Rear End Makes Clunking Noise And Feels Loose, Grey Metallic Colored Diff Fluid

Discussion in 'SN95 4.6L Mustang Tech' started by Duanee33, Jun 26, 2013.

  1. Duanee33

    Duanee33 New Member

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    Ok I have a 98 Cobra with an Auburn diff and 4.30 gears. For a while now the gears have been "howling" they howl only when cruising (barely giving it throttle at about 40mph +. The noise is so loud it drowns out the exhaust while cruising. If I give it more gas or completely let off the throttle the noise goes away. Anyway, lately I've been hearing and feeling a clunking sound/feeling from the rear end only at very low speeds while turning. I started doing some investigating in the rear end and when I drained it the fluid that came out was a greyish metallic color. I don't mean metallic like it had metal shavings in it, it was very uniform in color but I've never seen any gear oil look like that. The diff drain plug is magnetic and did have some metal shavings on it. Any thoughts on what might be going on would be greatly appreciated.
     
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  2. Rusty67

    Rusty67 Well-Known Member

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    Sounds like nothing good. Are you sure you had the right kind of gear oil in there ? Does that Aubrun diff need friction modifier ?

    Was the gear noise caused by bearings or the ring and pinion gear ?
     
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  3. trinity_gt

    trinity_gt Advanced Member

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    I think there's no question the rear needs to come apart completely for forensics.

    I'm thinking the greyish oil is full of pulverized metal that would be the consistency of talcum powder if it could be distilled out of the oil. The source could by anything from bearing races to gear teeth but only by getting it all apart can you see what's gone awry in there.
     
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