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high speed whining noise

Discussion in '80-Series Tech' started by Doug_Hanney, May 28, 2003.

  1. Doug_Hanney

    Doug_Hanney

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    My 1994 LC has a strange noise at highway speed only when my foot is on the accellerator. The noise sounds more like a faint hum, and stops once the vehicle is coasting. My first thought was dry u-joints, but greasing the zirks did not cure the noise. It's a recent purchase and I haven't had a chance to change the transfer/diffs to fresh fluid and I'm unsure of the fluid last change. Any thoughts?
     
  2. CruisinGA

    CruisinGA

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    mmmmmm worn differentials.
    My 40 made mucho noise even at just 40 mph, mechanic tightening things up in there, I changed the oil, it makes a lot less noise now, still got the slop. I guess this is not as easy to tell in an auto trannyed car, but if there is kind of a hesitation (not engine hesitation) but like the instant you press the gas the car doesn't change speed but hits hard just a moment later the splines on your pinion may be worn, at least thats what mine is. Often with an audible knock, also happens when you let off the gas.
    This is my opinion, based on your transfer not being the culprit. Check the transer and diff oil levels. Maybe the 80 guys got some more guesses. &nbsp:Do you know if your TLC was used to tow heavy loads? At first I would think it would be odd for a differential thats not so old to be flat out wearing out, but I guess this all depends on mileage and degree of use/abuse.
    Open the windows and see if you can tell where the noise is coming from.
     
  3. BMT

    BMT

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    Doug...does it do it when the rig is cold or just when it warms up? Are you sure it is drivetrain? I have a p/s pump that whines when it gets warm and at highway speeds but seems to get quiet when coasting. Just a thought.
     
  4. shocker

    shocker

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    One thing that anyone who will diagnose your problem via the internet will need is more information (the 3 M's) regarding your Cruiser; i.e. mileage, modifications, & maintenance.

    Also, if you can be more specific about the problem itself.  Is it a resonant humming sound?  Does it come and go at a certain frequency?  Or is it a constant sound that happens the entire time you are pressing on the gas pedal?  Humming under acceleration is normally an indicator of U-Joints, and if they have gone bad, greasing them may not take care of the problem.  On the other hand, I had a resonant hum at highway speeds that was caused by an out-of-balance tire.

    The next time you hear it, put your hand on the transfer case lever (a pretty direct connection between the interior and the driveline) and see if you can feel a vibration that is in time with the noise.
     
  5. Desertmaster

    Desertmaster

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    Doug,

    It could be your fuel pump, and in other cases a ball beering calling for help.......more info from you will help.

    Someone from the old SOR forum had a similar problem and it was his fuel pump after all.

    Just my 2 cents.

    Thanks

    Al
     
  6. Doug_Hanney

    Doug_Hanney

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    Thanks for the idea's. I have a 4 hour road trip planned this weekend and I'll try to "hone in" on the noise. Strange the hum only occurs while my foot is on the accellerator? 3 M's = 122,000 Miles, no Modifications, and from what the previous owner indicated, good Maintenance. Other details...1994, diff locks, white, grey leather.
     
  7. landtoy80

    landtoy80

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    Does it do it with the cruise controll on?
    What about with cruise on and foot on acc.?
    kurt
     
  8. semlin

    semlin rocker

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    I get kind of a mild whirring noise under hwy acceleration too. Sounds a bit like a very quiet city bus. Just thought it was normal. Mine sounds like it comes from the drivetrain, and I actually thought it was just proof that the A442 came out of a bus. BTW, anyone know what that bus looked like?
     
  9. medtro

    medtro

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    I have heard this is the noise from the cat. Replacing it should get rid of the noise, assuming other components mentioned by other listers are in good shape.
     
  10. scottm

    scottm

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    Mine is noticeably louder with the rear hatch open, I'm pretty sure it's an exhaust whistle. I suspect a cat, but doubt a high frequency like that could be heard after travelling through all that plumbing and mufflers. Some knowledgeable people have mentioned it could be an edge on the inside of the tailpipe or the opening itself. I haven't really looked at that, I guess I could compare the tailpipe on my wife's 80.