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Clutch vibration??

Discussion in 'The Garage' started by Mule man, Aug 23, 2005.

  1. Mule man

    Mule man Registered Member

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    I have most of the vibration out of my truck--finally. It's a '79 k20 with the 465/205 combination. There is a feeling in the steering wheel of a slight high frequency road vibration at all speeds. If I press on the clutch just enough to take the slack out of the pedal (maybe 2 inches) the vibration stops completely in the steering wheel and is tranmitted into my foot. Then I have a smooth ride. I have a new clutch/pressure plate/throw out bearing. Any ideas will be appreciated.
     
  2. Kiwi John

    Kiwi John 1/2 ton status

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    Have you checked the engine mounts, trans mounts?
     
  3. Mule man

    Mule man Registered Member

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    Thanks for the quick reply. I've already installed new motor and tranny mounys.
     
  4. Kiwi John

    Kiwi John 1/2 ton status

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    Are the drive shaft UJ's all lined up correctly?
    Drive shafts need balancing?
    Wheels balanced?
     
  5. Mule man

    Mule man Registered Member

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    Been there--done that. New one piece drive shaft (balanced) with new U joints. It feels like a vibration in the clutch fork. I just don't understand why it is being transmitted into my steering wheel?
     
  6. Kiwi John

    Kiwi John 1/2 ton status

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    steering wheel would imply a front axle vibe?
    wot about swapping the wheels front to back ?
    Could the flywheel/clutch be out of balance? :confused:

    Anyone else???
     
  7. randy88k5

    randy88k5 1/2 ton status

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    Have you replaced the engine recently? I heard something from a friend of mine, never thought of it before but makes sense. The older engines were externally balanced (harmonic balancer and flywheel/flexplate counterweights), and new target motors are internally balanced. You are supposed to run the balancer, but no weights on the other side. He took an air chisel to the weights on the flexplate, and took away all the vibrations :waytogo:

    Good luck...
     
  8. Mule man

    Mule man Registered Member

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    73k5blazer and diesel4me. Your responses to other clutch problems seem to be very knowledgeable. Do you have any advice on this one? Thanks
     
  9. diesel4me

    diesel4me 1 ton status Premium Member

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    out of balance??

    Factory clutches are spun balanced as an assembly much like tires are..they mark the pressure plate with an "X" and the flywheel,so it can be reassembled in its original position..but the first time the clutch gets replced,and the flywheel is turned,all the marks are now gone,and since the flywheel was cut,its no longer "balanced"..how critical this balance is has been debated --but evidently its not THAT critical,or everyone who had a clutch replaced would be complaining..but I imagine it will throw things off somewhat..

    Many things can cause vibration--as mentioned already,the wrong flywhhel for the application will certainly make things shake!--using an externally balanced flywheel in a motor thats internally balanced is bound to make a shaker out of it!

    Misalignment between the tranny and bell housing is a possibility--any grit or dirt between the engine and bellhousing can throw things off enough to be a problem!--tranny mounts tourqued down excessively put a strain on the trannny and the input shaft..Your problem sounds like something is wobbling off center slightly,and its being transmitted to the clutch pedal and linkage,which amplify the vibrations....it could be a pressure plate balance problem,a warped disc,or the springs in the pressure plate or disc are loose or broken..

    If its new,it could be cheap quality parts maybe??-and did you put in a new pilot bushing in the crank??--another possibility is it could be something inside theTRANNY vibrating internally,an out of balance shaft,or perhaps a worn input shaft main bearing---they sound like a scoring noise with the tranny in neutral and the clutch engaged--goes away when you put it in gear with the clutch depressed..-

    Another often overlooked source of vibation is the engine itself!---worn thust bearing surfaces can allow excessive end play in the crankshaft--a fairly common occurance on manual tranny equipped vehicles--any time you hold the clutch pedal down,the throwout bearing is pushing against the pressure plate,which pushes on the crankshaft-literally trying to "push" it out the front of the engine!..

    All that load is concentrated on the "flange" made into the rear main bearing!..any excessive play there can cause vibration,or even a knock--and stepping on the clutch will hold pressure against the thrust bearing,and the vibration or knock goes away.. I had an old 6 cylinder mustang that had SO much end play in the crank,it would STALL when you depressed the clutch! :eek1: :doah:

    You can grab the flywheel or harmonic balancer and pull in and out to check for excessive end lay--should only move a few thousanths of an inch--no more!..and take a long look at the harmonic balancer too!--it might be the whole problem!--if its oil soaked or looks like it "slipped",and your timing marks no longer "jive",chances are its junk!..

    -I'd use only a LUK or Centerforce diaphram style pressure plate--had too many failures and too high a pedal effort with the "3 finger" Borg and Beck style clutches...

    Hope all that didn't depress you TOO much!--hope its something simple,and it could very well be something I missed..I chased a vibration on one truck for months--then one day the fan blade lost a blade!--after I put another fan clutch and fan on it,it was smooth as silk! --I changed motor mounts,and spent a lot of time and money trying to make it right! :doah: :crazy:
     
  10. GMCLegacy

    GMCLegacy 1/2 ton status

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    check the transmission to bellhousing bolts. make sure they are not loose or stripped.
     

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