Bad U-Joint? - Low Growl

[98valkryder]

My 1998 Tourer, 63,000 mi, has developed what I can best describe as a low growl coming from the center to forward-of-center of the bike.  The vibration travels up through the frame and is best felt in both handgrips.  This growl is most noticeable from 35mph to 65mph.  At higher speed it seems to smooth out.  Though continual, the intensity is not constant.  That is it "feels" similar to riding on a deteriorating rear wheel bearing set where the individual bearings are deteriorating at a different rate.
There is no grinding or schreeching... YET.

Both rear wheel bearings have been changed [running a CT].  The RF wheel bearing was replaced recently during tire change.

Any and all suggestions as the source of this problem greatly appreciated.

[Bone]

Replaced the U-joint in my 98 Tourer at 95k. miles. It started making a noise from the same area.
If you do your own wrenching pull it apart and check. Breaking down away from home means a tow or
a long wait at a shop trying to get parts. Tried pulling the boot back on the driveshaft but couldn't tell
the condition of the joint. Glad I didn't wait it was bad.
Posted a picture I believe of the joint.

Found the pictures
http://www.valkyrieforum.com/bbs/index.php/topic,42406.0.html

[Michvalk]

If it were me, I would pull everything down and inspect. Usually a low growl is a wheel bearing, but could be anywhere in the drive train. Once you have the rear wheel off, it's easy to pull the rest and look them over. Make sure you look at the pinion cup too as well.

[Daniel Meyer]

Pull it down and check it all out. Bearings, pinion cup, u-joint. I'm going to guess pinion cup.