1999 Ford f-150 4x4 manual loud clunk while running 60 mph. Engine died
and pulled over to side of road. Could not see anything wrond after inspecting
and engine restarted. Could not move but able to shift into 4x4 and was able to limp home (40 miles). After blocking wheels, shifted out of 4x4 and put into 1st gear and could see drive shaft turning and making no noise.
Suspecting u-joints to be the problem...anyone with any ideas????thanks.....

 

by your description it sounds like the rear end is shot.

did you still have all 4 wheels on the ground when you put it in gear and saw the driveshaft spinning?

every time i've heard of u-joints going they make lots of noise when they turn.

 

If the u joint failed, you would have bigger problems, because the only way the shaft would spin freely is if it disconnected itself from the axle. Your problem sounds like the rear ring and pinion broke allowing the driveshaft to turn with no sounds.