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axle/driveshaft vibration question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by 1989blazer, Jan 23, 2004.

  1. 1989blazer

    1989blazer Registered Member

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    Hey all, just had my axle ratios changed to 4.10's. I've got a lot of vibration coming from the truck's rear end starting at about 45-50 MPH. The mechanic claims its normal because the driveshaft is spinning faster and because of the extra angle from the lift (2.5" lift whoo-hoo). I'm thinking the u-joint's not been put back right. Anyone else had this problem?
     
  2. 1989blazer

    1989blazer Registered Member

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    Anyone done this chnage and NOT had this problem?
     
  3. BranndonC

    BranndonC 3/4 ton status

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    its either the angle or u-joint i agree, but dont know how to tell which one. Did you drop the transfer case or install shims with the list?
     
  4. bablazer73

    bablazer73 1/2 ton status

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    I have never seen a vibration from a driveshaft BECAUSE the gears were changed. I would Ck the ujoint and make sure its in right. and make sure the yoke was instaled right. 2.5 lift isn't alot. I have 2.5 in my 76, no probs, had 2.5 in my wifes 87, no prob vibes there, and had several years with 4" and no vibes till 6".
     
  5. Stickseler

    Stickseler 3/4 ton status

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    Did you do all springs or blocks?? My lift is 2.5" all spring w/a zero rate in back to level it out. I measured the front before and after and it went up 4.5" so I'm sure the back went more. Had somthing to do with 13 year old springs sagging alot. Any way I've got a litttle vibe so I'm going to replace the zero rates with tapered ones.

    The one thing I need to find out is if its normal for the rear u-bolts to lean forward on the top which pushes my pinion down. Its not much but I thought they were straight up and down before the lift /forums/images/graemlins/confused.gif but everythings tight.
     
  6. 1989blazer

    1989blazer Registered Member

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    So I was able to reduce the vibration a lot by re-installing the driveshaft to the yoke turned 180 degrees. I also think that my crappy Kragen u-joint is part of the problem: there's about 3/32 inch side to side slop in the yoke when the bolts are loose. Also, 1 of the 4 cinch strap bolts freezes the side to side play when torqued. I think I'm going to try replacing with a better quality u-joint next to get rid of the rest of the vibration. Anybody know anything about Napa u-joints? are Chevy u-joints better?
     
  7. MA87K5

    MA87K5 1/2 ton status

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    napa u-joints are $$$, call around for a better price and warranty. I had a napa u-joint w/lifetime warranty and it went bad 6 months later and they gave me a run around about the warranty. At least autozone and advance auto never gave me a run around. I have brute force u-joints at every joint. My drive shaft joints are binding due to the lift, need a longer one. It has been like that for about 15 months. I checked the joints for wear and they are as tight as when I put them in. So far so good.
     
  8. bablazer73

    bablazer73 1/2 ton status

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    NAPA ujoints are made by precision. ok, but not the best. I also like the "brute strength" joints by borg warner. My auto zone has them. only a 1.00 more than the napa joints. The one thing that is criticle to ujoint life, it cap preload. so many people crank the u-bolts down and eggshape the caps, causing the joint to prematurely fail. Also, the strap type retainers stretch and loose tension, especially if a joint has come apart in the strap! For a couple bucks more, you can get new straps. My autozone has them.
     
  9. 1989blazer

    1989blazer Registered Member

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    So, I replaced my u-joint with a Spicer. $16. I also was careful to torque the strap bolts to 15 ft-lbs. No slop, no binding, no vibration. The joint I replaced had GMB and Japan cast into the cross, FWIW. Note to self: pay attention to details and don't buy crap.
     
  10. bablazer73

    bablazer73 1/2 ton status

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    yup!! lesson learned. you get what you pay for. Glad it worked out. Vibrations suck!
     
  11. az-k5

    az-k5 1/2 ton status

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    GMB is checker/shucks/kragen afaik. You are right, it is crap.
     
  12. rick88blaze

    rick88blaze 1/2 ton status

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    When I did my 2 1/2" lift, I ended up getting a CV style rear driveshaft. My slip yoke and weld yoke on my driveshaft were hitting each other. But just so you know, none of my mods have turned out to be simple on my truck. /forums/images/graemlins/thumb.gif

    Rick
     
  13. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Autozone carries Neapco u joints.
     
  14. 88jimmy4x4

    88jimmy4x4 1/2 ton status

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    [ QUOTE ]

    The one thing I need to find out is if its normal for the rear u-bolts to lean forward on the top which pushes my pinion down. Its not much but I thought they were straight up and down before the lift /forums/images/graemlins/confused.gif but everythings tight.

    [/ QUOTE ]

    Thats an indication that you need shimming for driveline angles. When your pinion and driveshaft is aligned the bolts will be straight up.
     
  15. 88jimmy4x4

    88jimmy4x4 1/2 ton status

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    Hey 1989blazer....what size tires do you have? hows the new 4.10's with them?
    I need to change ratios myself. I am going to 35's and cant decide between 4.10's and 4.56's.
     
  16. 1989blazer

    1989blazer Registered Member

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    I've got 33's. The 4.10's are great match, especially on the freeway. I can definitely feel the greater rotating mass of tires though. Given that, I'd recommend 4.56's with 35's. Especially if you drive mountains at all or tow.
     

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