So what does it mean if the back wheels turn while the transmission is in neutral?

Discussion in '2005+ Mustang GT 4.6L Tech' started by ghunt81, Sep 9, 2019.

  1. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    This is a new one.

    Over the weekend I was working on my exhaust so I had the car up on jack stands. Last night I had it all wrapped up so I started the car to let it run and check for leaks. Pulled the shifter into neutral, clutch in, started the car, clutch out. Got out of the car and I notice the back wheels are turning, slowly. I could stop them with my foot but once I let my foot off they would slowwwwwly start spinning again. After it ran for a few minutes I stopped them with my foot again and they didn't spin anymore.

    How is it even possible for them to turn when the transmission is completely out of gear? What would cause this?
     
  2. MrAwesome987

    MrAwesome987 forum member

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    Pretty sure this is normal.
     
  3. Racer47

    Racer47 Doesn't have much to say S197 Team Member

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    transmission drag will spin the driveshaft, no big deal, its fine
     
  4. tjm73

    tjm73 of Omicron Persei 8 S197 Team Member

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    I feel like there was another thread about this EXACT thing a couple years ago.
     
  5. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    I thought when the transmission was in neutral the output shaft was not engaged. Well, I guess I thought wrong all these years.
     
  6. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    The clutch failing to completely release would be the reason. Do you have a hydraulic fluid leak?
     
  7. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    Clutch doesn't really factor in if the transmission's in neutral and the clutch is out.
     
  8. WJBertrand

    WJBertrand forum member

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    The output shaft is not mechanically engaged, but both shafts are immersed in the transmission lubricant. The output shaft is turning simply because the viscosity of the lubricant is transferring some small amount of torque from the spinning input shaft. This will be particularly evident when the transmission is cold, it would probably not occur if the transmission lube was warm.
     
  9. Racer47

    Racer47 Doesn't have much to say S197 Team Member

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    The output shaft is not engaged. If it was, you would not be able to stop the tire spinning.

    ok lets step through this...
    Car on jacks, engine running, trans in neutral, clutch engaged
    The input shaft on the trans is spinning with the clutch and engine
    The countershaft in the transmission is spinning, its geared directly to the input shaft
    The counter shaft is spinning all the drive gears on the mainshaft/output shaft.
    None of the mainshaft drive gears are locked to the output shaft but with cold temps or thick trans oil there is enough friction drag to slowly turn it anyway.

    edit, wjbertrand beat me by a couple mins, i need to type faster :)
     
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  10. ghunt81

    ghunt81 New parts on old junk! S197 Team Member

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    Makes sense. I just don't think I've ever seen it do that before.
     
  11. Dino Dino Bambino

    Dino Dino Bambino I have a red car

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    Interesting explanation from an engineering perspective and it makes a lot of sense.
     
  12. WJBertrand

    WJBertrand forum member

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    Pretty commonly seen with motorcycles on their center stands that elevate the rear wheel, when started from cold. Cars don’t have center stands so not commonly seen.


    Sent from my iPhone using Tapatalk Pro
     
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  13. 01yellerCobra

    01yellerCobra forum member

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    My old Bug used to do that too.