I have had my 2004 F350 for 5 years and 44,000 miles now with no major problems. Today I took it to go to a doctors appointment. I made it almost all the way there with no problems. I got to a stoplight and went to make a left turn. While I was making the turn I heard a loud crack that happened twice and shook the whole truck. At first I thought the car next to me in the turn hit me, but he was not near me. It was only maybe 25 yards to the next stoplight. When it turned green I went straight. As I was accelerating it was cracking in the rear like crazy. I was in the right lane and could not pull over. I turned at the next intersection and the noise got relly loud and sounded like gears grinding. At first I thought it might have been a rock in could in a caliper. Before I could pull over it went away. I only had a block to go to the doctor so I continued. I called my Dad to come get me because I thought I would get it towed. I took him for a spin in it and it did it once quietly and then never did it. He followed me home and it only made the noise once in 15 miles. I got it home and felt the punkin and it was hot. I do not know how hot these get. I then jacked the truck up so that both wheels were off the ground. It has a factory limited slip so I could not turn the wheels since it was in park. I put the truck in neutral and it seems very hard to turn the wheels, especially if I turn them in the reverse direction. I could hear the passenger side caliper slightly against the disc but from all the driving it was not hot. I figured it would be hot of it was rubbing hard. My question is: Should it be hard to turn the wheels if the truck is in neutral? My dad has a ranger and I know it is a smaller truck, but his wheels turn very easy. Thanks.