Bad vibes!
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Thread: Bad vibes!

  1. #1
    Fellow Frogger! 505 to the max's Avatar
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    Default Bad vibes!

    My 505 has a worked GTi motor and it's last dyno readout was 115 rwhp. When it 'comes on cam' at 3000 - 3100rpm it pulls strongly right through to about 6000 however, at about 4400 - 4500 (peak torque according to the dyno printout) it developes a strong and particularly noisy vibration in the drivetrain, the vibrations being most evident when holding onto the gearstick. The noises seem to trail off towards redline. As it will be wearing a turbo in a few weeks I want to pinpoint this (possible) problem so that I don't break anything but don't know what could be causing this. Has anyone experienced this before in a 505/504?

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  2. #2
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    Sounds like imbalance in the tail shaft, but this would mean it would be speed related - is it only evident at 4500rpm in a particular gear?

  3. #3
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    These engines do vibrate a lot as they are large for an all alloy block, I don't know of any other alloy 4 cylinder motors this big.
    What was it like before you did the modifications?
    Graham

    Quote Originally Posted by 505 to the max
    My 505 has a worked GTi motor and it's last dyno readout was 115 rwhp. When it 'comes on cam' at 3000 - 3100rpm it pulls strongly right through to about 6000 however, at about 4400 - 4500 (peak torque according to the dyno printout) it developes a strong and particularly noisy vibration in the drivetrain, the vibrations being most evident when holding onto the gearstick. The noises seem to trail off towards redline. As it will be wearing a turbo in a few weeks I want to pinpoint this (possible) problem so that I don't break anything but don't know what could be causing this. Has anyone experienced this before in a 505/504?

  4. #4
    Fellow Frogger! 505 to the max's Avatar
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    Default 505

    Graham, Stuey,
    thanks for the replies. The vibrations seem to be stronger in second, third, and fourth, fifth I don't really know as that would put me in 'automatic suspension of license' territory. It also has a slight shudder or 'grab' on deceleration which may be related. When I first got it on the road (after transplanting the ZDJL motor) it suffered similar symptoms particularly on deceleration but all that was needed was to tighten the torque tube where it meets the g/box, however it isn't loose and the symptoms are the same. Is it possible that when the torque tube worked itself loose that it may have damaged the tailshaft?

  5. #5
    Budding Architect ???? pugrambo's Avatar
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    have you checked the diff mounts, tube to diff bolts, wheel balance

    make sure everything is tight and the wheels are balanced and the engine mounts are in good condition

    i have known people to spend a lot of money on getting vibrations out of a car to only find in the end that it was only a rear wheel out of balance so my advice is to thouroughly recheck everything from front to rear
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