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Vibration at 40-50 mph with slight grinding noise.

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by BLAZEN70, Apr 2, 2003.

  1. BLAZEN70

    BLAZEN70 Registered Member

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    /forums/images/graemlins/1zhelp.gif Just started a couple of days ago. Vibration and noise barely noticeable at first but getting worse. I can feel it in the floor boards but can't pinpoint where the noise is coming from. Not sure if its trans (sm465) or rearend (12 bolt), or something else. Any help would be greatly appreciated since this is my daily driver. Thanks, Robert /forums/images/graemlins/k5.gif
     
  2. MTBLAZER89

    MTBLAZER89 3/4 ton status GMOTM Winner

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    Have you investigated your U-joints? They often cause a vibration and when they get worse they will make some very bad noises. Cheapest and easiest thing to check first.
    -Brian
     
  3. Chris_T

    Chris_T 1/2 ton status

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    Have you thought about the T-case. I have an unspecified noise that sounds similar, manifested after going from 3.73 to 4.56 .. I can feel it in the transfer case shifter. Not sure if it is a result of higher rpms due to the new gears or a problem that just popped up at the same time. I know mine is not axle-related as it is still there when the rear shaft is not hooked up. New U-joints didn't do anything for me, but it's a cheap place to start and probably worthwhile doing anyway if you haven't changed them lately.
     
  4. IGOR

    IGOR 1/2 ton status Premium Member

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    Check your U-joints first, then rear end
     
  5. '72brett

    '72brett 1/2 ton status

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    Im not sure, but could the drive shaft be out of balance?
     
  6. BLAZEN70

    BLAZEN70 Registered Member

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    Chris, i think it is the t-case. I can feel the vibration in the shifter and when i shift it, the noise changes. All my u-joints look fine. Any suggestions on how to fix? I have one of the rare dana-20s. /forums/images/graemlins/confused.gif If anyone else has had the same problem, please let me know.
     
  7. cleszkie

    cleszkie 1/2 ton status

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    A bad U-joint will cause vibration in the transfer case and shift lever. If the vibration changes when you shift, it may only be due to the change in path the vibration is taking through your t-case. U-joint vibrations can manifest themselves in many ways and places on your truck. I had a vibration that I thought was a bad front spindle bearing that turned out to be a bad U-joint in the rear driveshaft! Good Luck.
     
  8. 70~K5

    70~K5 1/2 ton status

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    Check your yokes too, A loose nut holding the yoke on can feel like a bad U-Joint.
     
  9. Chris_T

    Chris_T 1/2 ton status

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    I'll second what everyone else has said. Just because you can feel it there, doesn't mean it is the T-case. you can try to diagnose it by removing the rear shaft - if it goes away, you have a rear-end or driveshaft problem. The reason I suggested T-case is because of the grinding noise. I'm almost 100% sure this is where mine is coming from because I did the front shaft/rear shaft thing and the noise was constant and was speed and not rpm dependant. I've also had the loose output yoke nut and it does sound very similar. In fact I think my problem now might be due to damage incurred while the output yoke was loose. I would try and exhaust all possibilities before I tore into my T-case or rear end because you'l be mad as hell if you put it all back together after an axle or T-case rebuild and it does the same thing.

    All I can tell you about Dana 20s is that they hurt when you drop them on your toe, sorry.
     
  10. BLAZEN70

    BLAZEN70 Registered Member

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    If it is a u-joint then is there some sign that it does need replacing without taking everything a-part? Everything looks fine. There is no play on the driveshaft, other than twisting it, then it only moves about a 3/4 inch in gear. There is no "clank" when i shift either. Just the constant grind. Yesterday seemed to be worse than today. /forums/images/graemlins/confused.gif I don't think its the driveshaft because the noise is constant at different speeds. Thanks for all the suggestions so far. Im learning alot. I've also checked the yoke and all the bolts and everything is tight.
     
  11. cleszkie

    cleszkie 1/2 ton status

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    Even if your U-joints feel good, I'd check/replace them anyways. The little needle bearings in the trunion cap can begin disintegrating and/or welding together long before there is any real play in the joint. An imperceivable amount of play in a joint makes a big difference at 100s of RPMs.
     
  12. 70~K5

    70~K5 1/2 ton status

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    After you've run a couple of miles slide under the truck and feel the u-joints carefully, don't want you to get burnt, If a U-Joint is going bad it'll be real hot. If only 1 cap is real hot then that end of the cross is going bad. Don't just grap them though use extrem care when doing this. Hold your hand close but not touching first and see if you feel heat radiating from the parts. If they're all cold drive some more and check again. Anything thats not getting proper lube will heat up pretty fast.
     
  13. BLAZEN70

    BLAZEN70 Registered Member

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    Thanks for all the info. I'll do the heat test on saturday. /forums/images/graemlins/thumb.gif
     

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