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1984 K-5 with a vibration

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by RMA, Dec 1, 2002.

  1. RMA

    RMA Newbie

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    I recently found a '84 K-5, 305, NP-208, 700R4, 3.73 posi, 235 X 75 X 15 tires with 42,000 miles from the original owner. Nice piece! The truck is stock except for the 235 tires.

    I searched previous posts for my problem and all posts referred to mofified suspensions. My problem is:

    I have a speed related vibration that starts early 30's, ends about 42, starts again about 55 and remains up to 70. I have changed the u-joints without any change to the vibration. Tires and wheels are in balance. We put the truck in 4 wheel high and pulled the rear drive shaft and the vibration was eliminated. We changed drive shafts and found no change to the vibration. Most all the posts I read indicated the angle of the drive shaft from the transfer case to the rear end was the cause of vibrations when lift kits were installed and I don't know if this could be the cause with a stock suspension. I have my mechanic wanting to pull the rear end apart and I am cautious of the intrusion as well as the cost for the exam.

    Any/all help or advise is welcome.

    RMA
     
  2. mudhog

    mudhog THEGAME Staff Member Super Moderator

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    you will get more replies in the 4x4 forum and not the 2x4 forum ill move it to the second generation 4x4 forum /forums/images/graemlins/smile.gif
    as for your problem it could be a slightly bent drive line or a out of balance drive line
     
  3. KShortell

    KShortell Registered Member

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    You mentioned 2 different speed ranges that the vibration occurred. This keys me in to a specific engine rpm range.

    CHECK THIS (it was the last thing I replaced/fixed/checked) before I solved my nagging vibration-- Remove the dust cover from your transmission bellhousing and look at your flexplate with your engine running. I wouldn't be surprised if it has a sizeable amount of runout...

    Check here for more on my solved problem: http://www.geocities.com/kevinshortell/Tech/flexplat/Flxplate.html

    Good luck! Hope this helps...

    Kevin
    /forums/images/graemlins/burb.gif
     
  4. RMA

    RMA Newbie

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    Thanks for your replies...

    1) My first time on the fourm and leave it to me to place my question in the wrong place. Thanks for moving it to the proper place. RMA

    2) RPM has no effect on the vibration. During the speeds mentioned, I can manually down shift and the vibration does not change. Initally, I considered the flex plate as well as the harmonic balancer but eliminated them when we pulled the rear shaft (in 4-W-H) and lost the vibration. RMA
     
  5. drivelineman

    drivelineman 1/2 ton status

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    balance the driveline - and also make sure your clips are on the free caps on the diff end- every other guy forgets those- Jess
     
  6. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Check your transfer case mount. They are prone to failure in those years.
    Problem could be in the rear end also and be torque related. Does it go away when you coast?
    Do what Jesse (driveline man) say's. He's the drive shaft expert as far as the wheeling world is concerned.
    Those slip yoke cases were prone to vibration when lifted and known for a nice little clunk they give when dropping them into gear. Might try to check the run out on the output shaft on the case and the pinion. It only takes one idiot to put it on a lift wrong and have the driveshaft come down on the cross bar cause stuff to get bent.
     
  7. RMA

    RMA Newbie

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    Thanks DRIVELINEMAN AND GRIM-REAPER...

    I made an appointment for this Wednesday to have the drive shaft balanced and to to check for run-out. We already checked the mounts and found them to be OK. The yoke slips in and out of the transfer case well but occasionally does klunk when torque is removed. RMA
     

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