I have a 95 f150 4wd 5.0 automatic w/ 60k miles. While driving a couple months ago a loud clicking noise like playing cards in a bicycle wheel starting coming from the front end. I pulled over and had my buddy drive forward slowly while I looked underneath and I saw that the front driveshaft was spinning even though the truck was not in 4wd. So I put it in 4wd then back into 2wd and it stopped clicking. This happened 5-6 more times over the last couple months then the other day while on the highway the same thing happened only at 80mph the truck is so loud I didn't notice right away and by the time I pulled over the clicking turned into a grinding and the front differential was smoking. Now when I put it in 4wd a very loud grinding noise comes from the front end. What is happening? How much damage did it do? Any help would be appreciated. Thank you.

 

I took it to my mechanic, the front differential was destroyed, he replaced that, converted it to manual hubs, and replaced the u-joints. Its good as new, no more ratcheting noise from the front end.