The timing is okay? If it slipped wouldn’t you get erroneous readings?
Slipping the car into neutral at speed and in the know vibration range almost eliminates the vibration so that eliminates the driveshaft as it’s is still spinning at the same rate, as are the u joints, granted the rear is a tiny tiny bit loose and will get changed right away anyway. I can’t see how a noisy diff would cause this and again is still spinning at the same rate when slipped into neutral?
tail shaft bushing is okay and the yoke engages the whole length of the bushing, although I would like to see about 1” more engagement on the slip yoke.
talking out loud is great and I hope to find a good idea I haven’t thought of that may lead towards a fix.
