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Please tell me this is normal... (Shaft Play)

Discussion in 'XJ Technical Chat' started by BmwE30, May 19, 2013.

  1. BmwE30

    BmwE30 Member

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    Been getting a nasty vibration(from the rear) in 4 & 5th gear around 45-50mph. I figured it would be the U-joint so I jumped right in. For the record, final drive gear has new motul 75w90 fluid, the u-joint was found to have ZERO play, shocks are new, and no bolts or misc nonsense was found to be loose. everything looked pristine inside until I decided to check the output shaft play. This is my first XJ and I'm still learning, but this seems pretty excessive. 1980 XJ650 with roughly 17-18k miles....

    http://www.youtube.com/watch?v=pbNJ6nViZEk
    [YOUTUBE]http://www.youtube.com/watch?v=pbNJ6nViZEk[/YOUTUBE]


    [​IMG]
     
    BmwE30, May 19, 2013
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  2. BmwE30

    BmwE30 Member

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    Also the tires have 3 consecutive seasons as I ride year round. It's not one of those "dead spot" vibrations. It's a harmonic vibration but more violent than the 60mph vibration. Comes and goes away at speed enough to shake my headlight beam pattern enough that I can not only feel it in my seat but see it as well. Bike runs completely fine otherwise. Forks were rebuilt as well when I did the 750 front end swap
     
    BmwE30, May 19, 2013
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  3. MiCarl

    MiCarl Active Member

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    Hard to say from the video if there is excess lash or not. With bevel gear sets excess lash tends to result in a growl that is load dependent. Does the problem change if you accelerate vs. coast?
     
    MiCarl, May 19, 2013
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  4. TIMEtoRIDE

    TIMEtoRIDE Active Member

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    You removed the swingarm to chase-down this vibration??

    Did you check the tire balance at home, using 2 chairs ??
    Tires will make all kinds of weird "harmonic" noises and sensations.
     
    TIMEtoRIDE, May 19, 2013
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  5. BmwE30

    BmwE30 Member

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    Not sure if that's sarcasm, but it only took 40 minutes to get the swingarm apart. As I stated, I planned to replace the u-joint since it seemed the most realistic culprit. Regardless, ill have the rear tire rebalanced even though it was just done 800 miles ago.

    MiCarl, the symptom is less noticeable under load through turns as well as down straight roads. It is not apparent with the clutch depress and coasting. It is most noticeable while cruising steady at 45-50mph.

    Getting on/off throttle feels a bit jerky, like a worn out motor/trans mount on 4 wheels. This happens in every gear.
     
    BmwE30, May 19, 2013
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