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vibration...

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by delta9blazer, Aug 30, 2000.

  1. delta9blazer

    delta9blazer 1/2 ton status

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    i recently picked up a vibration in my blaze.
    it starts at about 25mph, fades, then gets rough at 45 and up. almost like my tranny isn't shifting down, and the engine lugs. or driving down a mild washboard road. if i let the throttle off, it mostly goes away. if i put it in neutral and coast, it's very smooth, with no engine miss or anything.
    i'm gonna have a mechanic ride with me today after work, but i'd rather not commit to an appointment if someone can give me a hint to some typical blazer problems.
    thanks!

    <font color=purple>delta9blazer</font color=purple>
     
  2. Check out your U-joints in the back driveshaft. Take a look at them and make sure they are greased (they should have a grease fitting). Then take each yoke in a hand and try to turn them in opposite directions. Try that for both U-joints (on each end of the shaft). If they move independently, then the U-joint is bad. I had about the same symptoms a few weeks ago. If you let off the gas or put it in neutral and the vibration fades and then stops, then it is most likely driveshaft related. Do a quick search in the forum on u-joints or even vibration to find a lotta info. Let me know how it goes. Hope I helped!
     
  3. Peeetah

    Peeetah Registered Member

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    It's interesting to hear so many people with this problem. My Jimmy vibrates from 25 to about 30 mph. I took it to a very good shop and they said it was a because of the 4 inch lift. he said 33s and a 4 inch lift is bound to cause vibration in the truck. He suggesting just living with it.
     
  4. USMuscle

    USMuscle Registered Member

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    I'd be willing to bet that its the transfer case, and/or possibly the U-joints. I haven't personally had this happen to me, but the symptoms would point to this logical conclusion. It's not a wheel balance issue (Unless you have firestone, haha) or else this would happen regardless of gear. Try driving in second gear only, and then first gear only, and seeing if it happens when you go over 25 in 1st. If not, then it's 98% a tranny issue. The only reason I say u-joints as a possibility is because this happens at higher speeds, where irregularities that may have developed in the u-joints would begin to appear. Also, coasting in neutral would slow down the speed at which the driveshaft is spinning, which would lower any vibration related to the speed of the shaft.
    I still say its the tranny.
    -US
     
  5. delta9blazer

    delta9blazer 1/2 ton status

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    thanks for the responses. i'll take a look at the u-joints, and try the non shifting test.
    the truck has 33's with no lift, and it's never had this problem before.
    i already searched this board using vibration, i'll try with drive-line.
    again, thanks for the suggestions.

    by the way, are u-joints easy to change? i'm a fairly competent motorcycle mechanic (OK, i'm not incompetent...), but limited experience with cars and trucks. i have the crappier of the two self help manuals, i don't remember if it's haynes or chilton's.
    <font color=purple>delta9blazer</font color=purple>
     
  6. fr8train

    fr8train 1/2 ton status

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    Just a thought, how agressive is your tire tread. The reasoning behind this is the vibration can be a resonation inside the cab due to tire pattern. Does this happens on flat road at any speed? Also have you replaced the front steering stabilizer? It may be a good time to upgrade. It does however sound like the CV joint bug. Also check if the drive line angle has been altered.
     
  7. Blazer79

    Blazer79 1/2 ton status

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    Also, check that the nuts & bolts that hold the t-case crossmember are tight. If they are loose, they will cause a vibration.

    <font color=blue>//////
    http://blazer79.coloradok5.com
    </font color=blue>[​IMG]
     
  8. delta9blazer

    delta9blazer 1/2 ton status

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    culprit was front u-joint. scary to picture that thing letting go. the yoke was also damaged, truck is in the shop right now. should get it today.

    anyway, thanks for the help.

    <font color=purple>delta9blazer</font color=purple>
     
  9. Panther

    Panther 1/2 ton status

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    Glad to hear you found what it was before it was too late.

    From what I hear, if the joint/yoke breaks, chances are
    the driveshaft will hit the ground, while continuing to go around and then smack up through or against your floor. Therefore ruining your driveshaft and your floorboards. Not a pretty picture.
     

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