Bad vibration

Discussion in 'Troubleshooting & Diagnosis' started by Fbomb, Jun 10, 2017.

  1. Fbomb

    Fbomb New Member

    Jan 1, 2013
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    Hi everyone, I am getting a bad vibration around 4000rpm every gear no matter what speed. Over the last two winters I had the engine and transmission and rear differential out of the car. The trans(st10) has been rebuilt and so has the rear diff. The engine is balanced and the rebuild is about five years old.
    here is what I've checked so far: replaced distributor with good spare(no change)
    re-set valve lash(no change)
    removed drive shaft and checked ( checked ok)
    I noticed trans mount bolts were loose, tightened them and vibration is now WORSE!
    Any thoughts?
  2. Fbomb

    Fbomb New Member

    Jan 1, 2013
    So, Ive tried eliminating a couple more items. no success. I took the car for a couple long drives, the motor runs real smooth until just under 4000 rpm and the vibration just turns on. Also while the motor is hot its making lifter noise or tick. Could a bad lifter or cam cause these symptoms?
  3. 1970_Z28_503

    1970_Z28_503 Member

    Apr 12, 2017
    I'm chasing a similar vibration.

    Does your happen sitting still with the clutch in, what about clutch out car in neutral? How are the Motor mounts?
  4. Chevy70

    Chevy70 Veteran Member

    Mar 3, 2014
    I had a similar issue... it turned out there was a problem with my flexplate and harmonic balancer. (Auto)
  5. cadillac_al

    cadillac_al Veteran Member

    Apr 22, 2015
    So, if you are rolling down the road at 3500 rpm there is no vibration. What happens if you push the clutch in (rolling at 3500) and rev to 4000+? I guess I'm trying to determine if it's in the engine/clutch or trans/driveshaft. I guess if it does it in every gear at 4000 it must be the engine/clutch.
  6. BonzoHansen

    BonzoHansen Administrator Lifetime Gold Member

    i was fighting a number of vibrations with a new motor. I had one from 3000 rpm+ and it ended up being a junk new MSD billet hei. Pickup coil was bad. This was after a random misfire issue that ended up being the coil.
  7. Zspoiler

    Zspoiler Veteran Member

    Can you "feel"what area of the car it might be, Or have someone follow you and watch your car.Check the driveshaft as well.

    Attached Files:

  8. Fbomb

    Fbomb New Member

    Jan 1, 2013
    Ran the car in the garage at 4000rpm, vibration was the same with clutch in and out. I can feel it in the seat and floor of the car. After doing some more internet reading I remembered I have the centerforce clutch with that weighted ring on the pressure plate. I'm going to pull trans and see if that ring is stuck out of position.
  9. Cardinal

    Cardinal Veteran Member Lifetime Gold Member

    Jun 22, 2003
    Endicott, NY
    Well, you've divided the problem in half by finding the the vibration still happens with the car in neutral.

    Questions: was the flywheel and clutch plate balanced with the motor? What is your motor = a stroker with an externally balanced system or an internally balanced system = do you have the correct harmonic balancer and flywheel for the type of system you have?
  10. Zspoiler

    Zspoiler Veteran Member

    I have seen people do that.Some 383 Stroker engines are externally balanced and some are not. It depends on the builder. I would not run the engine again until you check and see what it is. Otherwise it could get very very expensive .by "blowing it up" the engine.

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