Differential Oil Change and replace with??

Transmission and Drivetrain Tech

  1. gdizzle

    gdizzle Well-Known Member

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    Might anyone give me any pointers on changing out the diff. oil on my slant? It is the only fluids I haven't looked at yet. From what I can tell it is 9 hole, so that means 7 1/4? How do I know if it is Posi? It says in the manual Posi require some other kind of lubricants??

    There isn't much room to get at those top screws, backing up pretty close to the gas tank. There is no tag. In general the pumpkin looks wet with oil. I see the fill hole, if I remove it should I be able to put my pinky in there and touch oil?

    Lastly, what grade oil would I need? Living in Southern California.
    Also there is a brake line that seems to be connected to the cover screw.
     
  2. 318willrun

    318willrun Utube channel 318willrun

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    Jack both rear tires off the ground and with the car in neutral (front tires blocked, of course) spin the rear tire by hand. If both tires spin the same direction, you have a posi (sure grip). IF when you turn one tire they go in the opposite direction, the it's a single trac, one legger, non posi, or whatever other term there is :D
    If it's a "posi", it will need an additive or a gear lube already mixed for a posi.
    I'm sure 75w-90 would do you justice.
     
  3. TrailBeast

    TrailBeast AKA Mopars4us on Youtube

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    Just an FYI a 7.25 takes about 1 1/3 quarts, so you'll need two bottles to fill it. :D
     
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    • 383Scampman

      383Scampman Well-Known Member

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      Use GL-5 gear, 75w-85 or90 weight . I f you live in a warmer climate use 85w-90 or 95. If you have a limited slip differential an additional friction modifier is needed . It is an additive that should be added either before filling or mixed with gear lube until level is reached . Ford has the best friction modifier imo
       
    • kiss

      kiss Well-Known Member

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    • fratzog lover

      fratzog lover Well-Known Member

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      If its a GM unit it's a posi. lol
       
    • Woods74

      Woods74 Broke Senior

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      ^This. Ford is Limited slip, Chrysler is sure-grip.

      Don't let it happen again.. :D
       
    • gdizzle

      gdizzle Well-Known Member

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      thanks you guys. I jacked it up and spun, they spin opposite each other. So I guess that means it is Non-positive, so the normal oil will do. Is there supposed to be a small amount of "play" when you spin one wheel? before the opposite one spins?
       
    • TrailBeast

      TrailBeast AKA Mopars4us on Youtube

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      Yes, there is a lot of slack to take up between all the gears going from one direction to the other.
       
    • gdizzle

      gdizzle Well-Known Member

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      So changed the oil today. Pretty easy except for trying to remove the old gasket from the cover. Impossible. Tried all sorts of sprays, even tried soaking a few minutes in brake fluid. which did finally loosen up some of the gasket, but also removed the paint as well.
      Thanks for all you help.
       
    • RustyRatRod

      RustyRatRod I was born on a Monday. Not last Monday. FABO Gold Member

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      90 weight. With additive if it's a sure grip. Jack it up by the third member, put stands under the rear frame rails. Let the rear end down and you can get to all the bolts easily.
       
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