driveline Vibration....driving me nuts

Discussion in 'Trucks and Trailers' started by mike lane lawn care, Apr 29, 2008.

  1. mike lane lawn care

    mike lane lawn care LawnSite Bronze Member
    Posts: 1,707

    hey guys. got a question i can't figure out. my truck has a very distinct vibration that feels like it's coming from the mid section of the drive line, about half way through the truck. but, it only occurs at 1250-1350 RPM. whenever the engine hits that range, it vibrates, whether accelerating, decelerating, or coasting, if the engine falls into that range, it vibrates. and i can't figure it out.

    Help.....Please!!!!!!
     
  2. jaybird24

    jaybird24 LawnSite Senior Member
    from midwest
    Posts: 623

    Check the u-joints, had this a few times and thats what I always found. Fix it and viola.
     
  3. pclawncare

    pclawncare LawnSite Senior Member
    Posts: 991

    I dont know about this specific truck and if it has one but does it have a carrier bearing? It might be going bad
     
  4. fiveoboy01

    fiveoboy01 LawnSite Silver Member
    Posts: 2,988

    U-joint going bad or a midship bearing if you've got one, looking at both of those vehicles in your sig I doubt they even have a midship bearing.

    A u-joint going out will display all the symptoms you've mentioned. Get under the vehicle and push on the driveshaft at the u-joint, also grab the driveshaft and try to twist it. If the u-joint is loose, you'll see/feel the play.
     
  5. mike lane lawn care

    mike lane lawn care LawnSite Bronze Member
    Posts: 1,707

    k, thanks guys, i'll give it a try. i just replaced the U-joints not 10k ago, but i have been driving in hard conditions and in mud and deep water.
     
  6. mag360

    mag360 LawnSite Silver Member
    Posts: 2,446

    u-joints you will notice at a certain speed---not at a particular rpm.
     
  7. hockeypro1411

    hockeypro1411 LawnSite Senior Member
    Posts: 271

    as i can see u drive a gm truck. same problem on a brand new sierra we just picked up, and the same story on my friends 06 silverado 1500hd. at around 30-35, and 40-45 mph there will be a "rumble". since everyone i know with a gm truck has had this from the get go i assume its normal
     
  8. mike lane lawn care

    mike lane lawn care LawnSite Bronze Member
    Posts: 1,707

    this is different from that, that is at a speed in MPH, the one i'm having is a speed in RPM. and to my knowledge that rumble at 45, is the transmission going into overdrive to lower the RPM to increase fuel economy. but it makes the engine lug.
     
  9. mike lane lawn care

    mike lane lawn care LawnSite Bronze Member
    Posts: 1,707

    In the process of replacing my e-brake assembly, i checked they U joints, and they are worn pretty good. so i'll try that and hope to hell it works. only other thing i can think of would be driveshaft balance.
     
  10. DiyDave

    DiyDave LawnSite Bronze Member
    Posts: 1,695

    How to describe this here? U joints are crosses or look like a plus sign, so picture this... +----X---+. Suppose that the first + is your first joint, the X is the second joint, the second + is the next joint, etc. all joints in a shaft need to be aligned so that when the shaft bends, like when you are hitting a bump etc the drive line is parallel at all of the joints. Sometimes when the joints are assembled after a repair, if you don't note how it was originally assembled, you can mis align the joints on the sliding portions of the shaft. In the example above, the X joint is rotated 45 degrees to the other 2. When dissassembling, take a paint marker, and put a dot of paint at each point to be dissassembled, and putting it back together is loads easier. Also check to see that the sliding areas of the shaft are not dry, they need some lube to slide easily.
     

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