I have a new to me 86 F350 6.9. It is my first diesel, and also first 4x4. Ive just recently started driving the truck. Today there is a horrible squeeling noise at slow speeds, which turns into a high pitch noise at high speeds. The noise isn't always there. There are a couple of things that may have lead up to this. I got the truck stuck in a very deep mud hole. So deep I almost couldnt open the doors and had to have a bulldozer pull me out. Im sure mud got everywhere and inside everywhere. I also drove the truck about 200 miles with the hubs locked. Im new to 4x4, is this bad? At 85 I smelled something that smelled like fireworks and finally pulled over to manually unlock the hubs. Did I make the smell up? or could something be burning from the locked hubs? Today I also filled my bed with plywood, 2x4s and quick crete, the first heavy load Ive put in the truck. I hauled the load about 50 miles. At first I thought it was the front brakes completely worn, because the sound stops if I hit the brakes even if I just lightly touch the brakes. On the contrary, steering affects the noise. I know nothing about hubs or U joints. At first glance I couldnt even tell what kind of brakes the front has. Are they really drums? Sorry for being a noob!