I've been reading through other posts and have found a few items that are somewhat similar but I would appreciate any suggestions you might have on this one...
I've got a 99 Mountaineer V8 AWD with 68k. About a month ago I started noticing a slight "grinding" noise when turning at low speeds. I almost immediately thought it sounded like my old 92 Explorer when I had the 4x4 engaged. Since then, I also developed the infamous EGR valve/DPFE sensor problem (replacing the DPFE sensor solved it, by the way)--so for about 2-3 weeks it was driving horrible. In the middle of that fiasco, the grinding noise seemed to have gotten more constant and can be detected when speeding up or slowing down. And now, the ABS Light is on full-time. I also noticing a squeeling of tires sometimes when I'm making a tight turn in forward or reverse.

My question... Is the power distribution in the AWD somehow managed by the brake speed sensors? I've read quite a few posts that the ABS light often indicates that one of these sensors is bad. I removed the rear speed sensor to try to test (I got no reading on the resistance test). However, logically if that sensor was bad then shouldn't my speedometer also be malfunctioning?

Please let me know if there is anyone who's been through a similar experience. Thanks for any help you may have!

I can tell you it's probably not your transfer case, as it is only managed by the laws of physics, no computers involved.

If you hear a grinding noise along with your ABS light being on, it could be a sign of one of your hub assemblies starting to fail that has thrown your ABS sensor out of alignment.

Is the grinding coming for the front end? Is the tire squealing?

It definitely feels like it's coming from the front-end. The grinding started before the ABS light ever came on. I only get tire squeeling intermittently, but it is definitely something I never noticed before all this started happening.

check your CV joints and your brake pads.

My X has had this and it was my brakes. I still have another sound which I know is my passenger side CV joint.

Thanks for the info! I will check the pads and inspect the CV joint--I will post back once I do the service...

I've got new information (and confusion)--hoping you've got some ideas...

I discovered that an ex. warranty covered the rear speed sensor and had it replaced--the ABS light is now gone!

While it was at the dealer, I had them check on the vibration through the floorboard and gave them the information that it was more pronounced as I was turning, especially at low speeds. They said they inspected the steering, joints, etc. and found no problems.

Since then (about a week ago), the noise has now come to include an occasional brief grinding while accelerating, most noticable when accelerating from stop into a turn. The grinding can be felt through the floorboard, brake pedal, etc.

I changed the transfer case fluid over the weekend and did not notice any metal or other contaminents. The grinding feels related to the vibration/whirring and I would take that as a sign that it's getting worse and not a part of my imagination as the dealer seems to think.

Does this still sound like a CV joint? Is there anything I can inspect to further narrow this down so I know where to have them look?

Thanks!