[LPete]

Originally Posted by Brett_ty

I have read a few guys here that stated to "rotate driveline 180, that will put you back in "phase" if your out of it and vibration will go away" (or something to that affect).

1) Is that simply disconnecting rear driveling u-joint from the rear pinion and rotating it there? (leaving the slip in the transmission)
or
2) Removing the driveline from the car pressing the u-joints out and swapping the slip yoke to the other end (the end that was attached to the rear).

And
What does that mean "driveline out of phase?"

#1 is correct. The driveshaft and pinion flange are marked at the factory, and when the driveshaft is installed correctly the heavy spot on the pinion/pinion flange ends up 180 degrees from the heavy spot on the driveshaft, canceling slight out-of-balance vibration. It may help to rotate the driveshaft in the pinion flange to see what happens.

Out-of-phase is different:
Simple U-joints cause the driveshaft to accelerate and decelerate slightly with every revolution. U-joints are "in phase" if they're installed so the crosses in both joints are in the same plane, canceling out the acceleration/deceleration (which can cause vibration). The only way they can be out of phase normally is if there's a slip yoke in the middle of the driveshaft that can be assembled with the joints out of phase (the yokes not in the same plane). I suppose a yoke could be welded on the driveshaft tube out of phase, but that doesn't seem likely. Rotating the driveshaft in the pinion flange doesn't change u-joint phase.

Here's a website that explains this: http://www.4crawler.com/4x4/CheapTri....shtml#Phasing

[Brett_ty]

[QUOTE=LPete]#1 is correct. The driveshaft and pinion flange are marked at the factory, and when the driveshaft is installed correctly the heavy spot on the pinion/pinion flange ends up 180 degrees from the heavy spot on the driveshaft, canceling slight out-of-balance vibration. It may help to rotate the driveshaft in the pinion flange to see what happens.


Thanks
one more question, so since both the rear and the driveshaft are new (currie/Inland Empire) and from diff. companys, supppose I had it installed correctly, I am guessing that if I do the 180 swap I should get a wicked vibration.
There is an aluminum weight that is welded on the driveshaft towards the pinion end (I suppose that it was from balancing)..So I am guessing that is the "heavy spot." How can you tell on the currie rear pinion flange...what am I looking for there to indicate the "heavy end?"
Thanks again