Driveline vibration out of now where! Help!

In neutral, the output-shaft should spin fairly freely in the "normal" direction with almost no noise; just the noise of the slipping sprag; Kind of a squeak/creak that should be obvious..
But in the opposite direction the sprag will lock up and spin the low drum. The squeak will now be gone, and drag will be increased as the clutch plates will be dragging due to the sungear being involved, and the bands may drag as well. This increased drag is quite pronounced.
Edit: this is normal