Problem with 4X4 Please Help

[2005powerstroke]

I tried to engage the 4X4 today and no power to the front wheels, front drive shaft does spin but still no power. the lights on the dash stay solid lit and don't flash as if there was an error if I'm remembering correctly.

Could it be the selector hubs are shot or does this sound like an internal front end is trashed.

2005 f-250
171,000 miles
Edge Tuner in towing mode. I get on it in 2WD but am easy on it when in 4WD.
Worked fine all last winter.

[NYC F-350]

Try locking the hubs in manually. If that works, you could just have a simple vacuum leak somewhere.