Driveline angles

RGAZ said
Nice, thanks. So from that video, my takeaway is if the phasing is correct and the angles are parallel, there is no vibration felt. If there is a small difference in parallel the vibration would be felt all the time and get worse the faster you drive. It would be constant and never come and go, right? I also would surmise that the vibration would be in phase with the speed of the driveshaft. (vibration cycle changes with speed of shaft).

This is good info, I always wondered why some people would immediately know its a driveline problem and not just alignment or something else. This makes sense.

Thanks,
RGAZ

Meh, sorta. There's a range of which you get no vibration. In other words, if it's "close enough" you're ok. That "close enough" varies so it's best to get it as close as you can. It has to have that range, because as you saw in the video Del posted, the driveline angle is constantly changing while the vehicle is in motion.