Rick,
Take the whole driveshaft and bearing to a driveline shop and they can validate the phasing as well as balance. It may cost you about $100 if they need to balance it.
The two piece driveshafts are splined together in the center by the bearing. If you get the front and rear section off by as much as one spline, you will have driveshaft issues. IF you have a perfectly level concrete floor, you can use a few steel blocks. Start at the front, block up the u-joint on an end cap, make sure it is square to the floor. Then the next joint (same shaft) should sit perfectly flush on the next block. Then the rear shaft joints should also sit perfectly flush on the last 2 blocks. If the rear shaft does not sit flush that indicates you are off a spline on on the bearing support and slider.
While you have the shaft out, check the U-joints to see if you have one that is brinnelled or frozen.
Also, if you changed springs, axle mounts, or other rear suspension components, you may have a rear pinion angle issue, however this is a remote possibility.
Scott
