I had my pinion seal replaced last week by a ford dealer. They also said I needed the flange that the shaft bolts to. Well now my truck has a weird scraping kinda noise when I slow down and when I first take off. It has no other noises while driving at higher speeds it still seems normal. It just makes the noise when slowing down and taking off. Did they cause somthing because it was fine before they made the repair. This is why I took it to them because I was afraid of somthing like this happing if I replaced the seal myself. I am taking the truck on a trip in two weeks so I need to get this figured out. I am sure they will say they did not do anything and charge me an arm and a leg to fix it.

I have tracked the noise down to the drivers side. You can here it while driving but if riding in the passenger seat you can hardly hear it. I jacked the truck up and ran it but it will not do it while jacked up. Only does it while driving. I know its not the brakes its not that kinda sound. Sombody please help its driving me nuts.

 

Well the diff is pretty much in the center of the truck, so any noise coming from it should be heard the same from the passenger side as the driver's.

You said it's not your brakes, and I trust you know what you're talking about, but I would give it one more look. It could be your front left caliper is sticking or the rotor and pad are completely worn down and metal is grinding on metal.

I just can't think of a differential problem that would cause that. Check and see if you have any gear oil running down the sidewall of your back tires or puddling in the rims.