S2000 Under The Hood S2000 Technical and Mechanical discussions.

Thud before I engage first gear...

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Old Apr 18, 2007 | 12:40 PM
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Default Thud before I engage first gear...

sometimes when i'm sitting in neutral and i go to press down the clutch...right before 1st gear engages I hear a THUD coming from under the car....nothing too loud but definetly noticeable..is this normal?
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Old Apr 18, 2007 | 12:53 PM
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Yes. I wouldn't worry about it. If it bothers you try waiting a couple of seconds after you press the clutch pedal before putting the shifter in first or shift 4th to 1st.
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Old Apr 18, 2007 | 12:56 PM
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Mine does that too, I thought the driveshaft was moving forward and back, but I dont know much.

edit:called it a drive axle when it is a driveshaft
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Old Apr 18, 2007 | 01:13 PM
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ah ok
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Old Apr 18, 2007 | 01:23 PM
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But before this topic is blown off, any input on what is thumping would be much appreciated.
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Old Apr 18, 2007 | 01:31 PM
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Quick and dirty explanation:

With the clutch out engine running the main shaft on the transmission is spinning. The prop shaft is not. When you depress the clutch pedal the tranny shaft starts to slow and will eventually stop. If you put the car into gear before the tranny stops you reengage the rest of the driveline which causes the tranny to stop abruptly and the prop shaft to try to turn just a bit.
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Old Apr 18, 2007 | 02:22 PM
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Originally Posted by raymo19,Apr 18 2007, 01:31 PM
Quick and dirty explanation:

With the clutch out engine running the main shaft on the transmission is spinning. The prop shaft is not. When you depress the clutch pedal the tranny shaft starts to slow and will eventually stop. If you put the car into gear before the tranny stops you reengage the rest of the driveline which causes the tranny to stop abruptly and the prop shaft to try to turn just a bit.
Thanks for the explanation. I take it that the noise cannot be stopped without slowing the shift process?
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Old Apr 18, 2007 | 02:54 PM
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Originally Posted by dnelson1627,Apr 18 2007, 06:22 PM
Thanks for the explanation. I take it that the noise cannot be stopped without slowing the shift process?
Short of turning off the switch it's hard to rev match 0 RPM.

If you first shift to a higher gear (like 4th) first you can minimize the effect but I don't know of any way to eliminate it short of counting "one one thosand, two one thousand" and then shifting to first.

But that's a bit unpractical when sitting at a redlight huh? I suppose you could stay clutch in from the start but personally I'm not comfortable with that option.
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Old Apr 18, 2007 | 03:09 PM
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Hmmm guess I just have to deal with it. Thanks Alot!!!
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Old Apr 22, 2007 | 11:37 AM
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I just clutch in when the opposite light goes yellow, and engage first gear during that second when both lights are red. Then again the windshield frame cuts right across where most stoplights are hung, so I often look at both lights out the side window, ha.
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