Vibration when stopped at light.

Discussion in '1970 - 1973 Specific' started by john Gialanella, Mar 21, 2020.

  1. john Gialanella

    john Gialanella Veteran Member

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    This has me stumped. My 1970 SS 396 L34 Camaro with TH400 transmission vibrates (it sounds like it is the back passenger side.) when I am stopped at a light. When I drive it their is no vibration. I thought maybe it was the TH 400 mounts, but if that was it, then the car would vibrate when I am driving which is not the case. It seems strange to have vibration when the car is at a standstill. The TH 400 is not turning, the drive shaft and rear axle also are not spinning. It makes no sense to me. Maybe a member might have an idea. When I put the Trans in neutral the vibration stops.
    Thanks John.
     
  2. ULTM8Z

    ULTM8Z Veteran Member

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    Is the car itself vibrating, or something on the car is vibrating?

    What happens if you're stopped, in gear, and then press on the gas a little to raise the idle speed? Does it go away?

    My guess is something is hitting a resonance, excited by the engine rotational frequency and when you're in gear the engine has ability to excite it through the drivetrain.
     
  3. Gary S

    Gary S Administrator Lifetime Gold Member

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    It sounds to me like a small engine miss. When it is in gear, the load is on the engine and you feel the miss. Then when it is in neutral, the load is off the engine and it turns more smoothly.
     
  4. john Gialanella

    john Gialanella Veteran Member

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    Thanks for responding. Next time I take it out for a ride (maybe Sunday) I will step on the gas a little and see what happens. As for small engine miss the Camaro has a lot of power if I step on it. But I guess I will check the spark plugs again. I had new split fire plugs that I installed about a year ago. Anybody have any opinions on these plugs. I do not even know if they still make them. thanks ULTM8Z and Gary.
    John.
     
  5. jbloake

    jbloake Veteran Member

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    Possibly torque converter shudder .
     
  6. BonzoHansen

    BonzoHansen Administrator Lifetime Gold Member

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    Split fires? I thought they went away years ago. Junk if its what im thinking about.

    Put fresh ngk or delco plugs in it.

    I assume a 70 has no egr.
     
  7. xten

    xten Veteran Member

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    I would have someone put it in gear applying the brake. Open the hood in complete darkness and see if you have anything arcing.
     
  8. wnmech

    wnmech Veteran Member

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    Possibly an exhaust pipe or the muffler rubbing against the frame
     
  9. Dave Nelson

    Dave Nelson Veteran Member

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    ^^^^ This would also be my guess.
     
  10. john Gialanella

    john Gialanella Veteran Member

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    Wnmech & Dave.
    That sounds like it could be it, because the vibration sounds like it is coming form the rear passenger side near axle. I will check it out. It might snow tomorrow so I might have to wait. Thanks to all who responded.
    John.
     

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