On my last truck, I had a grinding noise coming from one of the front wheels. It would start at about 20 mph and get a little louder up to around 45 mph, then it would disappear. It would also get louder when I took turns in one direction in the 20-45 mph range and disappear when I turned the other direction in the speed range. It turned out to be a wheel bearing. It's pretty easy to diagnose, just raise the front end (either the whole front end or each corner separately) and spin the wheel in both directions. If it's the bearing, it will make noise, like a grinding noise. It also doesn't spin that freely. If it's not the bearing, it will spin freely and be quiet. On my last truck (an '02 GMC), repair was pretty easy. The bearing came pre-installed in a hub assembly, so all I had to do was change out the hub. Took just a couple hours from beginning the initial diagnosis to completion (time included a trip to the parts store for the hub assembly).