Had a loud knocking noise coming from front of car along with a scraping sound. Took it to a ford dealership, they said it was the transfer case. Replaced the transfer case as well as the front prop shaft because the shaft boot had ruptured and allowed dirt to get into the CV, ruining it. The noise is gone but the drive shaft fits VERY tight and there is now a severe vibration. Thought it may be the new transfer case or driveshaft... replaced the shaft with a new one and put the old transfer case back in so I could be sure that the new one wasnt the problem: the vibration remains along with the tight-fitting driveshaft. So all I can think of is it is either the new driveshaft (unlikely) or the front differential. I just dont know how the front diff could make the driveshaft fit so tight. I am at the end of my rope with this thing.. I never was a big Ford fan and now I am even less of one.