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  1. #1
    Member stevolwevol's Avatar
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    Default Differential fluid change

    I am preparing to replace the differential fluid in my 79 (Eaton). I've read some say always use GM additive, and I've also read using NAPA etc is fine also. Is there a real difference? Is there such a thing as too much additive? My plan is Valvoline GL5, plus NAPA additive. Input would be helpful.

  2. #2
    Administrator Tom Bryant's Avatar
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    I've never used anything other than GM lubes. The part numbers have changed over the years but the product is what is recommended for a GM posi rear axle. If the other brands meet the same specifications they should be alright. I can't say from experience though.

    GM AC Delco Axle Lubricant 89021669

    GM AC Delco Fluid 88900330 Limited Slip Axle Lubricant Additive.
    NCRS 1360.............SACC 2082.............C1 Registry..............L81 Registry
    1959 Chevrolet Corvette 1981 Chevrolet Corvette , 350 L81 automatic Frost Beige

  3. #3
    Member stevolwevol's Avatar
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    Quote Originally Posted by Tom Bryant View Post
    I've never used anything other than GM lubes. The part numbers have changed over the years but the product is what is recommended for a GM posi rear axle. If the other brands meet the same specifications they should be alright. I can't say from experience though.

    GM AC Delco Axle Lubricant 89021669

    GM AC Delco Fluid 88900330 Limited Slip Axle Lubricant Additive.
    Thank you Tom, I ended up taking the big leap and used the NAPA stuff. The differential and posi work fine. Thanks again.
    Likes Tom Bryant liked this post

  4. #4
    Member douglasamariani's Avatar
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    Default

    A
    lways use GM additive

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