I know this thread is pretty old, but I've got an 04 Endeavor AWD that is making this noise, at least as you all describe it. It only starts over about 45 mph, sounds like it's coming from the engine compartment, and seems to oscillate as if it were a belt slipping and then slowly catching up again. I'm sure it's the prop shaft bearing you're describing, and I took it to a dealer last fall at 59000 miles. It made the noise for 3 hours from Grand Junction to Denver, CO, I dropped it off, the mechanic said he couldn't hear anything, sent me on my way, and it made the noise the whole way home again. Of course now, I'm at 65000 miles and my powertrain warranty has expired. Do I have any recourse on this? Other dealer in Denver now says it's $744 to do the repair, out of warranty. Help!