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Thread: dynamic stability control .......

  1. #1
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    dynamic stability control .......

    I have a LOT of thump and thunk in my drivetrain upon daily travels. My 03 three wagon has the optional "DSC" system...It is the shadow image of GM's Cadillac "Stabilitrak" automatic transmission-suspension...recoil to instabil road conditions.

    Upon the delivery of BMW 'DSC' is 'drive shaft breaking' an element (computerized) employed before human foot breaking. The transmission is a key player...for DSC.

    Has anyone any input here?

    We have a button to deactivate DSC....and when I deactivate...my car no longer has heavy transmission thunks...and runs smooth with DSC disengaged... comments?...NOTE all BMW cars with DSC start with the ignition switch..all are ON...unless you disable.....with the switch located next to the seat warmers below the Business CD.
    Last edited by Eaglesail; 10-17-2017 at 03:56 PM.

  2. #2
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    Hello - I'm not quite understanding what you're asking here. The DSC has to do with the prevention of skidding - it improves a vehicle's stability by detecting and reducing loss of traction.
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  3. #3
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    Exactly what I thought after trying to read it

  4. #4
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    If the DSC system is falsely triggering (perhaps from wheel sensors that need to be cleaned of metal shavings) the reduction in engine power might be causing a bad flex disk or driveshaft center support bearing to clunk?

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    DSC uses wheel speed sensors, steering angle sensor, yaw sensor, throttle sensor, and a brake pedal sensor to control slippage of each wheel or correct oversteer. This is achieved by the ABS module controlling tire slippage by applying pressure to the slipping wheel's brake caliper individually and reduce throttle input. You could be having some DSC interference with your vehicles operation but the transmission has zero to do with the DSC system.
    Last edited by dhurley34; 11-06-2017 at 11:41 AM.

  6. #6
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    The DSC system can also reduce engine output power, and uses that control in preference to braking when feasible.

    CAN bus was used sparingly in the e46 because it was still expensive back then. The DSC communicates with the engine ECU over CAN bus specifically so that it has reliable, low-latency communication to reduce engine output power.

    A thunk coming from the transmission area is probably the flex disk, which is easy to inspect. A clunk from the middle of the transmission tunnel is the center support bearing, which is hidden. The flex disk can fail on its own. The CSB usually fails because some other failing part puts stress on it. The drive shaft joints should be checked when the CSB is replaced.

    In this case I suspect the flex disk. If it's not replaced soon after it goes bad, then the CSB will fail. If a bad CSB is not replaced quickly, the CSB mounts on the body will be destroyed. Then repairs will be.. expensive.

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    My question is; have you scanned for errors, specifically within the DSC system, with a BMW specific scan tool/software?
    Also, are you running on tires with similar diameters?

  8. #8
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    Quote Originally Posted by MIKYZZ4 View Post
    My question is; have you scanned for errors, specifically within the DSC system, with a BMW specific scan tool/software?
    Also, are you running on tires with similar diameters?
    Diff diameter tires would destroy the transfer case as well.

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