GenIII humming in rear (not bearings)

[tlestan]

I have a 2004 Mountaineer AWD with the 4.6. I developed a humming noise from the rear of the vehicle last fall, but it was only at 65 and faster. It's progressed now and it does it all the time. I replaced the rear bearings, but no improvement. I dropped the rear driveshaft to change u-joints and noticed that if I push and pull the driveshaft on either side of the slip joint, there is a little play. Could a sloppy slipjoint cause a vibration? To diagnose, is it ok to drive a mile or two without the rear driveshaft, or will this hack up the rear diff? Thoughts?

 

[Number4]

To flat tow it, you'd have to disconnect the rear driveline.

 

[tlestan]

I'm taking that as it's ok to drive a bit without the rear shaft in place.