Knocking sound in rear of 328 over bumps.... | FerrariChat
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Knocking sound in rear of 328 over bumps....

Discussion in 'Technical Q&A' started by Manta, May 22, 2007.

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  1. Manta

    Manta Rookie

    May 22, 2007
    7
    #1 Manta, May 22, 2007
    Hi guys

    I have a 328 and didn't know where to turn. There is a moderate knocking sound over washboard bumps in the back. My mechanic can't see anything wrong.

    He thought it was the shocks, so first we replaced the bushings but it made no difference.

    He still thought it was the shocks, so he convinced me to either replace them or have them rebuilt. I sent them out and had them rebuilt. Now it's worse.

    I spoke to the shop that rebuilt them, they are a very highly qualified Koni service center, and they're convinced the problem lies elsewhere and has now only been exposed. Since they do a battery of tests on shocks they rebuild I tend to agree.

    My mechanic is now scratching his head. "It's a simple setup", "there's nothing loose" is all I keep hearing. But something is still wrong.

    Can anyone offer any tips?

    Thank you very much.

    M
     
  2. Jdubbya

    Jdubbya The $10 Trillion Man
    Silver Subscribed

    Dec 28, 2003
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    #2 Jdubbya, May 22, 2007
    Check the rear deck lid. It seems that mine even when adjusted as close as I can get it it still has some play in it. It doesn't seem like this could be the culprit but you may be surprised!
     
  3. f355spider

    f355spider F1 World Champ
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    May 29, 2001
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    #3 f355spider, May 22, 2007
    I had a similar noise on my 78 308GTS. I traced it to the front bank header pipe...as it passed over the frame rail on the right side (passenger) it would occaisionally touch. The solution was to gently bend the heatshield surrounding the pipe, so it would no longer touch the frame rail. That fixed it.
     
  4. spiderseeker

    spiderseeker Formula 3

    Jul 22, 2005
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    Steve
    #4 spiderseeker, May 22, 2007
    Any chance the exhaust is hitting on something ? Or Maybe loose or broken engine mount ?
     
  5. spider348

    spider348 Formula 3

    Nov 3, 2003
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    #5 spider348, May 22, 2007
    Talk to Birdman. He had an annoying clunk in the rear of his 308. Sent the Konis for rebuild, clunk remained. Installed QA-1's with new springs etc. Clunk eliminated.
     
  6. jeremydixon

    jeremydixon Rookie
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    Nov 6, 2003
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    Jeremy Dixon
    #6 jeremydixon, May 22, 2007
    Hi one posibility
    Had the same problem for 3 years on my 328, finaly after much investigation turned out to be the LHS wishbone ( A arm) fouling on the transfer housing casting. A bit of gental use of an angle grinder solved the problem in about 1 hour
    Best of luck.
    Cheers from the UK
    Jeremy
     
  7. Manta

    Manta Rookie

    May 22, 2007
    7
    #7 Manta, May 22, 2007
    That sounds like my case. But what are QA-1's? Where do you get them?

    Great ideas guys, I'm sending them to the mechanic as we speak.

    Thanks.
     
  8. Manta

    Manta Rookie

    May 22, 2007
    7
    #8 Manta, May 22, 2007
    Thanks. I'll get them to check that as well.

    I should have mentioned that at first the right rear was the main complaint, but the left rear wasn't hardly an issue. But once I had the shocks rebuilt the right rear was worse, and the left rear was just as bad, so it really took a turn for the worse. But again, stronger shocks might just be highlighting some other problem.

    So whether now or before, it wasn't a "central" sound, but more located on each side.
     
  9. Manta

    Manta Rookie

    May 22, 2007
    7
    #9 Manta, May 22, 2007
    They say they checked the engine mounts and they are fine. But maybe they should double check there, thanks.
     
  10. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
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    THE Birdman
    #10 Birdman, May 22, 2007
    Hey Manta (Ray?)

    I had serious clunking issues in my rear Konis. Someone here told me it was the Konis and I had them rebuilt (long story, but I don't think the company that rebuilt them did squat to them except put them on a dynometer and make me a pretty graph, and then spray some paint on them). It didn't fix the clunk, so I thought the clunk was from someplace else. I spent more than a year trying to find it (replaced ALL suspension bushings, checked engine mounts, headers, etc.) before I decided that it HAD to be the Konis and I needed to replace them.

    I chose to use QA1 adjustable shocks so I could adjust the ride height of my car.

    If you have a clunk that sounds like it's coming from the suspension and all your bushings are OK, chances are VERY VERY good that your Konis are the source. They suck. If you want to get rid of it, just buy new Konis. DON'T have them rebuilt. (Oops, I see above that you already did....oh well). It won't fix them in my experience.

    Read this thread, and you will be an expert:

    http://www.ferrarichat.com/forum/showthread.php?t=134442

    First read page 10, post 182, then go back and read the whole thing. If you still have questions, let me know!!

    I was never so happy in my life as my first ride with the stupid clunk gone!!

    Birdman
     
  11. Manta

    Manta Rookie

    May 22, 2007
    7
    #11 Manta, May 22, 2007
    Thank you very much.

    I think then it is still the shocks. I don't want to go through all of the customization you did, so I told my mechanic to make a quick check on all of the suggestions offered here so far, and if none check out, then I will order new Koni's tomorrow.

    Thanks all!
     
  12. f355spider

    f355spider F1 World Champ
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    #12 f355spider, May 22, 2007
    Good plan, just get new if needed.
     
  13. drjohngober

    drjohngober Formula 3

    Jul 23, 2006
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    #13 drjohngober, May 22, 2007
    Common problem. Make sure the heat shield broken has not broken free. I ( and two friends ) had same issue and expected shock/bushing problems. Make sure shield mountings have not melted .
     
  14. 4redude

    4redude Formula Junior

    Jan 13, 2005
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    Brian Keegan
    #14 4redude, May 23, 2007
    Check the shock bushings, specifically the I.D. where the bolt goes through. It should be a hair over 12mm, but a recent batch was more like 12.4-12.5mm I.D. A quick visual inspection of the plating color should determine old batch (cad 2/gold) or new batch (clear zinc/silver). This ain't somethin' you'd normally be lookin' fer.
     
  15. Manta

    Manta Rookie

    May 22, 2007
    7
    #15 Manta, May 24, 2007
    That is very interesting, thanks.

    The first thing we tried was new bushings, ordered from TRutlands, so I would think they would be correct,
    but we'll have a look at that as well.
     
  16. Manta

    Manta Rookie

    May 22, 2007
    7
    #16 Manta, Jul 22, 2007
    Well we finally got new shocks in and the knocking sound went away. Thanks everyone for your help. It is hard to believe it was the shocks, harder to believe rebuilt ones were no better, but new (old stock) did the trick for me. What a relief....but what a cost....ouch.

    I still can't see why the old ones would knock. I work them by hand and they seem solid and stiff. Now I'm thinking maybe too stiff? Do you think maybe the shop that rebuilt them made them too stiff, thus exposing a loose joint somewhere else? They really are quite stiff....can hardly move them by hand.

    What do ya think?
     

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