It sounds like 4 wheel drive is trying to engage on its own.. Making a horrible sound like the front wheel is grinding and even going to fall off!! Is there a sensor that controls this?? I hardly ever use the 4 whee drive. I did not think I was going to make it home !!

 

hahaha, what year is it??? I know that when ford was first working out the electical 4x4 (early 90's), they sometimes, after time, use and wear, would disengage but not stay disengaged and eventually workthemselves back on...sorta...making that horrible griding noise you heard...its the hub on the 4x4...at least thats what it was in mine...to know more, you'd have to supply the year and model

 

If it is a 1999 or newer you may have a hub bearing going out. If it is grinding you may have ruined the brake caliper and bracket. Lots of $$$$$$$$$$$

 

I just changed the hubs on my '93 from automatic to manual because they were engaging/disengaging by themselves. A horrible grinding noise accompanied by a series of sharp jolts was the tell-tale sign. When I took the old hubs out they literally fell apart in my hands. I'd say if your truck is early/mid 90s.......the same thing has probably happened.