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Thread: Rotating Clunk from under the car, only in first gear.

  1. #1
    Join Date
    Sep 2016
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    Los Gatos, CA
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    02 BMW 540i/6, 03 530iA

    Rotating Clunk from under the car, only in first gear.

    Hi again, I've got a 2002 540i/6 with an M5 3.15 LSD and I recently started encountering an issue after recently doing a few hard launches. As of the past few days, whenever I take off from a stop in First gear, under any acceleration, I get a few clunks that can be felt on the center arm rest. It feels sort of like someone is smacking the underside of the car with a Rubber Mallet, the size of a sledge hammer. It makes a noticeable noise, and gets louder under harder acceleration. I know for a fact that it's not the rear diff mounts, as a new LSD was installed a little over a year and 15k miles ago. Any suggestions what it may be? I'm going to be doing Trans and motor mounts very soon, as well as redoing the shifter linkage in my car with the Kit from ECS tuning, and definitely flushing out the fluid. I'd like to make it one trip under my car and buy everything at once, as it's very cold outside and I'm a little girl when it comes to the cold. This issue doesn't exist in any other gear, and the entire car doesn't shake at random speeds. Just a clunk and noise at 1200-2200 RPM in first gear from a stop.
    Last edited by nasco; 01-02-2017 at 04:26 PM.

  2. #2
    Join Date
    Feb 2014
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    Caboolture, Q, Australia
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    E39 535i
    Guibo?

    Absinthe makes the tart grow fonder.

  3. #3
    Join Date
    May 2015
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    Atlanta, GA
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    3,608
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    540i6 S2M5 M2C 135 S52ti
    This ^... Your drive shaft is broken and needs repair

  4. #4
    Join Date
    Oct 2011
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    Raleigh, NC
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    SR-71 Blackbird
    It's most likely your CSB (Center Support Bearing). Depending how you get off the line you can hear it rubbing/hitting the transmission tunnel constantly before it goes away. It's most noticeable in first and also in second gear. If you are also noticing this rubbing/hitting action whilst making a turn then it's definitely your CSB.

    Also, you're in the wrong forum to ask. Any E39 related issues are dealt in the E39 forum but not in the hangout section.



  5. #5
    Join Date
    Sep 2016
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    02 BMW 540i/6, 03 530iA
    As of recent when ever I make a really, and I mean really sharp right turn, throughout the turn I can hear a little bit of a rubbing noise, could this be it?
    P.S. Thank You for informing of my mistake about my post location.

    - - - Updated - - -

    Center Flex Disc, the rubber mount that connects the Transmission output shaft to the driveshaft.

  6. #6
    Join Date
    Oct 2011
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    SR-71 Blackbird
    Yep, same here, I'm currently dealing with a bad CSB.



  7. #7
    Join Date
    Sep 2016
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    Los Gatos, CA
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    02 BMW 540i/6, 03 530iA
    I'll try and post a video some time today to confirm the noise I'm talking about. I'm seeing people post these videos about CSB's and it's not making the same sound I'm hearing.

  8. #8
    Join Date
    Dec 2013
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    EXOTICS
    Inspect the guibo(Center Flex Disc) in addition to the CSB.

  9. #9
    Join Date
    Sep 2016
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    Los Gatos, CA
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    02 BMW 540i/6, 03 530iA
    It's in pretty much the same location correct? Do I need to drop the driveshaft in order to inspect the CSB?
    Update: When under the car, rotating the driveshaft led to a clicking noise ar the rear, a little before the differential, probably from the other flex disc at the end. guibo*** looked brand new, had absolutely zero clicking at the other end. I also noticed about an inch or so of unsprung clutch pedal travel at the very very bottom of the throw.
    Last edited by nasco; 01-02-2017 at 11:28 PM.

  10. #10
    Join Date
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    EXOTICS
    https://www.realoem.com/bmw/enUS/sho...diagId=26_0188

    I believe you have to drop the exhaust to access the center support bearing.

  11. #11
    Join Date
    Oct 2011
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    SR-71 Blackbird
    Yes, you have to drop the exhaust and the exhaust shields to get to the CSB. You will also have to drop the driveshaft then split the two main halves to extract the CSB out with a gear puller. There's a 18 or a 19mm bolt between the u-joint. Using only a wrench break it loose and remove it. Before separating the make sure to put some alignment marks so that they go back together in the same manner as before.



  12. #12
    Join Date
    Sep 2016
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    Los Gatos, CA
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    02 BMW 540i/6, 03 530iA
    Question, how would I go about putting the CSB back on? I haven't seen a concrete way of people doing this.

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