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Knocking noise Dino 246 GT

Discussion in '206/246' started by Ferdinand Mayr, Jul 3, 2020.

  1. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
    Hi everyone,

    I have noticed a knocking or thumping noise coming from the rear of my 246 GT.

    The noise only appears when the car is in a gear and is decelerating. No noise can be heard when in neutral.

    It also only starts to knock when the engine is warm.

    The faster I go, the higher the frequency of the noise.

    Any ideas?
     
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  3. TheMayor

    TheMayor Eight Time F1 World Champ
    Rossa Subscribed

    Feb 11, 2008
    81,424
    Vegas baby
    I know this is going to sound really simple but start with the simple things first.

    That would be -- the tires. Then the rims and wheel nuts. Then the suspension bushings. Then the shocks. Then I would check the wheel bearings. Then work your way up to the transaxle. Don't always assume the worst first. It may be something simple.
     
  4. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
    Thanks, but as I said the noise only appears when the car is in a gear.
    Once I press the clutch it‘s gone.

    So wheels, tires, suspension are definitely not the problem.
     
  5. pshoejberg

    pshoejberg Formula 3
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    Dec 22, 2007
    1,402
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    Peter H
    1. Driveshaft issues, CV joints worn: Check rubber boots for damage. 2. Transfer gear issues: Suspend back wheels, set car in gear and listening for indications of worn transfer gears.

    Best regards Peter
     
  6. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
    Thanks for your help Peter!

    Do you think it‘s an issue I should immediately take care of or will it be fine if I wait until the season is over in October?

    Best regards,
    Ferdinand
     
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  8. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
    Heres a video of the CV joint. When I move the left one there is a knocking noise. The right one does not make a noise. I think this could be it!
     
  9. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
  10. TonyL

    TonyL F1 Rookie
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    Sep 27, 2007
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    Tony
    sounds like something has definately broken inside the CV joint, possibly the circlip on the half shaft, dont drive it until its fixed is my advice.
     
  11. daviekj

    daviekj Formula Junior
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    May 9, 2008
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  13. pshoejberg

    pshoejberg Formula 3
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    Dec 22, 2007
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    Peter H
    It sounds like you have a very dry / worn bearing in one side. I would not be overly concerned by using the car for the rest of the season since these bearings are a very tough design. On the other hand it doesn't take long to remove the shafts and install new bearings. I would consider to change out all 4 bearings or at least the two outside bearings witch are the ones that takes the most beating. FYI, Porsche 911 from 198x used exactly the same type bearing joint and can be bought for less the Ferrari factor.

    Best, Peter
     
  14. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
    Thanks to everyone for your help!!

    I just made a quick „inspection drive“. I was able to narrow the noise down even more:
    The knocking sound is only heard when I decelerate with a gear in.

    It can not be heard when I accelerate. Could it be that the engine is just misfiring during deceleration?
     
  15. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
  16. synchro

    synchro F1 Veteran

    Feb 14, 2005
    9,211
    CHNDLR
    Full Name:
    Scott
    Your profile doesn't say but are you in the UK perhaps?

    Item Name Item Price Quantity Item Total
    --------- ---------- -------- ----------
    901-332-293-12-M60 $5.25 4 $21.00
    CV Boot, 911/912 (1969-mid 75), 911 Turbo (1975-84)

    ----------------------------------------------------------------------
    930-332-034-00-M60 $92.25 4 $369.00
    CV Joint, 911 Turbo (1977-84), Brand: GKN Loebro

    These are what I bought, but it appears they have dropped in price 20% ?
    https://www.pelicanparts.com/More_Info/93033203400.htm?pn=930-332-034-00-M60

    PS - pack each one with at least 4oz of grease
     
  17. Ferdinand Mayr

    Jun 4, 2018
    14
    Full Name:
    Ferdinand Mayr-Melnhof
    Thanks a lot for your message! I already bought it.
     

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