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97 Sport 1100i driveshaft vibration

Discussion in 'Spine' started by Spaghetti Western, Jun 2, 2020.

  1. Spaghetti Western

    Spaghetti Western Just got it firing!

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    Greetings!

    I am chasing a harmonic (i.e. periodic) vibration felt through the seat and foot pegs that is drive line related - feels just like a car/truck that has a bad u-joint that is allowing the drive shaft to oscillate. It only occurs from 70 mph and up.

    After tear down I discovered that while the front u-joint is securely clamped to the trans output shaft the rear u-joint is not clamped down but is free to slide fore and aft on the rear drive input shaft. As such, it has a little play that allows it to rock on its axis.

    Since this is the most likely cause of the issue (yes, the u-joint yokes are correctly aligned/phased/installed according to the FSM) I want to tighten it down but I can't budge the socket head screws with a long arm Allen wrench in either direction.

    Does anyone know if the factory uses red Loctite on these?

    TIA
     
  2. scottmastrocinque

    scottmastrocinque Scott Mastrocinque GT Famiglia

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    MedicAndy is the guy you should private message.

    He has I think, 7 total 1100 Sports!
     
  3. Spaghetti Western

    Spaghetti Western Just got it firing!

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    Thanks!

    I see you are from Findlay; I grew up not far from there.
     
    scottmastrocinque likes this.
  4. V700Steve

    V700Steve High Miler GT di Razza Pura

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    All the exposed shafts I serviced had blue on them, many stuck allens. 1/2" breaker bar w/allen socket is the way to go.
     
  5. Spaghetti Western

    Spaghetti Western Just got it firing!

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    Ok, thanks. I'll give that a try.

    Do you know if applying a little heat to the yoke would soften the blue? I know that is the trick for red.
     
  6. V700Steve

    V700Steve High Miler GT di Razza Pura

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    Localized on the threaded coupler, careful there is a seal close by.
     
    john zibell likes this.
  7. Spaghetti Western

    Spaghetti Western Just got it firing!

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    Ok, got it apart using a 3/8" breaker bar, threads all cleaned up and test fit shows it gets real snug @39 NM (4 KGM) so might try a little tighter but am approaching the max.

    Assuming it is supposed to be clamped down, is it supposed to be spaced a little bit away from the snap ring on the drive input shaft?
     
  8. V700Steve

    V700Steve High Miler GT di Razza Pura

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    I can't remember if it's in that far against the snapring. You need to make sure the shaft has clearance to u-joint under all circumstances. The farther it is on shaft the closer the shaft is to rear u-joint.
     
  9. Spaghetti Western

    Spaghetti Western Just got it firing!

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    Of course, the FSM says nothing about that, but with it slid up against the snap ring the drive shaft swings far enough that the yoke attached to the drive shaft contacts either the rear drive input yoke or the u-joint shroud. In other words, it does not contact the rear drive input shaft when swinging in either direction.

    So that is where I positioned it. With fresh blue Loctite and clean threads when torqued to 39 Nm most of the slop was gone but it still would slide on the splines. Since the bolts are 12.9 I gritted my teeth and cranked the bolts down at 45 Nm and now it is tight.
     
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  10. V700Steve

    V700Steve High Miler GT di Razza Pura

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    Seems like a lot for it but tight works.
     
  11. Spaghetti Western

    Spaghetti Western Just got it firing!

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    Ok, finally got it all back together, did a test drive and the harmonic vibration is gone. Case closed.

    For the record, the zerks are all pointing in the same direction, as shown in the FSM, as this ensures correct phasing of the u-joint yokes.

    Thanks for the help!
     

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