Actually I'm talking about the small arrows I mentioned a while back which are imprinted at the mating ends of the front and back sections of a 50.8mm driveshafts (from an '84) that I was planning to use. When I assembled the shaft with these two markings pointed directly at one another (--> <--) the yokes looked to be in phase. I seemed obvious that they were index marks for this purpose but I didn't know for sure and no one else seems to have ever seen them, I suppose because they're small and usually covered with road grime. The manuals don't mention them, to my knowledge.

Since I hadn't been careful enough to mark the two parts when I took the shaft off of the donor car I used the arrows as a guide when installing the shaft in my current car. The result was no vibration from the driveshaft. I accidentally did get this very shaft out 180 degrees of phase once when I was still driving the car that it came from and the vibration was pronounced.

I don't know when they began using these markings or if they're on the smaller diameter driveshaft. I should have found out about this because I have two of those smaller shafts in the basement but I've been too lazy too look. I will examine them.

Be on the safe side though. Mark your driveshaft before you take it off. But if you forget or if you get confused look for those arrows. If you see them, line it up that way.
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'80 DL 2 dr