I pulled the shaft off for a good sinpection... no obvious problems. The slip yoke does have some black scarring on the surface up at top by the u-joint, but it's stil smooth and feels fine once cleaned. I can only asume this is from a combo of exposure and grese ground in.
Cleaned and lubed the yoke and splines, made sure there was lot of grease in/around the DS everywhere. Also checked both u-joints, by hand they "feel" smooth rolling around, and have plenty of greae 9at least when I aply the gun, grease comes back out the fitting0
Unfortunately, the problem persists. It is a little quieter now, but not by much.
I do wonder if possibly the upper u-joint has a bad bearing or something in it, and it appears only at high revolutions and when only very slight torque applied (no noise heard with any throttle).
Is there any way to tell, w/o jut replacing it? i rottated it around by hand and didn't feeling any sticking or aything.
Note also the angle is pretty minor, total lift only about 2.5".