I hope you can help me. First, let me start by saying that this is being written by a woman with absolutely no mechanical knowledge. We own a 2002 TB LTZ with approximately 180,000+ miles. We live 45 minutes outside of town so we put a lot of miles on a vehicle. This past winter we realized that our 4WD was not working when I got stuck during a snow storm. Lately when we drive the vehicle, there is what I can only describe as a grinding noise coming from under the hood. My husband says it sounds like a vibration, but it sounds more like metal-on-metal to me. It lasts about 2-3 seconds. It will make this noise about every 3 or 4 minutes, or it might just make the noise once or twice during our 45 minute commute - or it might not make it at all. There is no method to the madness other than it never makes this noise while in park or idling. Also, our 4WD switch light does not work. Sometimes when we start our TB all 4 lights come on and it makes a clicking noise. Obviously our Service 4WD light is on. Do you have any clue what could possibly be going on? Thank you.