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What's phaseing or lineing up your u-joints?

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by BobK, Sep 3, 2001.

  1. BobK

    BobK 1/2 ton status

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    What\'s phaseing or lineing up your u-joints?

    I've heard of guys saying to make sure your u-joints are in phase or lined up.What the heck does that mean?


    <font color=green>BobK<font color=green>
     
  2. ErikH

    ErikH 1/2 ton status

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    Re: What\'s phaseing or lineing up your u-joints?

    I've also read about this... And to the best of my knowledge, phasing has to do with making sure the angles between the shaft and the yokes (on the diff and xfer case) are the same. In other words, if your xfer case is parallel to the ground, which means your xfer case yoke is parallel to the ground, then to keep things in phase, your differential yoke needs to be parallel to the ground. Or if your xfer case is tilted downward at let's say 3 degrees, then your differential should be shimmed 3 degrees upward.

    If one angle is more than than the other, you'll get a vibration, as the u-joints oscilations need to be the same so they can cancel each other out. My mildly lifted Blazer vibrates because the diff is tilted up toward the xfer case, and that angle is less than the angle between the shaft and the xfer case yoke. I can either drop my xfer case an inch, or I can install a CV-joint type shaft that can accomodate greater angles without vibration. I don't have the time or money to tackle either remedy.

    If anyone has a better interpretation, please correct me.
     
  3. Chris Demartini

    Chris Demartini 1/2 ton status

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    Re: What\'s phaseing or lineing up your u-joints?

    <font color=blue>Phasing is when you make sure the u-joint caps at one end of the shaft are in line with the caps on the other end. If they're not, it'll vibe no matter what angle its at.</font color=blue>
     
  4. ErikH

    ErikH 1/2 ton status

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    Re: What\'s phaseing or lineing up your u-joints?

    Ahhhh... But I have a question... On my driveshaft, on which the shaft yokes are welded to each end, it's essentially impossible to misalign the u-joints. The u-joints (and therefore shaft) can only be installed one way... Or am I missing something?
     
  5. bitchin4x4

    bitchin4x4 1/2 ton status

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    Re: What\'s phaseing or lineing up your u-joints?

    fyi: its not the best solution but its cheap and easy and it only cost $10. you can shim your rear end up to 8 degrees, after that I believe you need to reweld your spring perches.

    If it ain't broke, break it!
     
  6. bitchin4x4

    bitchin4x4 1/2 ton status

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    Re: What\'s phaseing or lineing up your u-joints?

    the shaft is usually balanced I believe, stock that is. but if you had a drive shaft custom made it is possible for one of the loops which hold the caps on your ujoint to be off, thus causing vibrations.

    my driveshaft makes so much noise it aint funny! ;0)

    If it ain't broke, break it!
     
  7. Chris Demartini

    Chris Demartini 1/2 ton status

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    Re: What\'s phaseing or lineing up your u-joints?

    <font color=blue>The driveshaft comes apart at the slip joint, this is how it can become misaligned (someone puts it back together wrong).</font color=blue>
     
  8. Steve_Chin

    Steve_Chin 1/2 ton status

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    Re: What\'s phaseing or lineing up your u-joints?

    To clarify a little further, the yokes on the driveshaft need to align with each other so that the centerlines of the bores in the yokes are parallel with each other. If they are off more than a few degrees, you will have a vibration.

    There's another phenomenon known as "critical speed" of a driveshaft. Generally, a smaller diameter driveshaft will have a lower critical speed than a larger one (depending on materials and construction techniques). Half of the critical speed is generally considered the comfort zone for that shaft, although it's common to rev them up to their critical speed.
     

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