Gear oil, 1996 Z71

Discussion in 'Chevy Truck Forum' started by kd7ctv, Dec 15, 2017.

  1. kd7ctv

    kd7ctv Full Member

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    #1 kd7ctv, Dec 15, 2017
    Last edited: Dec 16, 2017
    So my rear differential seal is leaking so that needs to be replaced. No worries there. However I know it calls for 80w90 gear oil in it. But can I use 75w90 in it without damaging it.?

    Never mind, it was cheaper to get a gallon of 80W then three bottles of 75W. So I'll stick with what's recommended.
     
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  2. MikeG

    MikeG Full Member

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    Can never go wrong sticking with what's recommended.
     
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  3. jkeaton

    jkeaton Full Member

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    Word.
     
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  4. dirtrider73068

    dirtrider73068 Senior Moderator
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    I concur if it calls for 80w90 go with it. 80w is weight or could be the 90 is weight Its been a long time since I learned about this in school. Its best to go with it calls for, I tried to go with a 20w 50 motor oil in a old truck before and found out real fast in winter its not goo and had to change it out to 10w50.
     
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  5. leolkfrm

    leolkfrm Full Member

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    if it is posi, put the additive in the gallon so you maintain it as you add
     
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  6. kd7ctv

    kd7ctv Full Member

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    I have the G80 in it. And there is a TSB that says don't add any additive so I wasn't going to add any to it. From the TSB. 'The use of any additive in locking rear axles (G80) is not recommended. Rear axle additives are designed for use in limited slip differentials which are normally installed in cars. All light duty trucks equipped with RPO G80 make use of a locking differential and the use of additives will delay the engagement of the locking mechanism and may decrease axle life."
     
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  7. leolkfrm

    leolkfrm Full Member

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    VEHICLES AFFECTED: ALL LIGHT TRUCKS EQUIPPED WITH G80 REAR AXLE ALL YEARS
    Some light duty trucks equipped with locking rear axles (G80) may exhibit rear axle chatter, especially when turning a corner from a stop.
    This condition of alternate engagement and disengagement of clutches in differential assembly is usually caused by contaminated axle lubricant.
    To correct this condition, drain and refill the rear axle with SAE 80W-90 GL5 (P/N 10950849

    i believe gl5 has the additive so it does not smell in the mm4 and 5 tranny too

    its why i posted posi....sometimes i wander between car and truck...lol
     
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  8. kd7ctv

    kd7ctv Full Member

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    It's all good. As long as it works that's all that matters to me..lol I'm pretty sure I changed it once already when we got stationed down here, but now I have to fix the leak before we move and I tow a trailer 600 miles.
     
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  9. kd7ctv

    kd7ctv Full Member

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    So torque specs for the cover bolts I'm seeing is 30ftlbs, is that right? I didn't see anything official on it, just a bunch of people posting different numbers but 30 was the most consistent number
     
  10. leolkfrm

    leolkfrm Full Member

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    i generally tighten to" firm ", book says securely.....that said,
    if using any rtv make sure it is the one for gear oil, depending on make the one i get is a green tube...
    .i prefer a gasket and contact sealer like copper gasket, seals small scratches and hold the gasket in place
    biggest thing is getting surfaces clean, i like lacquer thinner or brake clean as it leaves no residue, gear oil is nasty and hard to clean
     
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