Yesterday was spent replacing U-Joints and the center bearing on my '74 F250 Camper Special. I marked the original position of the driveshaft before removing them, but noted that the yokes on the rear shaft did not align with the yoke on the front shaft right off the transmission (C6 Automatic). These had clearly been replaced before, apparent by minor damage to the yokes from banging them out with a hammer at some point. I am not certain at all that the previous mechanic (probably the owner) bothered to install the driveshaft the same way it came out and would be leaning towards the idea that it was more random.

So the question is, do the yokes need to line up? Or is the fact that there is a center support bearing a reason to not worry so much about whether they align, just whether they are balanced as a unit? If I were doing it from scratch, I would align the yokes, then have them balanced.

There isn't really any noticeable vibration from the driveshafts, but I have only driven them up to about 50 mph. I have a 3.73 rear end, so that probably puts the shaft rotation at around 2200 rpms. It is unlikely that I will drive more than about 65 mph any time soon (there is nowhere in Washington that you can go over 70 mph), but may eventually get over to Montana again and probably need to be able to go 70 mph without worrying about the driveshafts. What would you do knowing that they may not have been in balance in the first place, and the yokes were not in alignment?

Thanks for any thoughts.

 

Google driveshaft "phasing", better explanation there. I would say yes line up all the yokes, that way you can go 70 and be vibration free.

 

I'd phase the driveshaft as a matter of good practice. Plus
phasing will reduce the possibility of a vibration as the u joints wear..and the center bearing will last longer very because it doesn't have to compensate for the mismatched phasing.

 

Scroll down here, there is an illustration from the '68 shop manual.

two piece drive shaft questions - The FORDification.com Forums

More here, including a Spicer link that will keep you up all night:

http://www.powerstrokenation.com/for...on-ccsb-2.html

 

Thanks guys! That pretty much confirms what I thought would be the best way to go. I'm guessing the PO didn't realize that the shaft should be marked before you remove it to keep it in balance, and then didn't further realize that the yokes should line up. I'll get them aligned, then if there still seems to be any vibration, I'll get the shaft balanced as an assembly.