The phasing of modern [last 30 years!!] triple joint tailshafts is a real drama. Many such as Holden Commodore always have a light 'whip' at low speeds under accelaration. Damned annoying. Most others do not do it,,, until everything gets old and tired
This does truly still confuse me. Even just a std tailshaft which all of us take for granted.
As does universal joints, simple but complex! That and balancing tailshafts, something many places cannot get right. Yet others can be machined off and shortened with no viabration issues.
Uni joints are not uni joints though. Some cheap ones seem to bind at high speed. Having suffered horrendous vibes at over 150 mph [race car] the brand name unis were replaced with high performance Spicer ones, shaft balanced [hardly needed it so they said] and no viabrations at all. Tested to about 175mph. In this instance I will reccomend Spicer for balancing whole heartedly.
Interestingly I was told that having the shaft dead straight at ride height is not a good idea. The rollers dont roll in the trunnions and the uni will get roller marks in the cross at a fairly short service life. In my case I just adjusted the nose of the diff down,which helps hook it up at low speed anyway, not so easy in most cars. This was because the pinion is so low in a 9" diff in comparison to the GM pinion it straightened out the angle. On my vehicle.