Overdrive kicks in below 45mph

Discussion in 'Engine & Performance' started by ChesterRam, Jan 16, 2019.

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  1. ChesterRam

    ChesterRam Junior Member

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    My 2008 Ram 1500 OD kicks in at speeds lower than 45. Low rumbling, acts like a standard transmission when in too high of a gear. It stops when I turn overdrive off. The OD tends to kick in and out when driving on relatively flat roads 55+.

    Any thoughts on this? It was suggested that the throttle position sensor could be the cause.
     
  2. HemiLonestar

    HemiLonestar Senior Member Military

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    5th gear (which is second OD) + TC lockup + MDS = rumble. Does the exhaust note change a bit when this happens? The factory programming for the transmissions on these things is terrible, plus it's set up for max fuel economy so the trans will get into 5th as quickly as it can.
     
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  3. ChesterRam

    ChesterRam Junior Member

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    The exhaust has a deeper sound when it goes to the higher gear.

    Any thoughts on reprogramming? Is this a dealer function or transmission shop?
     
  4. HemiLonestar

    HemiLonestar Senior Member Military

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    Try giving it just a little bit of extra gas next time, not enough to take it out of gear, but if MDS has kicked in the exhaust note will change slightly and it should stop the rumble.
    Reprogramming how lol? Can't program the factory calibration out unless you get an aftermarket handheld tuner capable of it or a shop that can do it, otherwise you're stuck with the factory trans program lol. A Superchips tuner can disable your MDS and tune your trans, but that's all on you.
     
  5. ChesterRam

    ChesterRam Junior Member

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    At the risk of sounding stupid,what is MDS?
     
  6. Karlsweg

    Karlsweg Senior Member

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    Multiple Displacement System.Short version is it turns your 8 cylinder into a 4 cylinder. Hence why the exhaust note rumbles.
     
  7. ChesterRam

    ChesterRam Junior Member

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    Ok so it’s likely not the trans acting up, it’s the mds kicking in and out
     
  8. HemiLonestar

    HemiLonestar Senior Member Military

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    The rumble would be from only half your engine running while the TC is locked up and lower speed/RPM. Turning OD off also turns MDS off until you turn OD back on.
     
  9. ChesterRam

    ChesterRam Junior Member

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    Thanks All!
    You learn something new every day!
     

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