Whining noise from rear axle

Discussion in 'The Garage' started by jkersenbr, Oct 12, 2007.

  1. jkersenbr

    jkersenbr Golden Member

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    I've got a 2000 Dodge Dakota that is making a high-pitched whine from the rear axle. It's the "heavy duty" option 9" rear end WITHOUT limited slip. Has 96K miles on it and the fluid looks pretty clean. (I've only had the truck for the last 12K)

    It starts as a slow whirring sound around 20MPH and increases to a whine at highway speed. The noise changes little with acceleration and deceleration.

    It's made the noise to some extent as long as I had it. I just thought it was gear noise. But lately it's been getting worse.

    I thought maybe I was mistaking tire noise, so put it up on jacks and ran the rear wheels off the ground...still does it.

    What do you think? Are the ring and pinion toast? Or maybe just bearings?

     
  2. SparkyJJO

    SparkyJJO Lifer

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    I'd get the differential checked out. If it is getting worse that is not a good sign.
     
  3. iamwiz82

    iamwiz82 Lifer

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    Does it only occur on acceleration?

    I would guess that it's a bearing by your description. You may as well have all of them replaced if the diff is disassembled.
     
  4. mrblotto

    mrblotto Golden Member

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    U-Joints?
     
  5. jkersenbr

    jkersenbr Golden Member

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    No it does it both accelerating and decelerating. Also coasting, even in neutral.





    The U-Joints are OK. I know what they sound like and this isn't it. They click, ping, and vibrate, they don't whine like a dying TV.


     
  6. Gillbot

    Gillbot Lifer

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    Bearing and/or gears. I've hears U-joints whine also.
     
  7. iamwiz82

    iamwiz82 Lifer

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    Sounds like bearings then. Gears normally only whine on accel or decel, though it is possible to have gears whine continuously. I have never seen that personally.
     
  8. woodie1

    woodie1 Diamond Member

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    "No it does it both accelerating and decelerating. Also coasting, even in neutral. "

    That sure sounds like a bad bearing.
     
  9. mrblotto

    mrblotto Golden Member

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    On a slightly related note (no hijack intended), I had the rear diff changed out of my very first new vehicle: an '88 Dodge Dakota. Anyhow, for some reason I guess the real mechanics were on vacation, because a 'higher gear' rear diff was installed. My speedo would say 50, but I was actually going 60. For a few days I thought I was just going crazy 'cause I would be driving down a hill and think 'man, it feels like i'm flying down the road.....' lol

    /end hijack
     
  10. iamwiz82

    iamwiz82 Lifer

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    Impossible. Dakotas read the speed well before the differential.
     
  11. Gillbot

    Gillbot Lifer

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    It doesn't matter where the speed is read as they are calibrated for a certain number of pulses per revolution. Unless you are taking speed on the rear wheel exactly, changing the gear ratio will alter the speedo unless calibrated for.
     
  12. funboy6942

    funboy6942 Lifer

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    Bad bearing as suggested, or just change the diff fluid for it is low, and has been since you got the truck. The fluid can also leak into your drums so look at the tires on the insides for wetness, sign of diff leak, or brake fluid leak. But if the bearing or low, to noe, or very thin, worn oil will cause the moving sound you speak of.

    Also I am not sure but does that truck us a split drive shaft? If so may want to check the bearing at the split as well.
     
  13. Demon-Xanth

    Demon-Xanth Lifer

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    I don't know for sure about the '88 Dakota. But the '97 and up measure the speed off of the ring gear, so changing the gear ratio does NOT affect the speedometer calibration.

    OP: for reference, your rear end is a Chrysler 9.25". You can verify this by looking at a small tag on the driver's side axle tube:
    http://dodgetruckworld.tenmaga.../DemonXanth/306206.jpg
    http://dodgetruckworld.tenmaga.../DemonXanth/306207.jpg (9.25" 3.55 "trac lock")

    You'll need about two and a half quarts of fluid to replace your fluid, but it's a pretty easy job. You can check the fluid by simply removing the plug on the cover and sticking your finger in the hole. Also note that a possible culprit is the carrier bearing.
     
  14. iamwiz82

    iamwiz82 Lifer

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    I am an idiot and not sure why I posted that, because I know (and knew) you are right. My only excuse was is that I was tipsy at that point. :eek:
     
  15. Subbaculcha

    Subbaculcha Member

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    Not necessarily...when I swapped gears on my 96 mustang gt, I had to change out the speedometer driven gear (at the transmission) to get my speedometer in sync with the new gears.
     
  16. bctbct

    bctbct Diamond Member

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    I just had the same symptom on my 05 1500 and it was the pinion bearing. Mine was covered under drivetrain warranty.
     
  17. cardiac

    cardiac Platinum Member

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    I think bctbct hit it on the head. Find a good transmission/differential shop and have them check it. They can replace the pinion bearings and new axle seals for about $300 or so.....

    Bob
     
  18. bctbct

    bctbct Diamond Member

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    Check warranty because mopar has many different age/mile restrictions.