So I have been down a car for a week or so and borrowed my old Disco from my dad (sold it to him a few years ago). It has all of a sudden developed a bad driveline vibration between 30-45 mph. I thought for sure it was the rear drive shaft because when I got under it to look, the 4bolts holding the flange to the driveline brake were totally lose. So I put some lock tight on them and cranked them down. But it still vibering, and it makes a weird squeaking sound or a chirp. Any ideas? Could it be the front shaft centering kit that's bad? I grabbed it and tried moving it around to see if it had any play but it feels rock solid.