Weird Vibration at 2500 RPM's and above

1) Will the vibration occur at rest w/the trans in neutral & the RPM's in the offending range?
2) Generally a bent driveshaft won't unbend itself or stop vibrating popping the trans out of & back into gear, nor simply loading it.
3) If You grab the installed prop-shaft at the front, how much can You move it up & down?