Edmunds Answers



  • karjunkie 04/26/10 9:10 am PST

    Ford Explorer Rear End Whine/Hum
    TSB 05-12-6


    2002-2005 Ford Explorers
    2002-2005 Mercury Mountaineers


    Some vehicles listed above may have a whine/hum during acceleration, deceleration, and/or cruise.


    Use axle repair kit to fix the issue. This kit should be used instead of installing a complete rear axle assembly. Replace the Ring and Pinion and it's components.

    NOTE: When servicing the rear axle on these vehicles, replace the 75w-90 gear oil with 75W-140. If the axle is equipped with a Limited Slip, add the required amount of friction modifier (XL3). When replacing the fluid, replace metal tag with F3TZ-4121-AA tag.

    Kit Part Numbers:

    • 8.8" 3.55 Gear Ratio - 5L2Z-4209-AA
    • 8.8" 3.73 Gear Ratio - 5L3Z-4209-C

    Time: 6.6 Hrs for Explorer/Mountaineer

    I agree with Eaton advice that you need to replace the ring and pinion gears and the bearings. Apparently the problem was caused when Ford did not press the bearings incorrectly causing movement in the gears and the resulting whine.


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