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Dana 70 oil weight? (also, gaskets)

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Cubey, Jun 12, 2019.

  1. Cubey

    Cubey Full Access Member

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    What is the oil weight you guys run in your Dana 70 rear axles? I have a sneaking suspicion that it potentially has never been changed, so I want to do so very soon. If it has ever been changed, it was probably 15-20 years ago. How do you tell if it's limited slip? Just put a synthetic with LS in it to be sure?

    Also, is the capacity the same on Fords as Dodge, etc? Dodge is the main info I'm finding online for Dana 70s.
     
  2. chillman88

    chillman88 Supporting Member Supporting Member

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    No Dana 70 experience here but if it's your motorhome I would just put some 75w-140 synthetic in it. Capacity should be the same or very close, the axles should be very similar regardless of what particular brand they might be in. I would plan on changing your seals soon, I'd bet chances are they'll start leaking with new fluid, just seems to be how my luck goes anyway.
     
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  3. Cubey

    Cubey Full Access Member

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    Yep, the motorhome. I was thinking 75w140 sounded right.

    Another question that's a little off topic from the original question, but still related to the task.... anyone happen to know what the difference is between the black diff cover gasket and the blue one, both made by Fel-Pro? They are identical except for the color and price? Is the black one thicker or something? Seems odd they would bother to make two identical parts but in different colors and one twice the cost.

    dif-gaskets.jpg


    Source:
    https://www.oreillyauto.com/shop/b/...d/e-350-econoline?q=Differential+Cover+Gasket


    Also... which is better: paper plus ultra black RTV better, or this cork/metal carrier one? Do you still need to use RTV on that?

    https://www.oreillyauto.com/detail/...0-econoline?q=Differential+Cover+Gasket&pos=3
     
  4. chillman88

    chillman88 Supporting Member Supporting Member

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    Can't help you on the gasket question sadly. I always use black RTV by itself.
     
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  5. Cubey

    Cubey Full Access Member

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    Looking very close at the pictures, certain ones are thinner around the edge (for a larger ring gear) than others. I need to try to ID the axle for certain before I go buy the gasket since there seems to be 2 different Dana 70 ring gear sizes, 9.75" and 10.54".

    Spicer makes 2 different gaskets also, but they run $28-33.

     
  6. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Or just buy both and use the one that works. Return the other and jot down in your notes which you have. That's a trick that took me WAYYYYY too long to learn...
     
  7. Cubey

    Cubey Full Access Member

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    Nah, they tend to come in sealed boxes. I'd have to tear the box open to see what it is, thus not being able to return it. It would be a 50/50 chance that the first one I open will be the right one.
     
  8. The_Josh_Bear

    The_Josh_Bear Full Access Member

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    Ah you're right, I forgot the big gaskets come in those sealed cardboard boxes. Wish I could help but I don't know anything about a Dana 70...
     
  9. Cubey

    Cubey Full Access Member

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    What do you guys use for your differential covers? Paper gasket + RTV or just RTV alone? Just wondering if spending $12 on a paper gasket is really worth it. It's a Dana 70 so it should have the 10.54" ring gear. Some Dana 60 gaskets claim they fit Dana 70 too, as mentioned in the thread above, but if I can skip spending $6-12 plus tax, I may as well, if it's not really needed. The only difference is it might be easier to seal up faster, less curing time before I refill if I just put a thin layer on both sides of the gasket, instead of trying to make a gasket out of RTV alone.
     
  10. chillman88

    chillman88 Supporting Member Supporting Member

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    As I said earlier, I just use black RTV by itself. I usually wait overnight but I know some people don't wait and have no issues with it.
     
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  11. Cubey

    Cubey Full Access Member

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    Oh, yeah. Well... being that I want it to dry ASAP, I might go with paper. I am going to wait until I'm at a truck stop or Wal-Mart to do it, so I can have it on pavement for getting under there.

    I'm slowly buying the oil (Valvoline 75w140 synth), adding 1qt to online orders to get me free shipping on other items I need. I got one from Walmart along with groceries a couple weeks ago. I just ordered another from Amazon with an anode rod for my water heater (some idiot put a plug in, no rod!) and step drill bit for drilling a 7/8" firewall hole for the water temp gauge sensor to pass through.
     
  12. chillman88

    chillman88 Supporting Member Supporting Member

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    Yeah if you really want to, you should be able to get gasket paper at any parts store and cut your own. I used a paper gasket once with rtv and it leaked, BUT I was dumb and used blue RTV which doesn't have the oil resistance the black does.
     
  13. Macrobb

    Macrobb Full Access Member

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    Get some Permatex 1-minute-gasket. It either comes in pressurized cans or a caulk-gun tube. The stuff is amazing - I use it for anything that needs a gasket to stay(t-case to trans, diff cover, front cover of engine etc). It says you can just put it on, install the part and immediately return the vehicle to service. I've done just that... and no issues.

    It does get full strength after 24 hours(and that full strength is really amazing), but it seals immediately.
     
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  14. Cubey

    Cubey Full Access Member

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    I don't know that I like that the stuff comes in an aerosol type can. It would probably be murder to remove later on. I think I'd rather go with regular black RTV and just wait overnight to refill. It's 2-3x as expensive as RTV too. But thank you for the suggestion.
     
  15. DaveBen

    DaveBen Supporting Member Supporting Member

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    Black RTV.
     
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