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Thread: Diagnosing high frequency front-end vibration

  1. #1

    Default Diagnosing high frequency front-end vibration

    Jeep in my sig.

    Short version: I'm experiencing a high frequency vibration at highway speed. It starts to be noticeable at about 70, is worse at 72 and goes away at about 75. By "high frequency" I mean it isn't a wobble, I don't feel it through the steering wheel. I mainly hear it and see it in the rearview mirror shaking/blurry. The vibration goes away when I remove the front driveshaft. I've replaced: ring & pinion, pinion bearing and driveshaft. I've also balanced and rotated the tires and had an alignment (although I don't have the numbers from the alignment).

    I'm really pulling my hair out on this one and it's getting pretty expensive. My Jeep and I are currently in Florida and I definitely don't want to drive it back north with this vibration. I know there are some smart and experienced folks here so figured I would ask and see what happens. Any suggestions would be greatly appreciated.


    Longer version: My front driveshaft locked up (probably not my fault), leading to a bad vibration and bad pinion bearing/seal. Driveline shop rebuilt the DS and replaced bearings/seals, after this was the first time I experienced the high frequency vibration. The driveline shop rebalanced the shaft (twice) but the vibration didn't go away and they eventually said it must not be in the diff/driveshaft and that I'd need a 4x4 shop to look at it. I kept driving the Jeep and the vibration got worse (this one was definitely my fault). 4x4 shop replaced R&P, bearing, seals, etc. Back to just the high frequency vibration. I ordered a new driveshaft since that's where this all started and swapped that in, but no change.
    2015 JKURHR 6MT - Rancho 4" Crawler short-arm w/RS9000XLs, Yokohama G003 35s, 4.56s, Quadratec AL skidplates, Smittybilt X2O 10k

  2. #2
    Rubicon's Avatar
    Rubicon is offline Ex-Coordinator & Ex-Mod Certified Trail Leader
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    Lightbulb My thoughts / $.02

    So if you pull the front axle now, does it still have the issue?
    If does not, then I would suspect transfer case.
    If it does, I would suspect font axle.
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  3. #3
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    Default

    Has the short end of the new driveshaft been removed since purchase? Is it possible the shaft is out of phase (could be 180 out)?

  4. #4

    Default

    Quote Originally Posted by Rubicon View Post
    So if you pull the front axle now, does it still have the issue?
    If does not, then I would suspect transfer case.
    If it does, I would suspect font axle.
    Vibration is gone when the driveshaft is removed, so yeah I'm pretty sure it's somewhere in the front end. I'm just not sure what up there could cause a vibration like this.

    Quote Originally Posted by MitchConley View Post
    Has the short end of the new driveshaft been removed since purchase? Is it possible the shaft is out of phase (could be 180 out)?
    I've got two front DS now. One was rebuilt and balanced by a local driveline place and the other is brand new from Adams. Both exhibit the same vibration.


    Thanks for the input guys!
    2015 JKURHR 6MT - Rancho 4" Crawler short-arm w/RS9000XLs, Yokohama G003 35s, 4.56s, Quadratec AL skidplates, Smittybilt X2O 10k

  5. #5
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    Default

    Quote Originally Posted by Rubicon View Post
    So if you pull the front axle now, does it still have the issue?
    If does not, then I would suspect transfer case.
    If it does, I would suspect font axle.
    I also suspect the transfer case front output. Under normal conditions, it spins with the front driveshaft as it gets driven by the front tires (when you are in 2wd). It simply free spins.

    If you've gone through the entire front axle and are sure the bearings and driveshaft are good, including ujoint angles (double cardan shafts require 0 degrees at the pinion for smooth operation), then I would take a look at the transfer case. The front output is usually driven by a chain, which could get damaged and cause issues. When you remove the front shaft, that front output stops spinning (until you put it into 4wd).

    - Is the front output bearing smooth and free of play?
    - Does the case have oil?
    - Does it still vibrate when 4wd is engaged (with AND without the shaft)?
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