Join Date: Aug 2011
Location: Oklahoma Panhandle
Does the grinding come from beneath you, or behind you. If it is behind you (near the rear wheel), it might be the rear splines. Unfortunately, one of the big issues with our bikes comes from improper lube of the rear splines on the drive shaft. This is a factory issue, and if not checked/remedied, could result in the symptoms you described.
Search the forums for 'spline lube' for lengthy discussions about this problem (and a lazy Nebraska farm boy).
2005 VN750 upwards of 14K (haven't looked lately)