and gets less noticeable if I go faster. When slowing to a stop the noise gets worse and slower with slower wheel rotation (or maybe slower drive shaft rotation). Finally, just as it comes to a stop it sounds like something is really binding or about to break with a very loud clunking sound. **Possible clue**-> It seems to go away if I throw it in 4-Hi. I've jacked it up and spun the tires by hand, and cannot reproduce it, but I don't know if I'm able to get the tires moving fast enough to get the problem kicked off. I checked the diff oil this morning and it's full. Ideas on what to check?