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What to check when feeling vibration over 75mph?

Discussion in 'A3/S3/Sportback (8P Chassis)' started by A3racer, Oct 16, 2010.

  1. A3racer
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    A3racer Never Follow

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    [Oct 16, 2010]
    Problem has been getting worse on my '06 A3 8P2 3.2 Quattro with 80,000 miles. I have already ruled out tires and wheels, spacers and brakes, axle and cv joints. The vibration seems to be coming from the engine and traveling down from transmission through the axle to the front right wheel. We put it up on a hoist with and without any wheels and you can see the drive train wobble. At about 75mph it looks like- and feels like- the wheel might just shake off the car. Initial inspection shows no broken motor mounts, but we haven't removed them yet. Any ideas? (Note there is no misfire present)
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  3. klik
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    klik Member

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    [Oct 16, 2010]
    flywheel, clutch assembly?
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  4. paddy
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    paddy Audi=No fault code, no idea

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    [Oct 16, 2010]
    I wonder if its transmiting back from a knackerd prop shaft UJ .. sounds like a balance issue without a doubt.
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  5. AudiMafia
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    AudiMafia Member

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    [Oct 16, 2010]
    The wheel bearings may also be going bad in the front end. Bad wheel bearings will cause vibration in the engine compartment, leading to a rougher ride, and usually a loud rubbing noise. Unrepaired, bad bearings will eventually cause your wheel to seperate from the axle and this damages the inner axle. If this should happen at high speed... the axle will dig down into the concrete and send the car airborne.
    #4
  6. liam_b
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    liam_b New Member

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    [Oct 16, 2010]
    at 80,000 miles I would start by replacing both of the rubber doughnut couplers in the propshaft, they're a common cause of rumble/wobble. Also since you did this 75mph 'spinup' test without wheels - did you get the chance to check all four drive shafts for bends? a slight bend in any one can cause severe wobble elsewhere due to the mis-tuning of designed out resonances.
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  7. A3chase
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    A3chase New Member

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    [Oct 16, 2010]
    the speed limit. ba doom dish...
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  8. A3racer
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    A3racer Never Follow

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    [Oct 16, 2010]
    Great replies. Thanks for your input. The front wheel bearings seem to be fine. I have replaced both rear bearings already. I have new axles and cv joints in front, but did not actually inspect all the other axles for vibration. (I sure wouldn't want to send my car airborne!) None of the other wheels have the wobble, only the front right closest to the transmission. I will have my mechanic check out the other compenents mentioned. Is there an easy or cheap way to diagnose the flywheel or prop shaft? I have the motor mounts ready to order, but it seems to me there is something causing the engine to wobble so much and I want to address that at the same time.
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  9. quattro7tdi
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    quattro7tdi New Member

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    [Oct 17, 2010]
    got the same issue would like to know what it is
    I have been told it could be the DMF is on its way out, hence the vibration a bit like an unbalanced wheel, which would come and go a certain engine speeds?
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  10. A3racer
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    A3racer Never Follow

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    [Oct 17, 2010]
    I'll let you know what I find out. I'm going to try to get in in tomorrow.
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  11. A3racer
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    A3racer Never Follow

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    [Oct 22, 2010]
    After checking everything my mechanic determined that my new spacers were not alligning the wheel perfectly because they lack the hub-centric centering feature. He re-alligned the wheel on the hub as carefully as he could and the vibration was gone. (Ugh!!!):banghead: He spent hours on it and didn't charge a dime because he had purchased and installed the spacers himself when the big brake kit was installed last year. New spacers with the hub-centric alligning feature will be ordered. Problem resolved.
    #10

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