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Old 09-05-2017, 12:33 AM   #1
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Join Date: Apr 2015
Location: Gallatin, MO
Posts: 245
Correct clock/phasing/orientation of yokes on '66 C20 2 piece driveshaft

Does anyone have a picture of a correctly assembled 2 piece driveshaft for a '66 C20? Or any input on the somewhat long story below? It has a th400 and HO52, just fyi.

I'm chasing a vibration, and the brand new set of Cokers i just put on didn't fix it... or the shop didnt balance them correctly. So, I decided to replace all the u joints and center bearing on my driveshaft to rule it out. When I put it back together I realized I hadn't marked the position of the yoke that bolts in front of the center bearing, and now the two shaft halves (which I did mark) didn't line up like they used to. Which is weird, because it felt like the yoke in question would only fit on the splines one way.

Afterward, I took the whole assembly to a shop in KC to be balanced, and the guy told me I had the center yoke clocked wrong, because it's supposed to be aligned with the one at the other end. Ok, makes sense. So he doubles the damn price and says he will rotate it for me. He also told me in the same breath that the splines are such that it can only be installed one way. (If that's the case, how could I have got it on wrong!?)

So I pick it up the next day and the center yoke is still crooked, but the guy insists he took it off and turned it. He says "apparently this one was designed to be a spline off". Original weights have not been touched, and I have no real proof he did anything. He said the way I had the yoke, it vibrated, but once he allegedly turned it, he ran it up to 3k rpm and it was balanced fine. No idea, this is just what he told me.

The point is, I'm trying to verify if anything he said is true, because the rear end still vibrates a little (jacked up with wheels removed) and I can't make any sense of my manual ('63 service manual). Specifications table on 15-5 lists correct phasing, but I can't figure out which applies to me. I'll attach a pic. Looks like some yokes are supposed to be aligned, some are supposed to be "x" number of splines out of plane.

My hope is that I can verify 100% the driveshaft is assembled correctly, and the yahoo at the shop was telling the truth, so that I can take it back to the tire shop and tell them definitively which tires to check/redo.

I know there's a rear tire issue because I jacked each one up this evening and run it to about 25 mph and they shake (one side worse than the other). In the process I pulled each wheel off and ran it with just the bare hubs/drums, which is when I noticed it still has a vibration, although not nearly as strong.

Sorry for the long winded post. Any help and or pics would be much appreciated.
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