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Banging and vibration in drivetrain

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by d215yq, Jul 16, 2020.

  1. OP
    d215yq

    d215yq Senior Member

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    Thanks for the responses. I went back and he said it could be the rear wheels as he's sure he lined it up properly.

    I said that would be very unlikely (unless he touched the wheels too) and he agreed so will look next week (he's busy and said he wouldn't fit it in as an emergency like before as the car is safe to drive).

    Which sounds fair enough, I assume it's OK to drive for a while like this?

    He did mention something about being able to slide the position of the centre bearing slightly or something similar. Does this sound feasible?
     
  2. oigle

    oigle Senior Member

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    If the centre bearing is positioned outside of a straight line from back of gearbox to diff, you will get issues as the uni joint can only accept an angle change in one direction - obviously up and down in normal use. If it has to also go sideways it will vibrate.
     
  3. M80

    M80 Senior Member

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    I've read previous to this thread that re installing the prop 180 degrees can cause the vibes, therefore marking prior to removal becomes advantageous.

    But a prop is balanced to rotate without vibes.

    What I struggle to understand with this is that when new is there a 50% chance the prop will be installed wrongly?
    When fitting a replacement 2nd hand prop is there no chance of this running smoothly?

    Most of you clearly understand this need for this, what am I missing?
     
  4. LostKiwi

    LostKiwi Senior Member

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    A propshaft is factory balanced in its entirety (gearbox end to diff end). If you pull it apart then to maintain the balance you need to get the alignment the same as it was when originally balanced (or pay to have it balanced again). On some props there are markings showing correct alignment. Makes it easy to see if it's been reassembled correctly.
    Similarly any replacement propshaft will be pre-balanced from new as an assembly.
     
  5. OP
    d215yq

    d215yq Senior Member

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    As an update the guy looked over it again. Showed me it was lined up and also the balancing weight stuck on with silicone which he said was not normal. It wasn't him as he commented on that before he did the work too.

    He says maybe the previous centre bearing was deliberately not tightened to avoid the vibration as the volts were loctited not fully tightened. He did offer to trial and error some stuff but would need the car for a week and it may end up needing taking off the whole thing and sent to the other side of spain for rebalancing.

    He said annoyance aside these propshaft *never* break and it's safe so I've decided as I have a property to do up in the middle of nowhere and can't leave him the car I'll add it to the list of characteristics and be done with it for now.

    Fwiw when turning right and/or its loaded with 300kg of tiles/cement the vibration is less... There's also a similar but much less pronounced vibration at 30-35 as well...
     
  6. oigle

    oigle Senior Member

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    Did he try rotating the shaft 90 degrees where connected to diff as I suggested. Easy to do and worth trying.
     
    matthew k likes this.
  7. OP
    d215yq

    d215yq Senior Member

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    Would that be by rotating the rubber coupling? I think the coupling allows only 120 degree rotation as it's hexagonal?

    But no, he didn't do anything. Showed me it was lined up and done correctly so he can try things if I give him the car for a while which isn't possible at the moment...
     
  8. oigle

    oigle Senior Member

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    NO. I'm talking about the rear end of the drive shaft where it couples with the diff. The 4 bolt uni joint can be reversed by 180°
     
  9. OP
    d215yq

    d215yq Senior Member

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    I'm not an expert but to me it it looks like the flexi disc from prop shaft to diff can only be changed 120 degrees as it has 3 points each (so 6 in total)- As i understand it he didn't touch that anyway, just took the front disc off (20) removed the front half of prop shaft (1a), replaced the mount (7) and then put it back lined up as before. His suggestion was the bolt attaching 7 to the car was not fitted tight before so as to avoid the vibration?

    Are you suggesting that the uni joint in the middle of the prop shaft could be switched 180 degrees?


    Drive Shaft.jpg
     
  10. oigle

    oigle Senior Member

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    Sorry mate. Assumed the driveshaft would be like most "normal" cars with another uni at rear where the flexi disc is situated. From what you have said, I can't see how it could be reassembled wrongly provided the shaft 1a was lined up with shaft 2 as it was originally.
    Don't suppose the flexi discs are getting a little tired?
     
  11. OP
    d215yq

    d215yq Senior Member

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    No worries! I'm sure the flexidiscs arent perfect but it was fine before. I'm thinking it's either been put back wrong, the weight has been moved as it was siliconed on or it was just wrong and not tightened to hide it.

    Either way it's not too critical as the drives I'm doing now between my house and city flat are motorway and country road... Above or below the problem zone... Just 2km of roadworks where it's a problem so I can't be doing without a car for a week for only that... Will update here if I do get it fixed/investigated at a more convenient time in the future...
     

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