Differentials.. 75w-90 vs 75w-110

Discussion in 'Towing' started by mistaake, Nov 29, 2018.

  1. mistaake

    mistaake Real Name: Michael

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    I want to switch to AMSOIL Severe Gear in both the front and rear diffs. I don't tow or haul with my truck frequently, but I might be installing a camper shell and heavy toolbox, and I might tow (rarely) in the future.

    It seems like the ideal solution would be 75w-90 in the front diff and 75w-90 in the rear diff, but I'm wondering if I could get away with 75w-90 all the way around for the sake of only buying one type of gear oil.

    What viscosity do y'all run? Thanks!
     
  2. 454cid

    454cid Sooper Pooper

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    Synthetic 75w90 is OEM after early 99... go with that. 110? Never heard of it.

    Also edit your post, you typed the same weight everywhere.
     
  3. df2x4

    df2x4 Domestics only.

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    Not sure why you're wanting to switch honestly. Not saying Amsoil makes a bad product or anything but non-synthetic ACDelco GL5 80W-90 has done just fine in both of my trucks. It's what GM recommends for these. Granted I don't tow much at all but I beat the everloving crap out of the ten bolts, and the one in my red truck ran the original gear oil for almost 80K miles before I finally had it changed if I remember correctly. G80 still works. (Knock on wood)

    Here's a link, I run this in both of my trucks. Front and rear in the Suburban. NO friction modifier! Very important to make sure you're using gear oil that doesn't include any if you have a G80.

    https://www.amazon.com/gp/product/B007Q10F3S
     
  4. 454cid

    454cid Sooper Pooper

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    That's expensive for less than a quart.

    I think some of the gear oil in my truck is older than the truck... stuff that my uncle has stored under his workbench. I was running out of what I had left of my 2 gallon jug from TSC.
     
  5. Supercharged111

    Supercharged111 I'm Awesome

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    I've long wanted to take the plunge to synthetic myself as it flows better in cold weather. My mpg drops noticeably in the winter and my right foot can feel the increased drag. I would stick with the stock weight, or as close as possible. Based on your usage triple digit viscosities would be a waste.
     
  6. mistaake

    mistaake Real Name: Michael

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    Sorry, I do see I made that typo. And thank you I'll just buy 75w-90 all the way around for simplicity's sake.
     
  7. Schurkey

    Schurkey I'm Awesome

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    The Amsoil will have "positraction" additive already in the product. Not suitable for G80.
     
  8. df2x4

    df2x4 Domestics only.

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    Good to know, I'm not familiar with many of their products. Never used any of their oils.
     
  9. Schurkey

    Schurkey I'm Awesome

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    Oh, yeah...one more thing. Synthetic lube is SAID to be not suitable for axles made before a certain date--probably '99, as you said, because the synthetic lube attacks the silicone sealer at the ends of the axle tubes. Later axles have a gasket instead of sealer. Removing the sealer and installing the gaskets supposedly "fixes" this problem.

    Is this realistic? I don't know. It would have never occurred to me if I hadn't read it in the axle service manual. And nobody is saying WHICH "synthetic" caused a problem--so maybe this was restricted to a certain brand of synthetic, or a certain class of synthetic lube.

    I'm fairly sure my 1992-ish 9.5 "light duty 3/4 ton" axle got Amsoil synthetic lube in it five years ago, and that's LONG before the gasketed axles were made. But then, I also didn't know about the Posi additive, and shortly thereafter that my G80 quit working. I have plans to yank the drums and rear cover, clean-out the Amsoil lube, and re-fill with non-Posi mineral lube. There's some evidence that the G80 may come back to life once the posi additive comes out of the clutches and dissipates into the remaining lube.
     
  10. 454cid

    454cid Sooper Pooper

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    "at the ends of the axles tubes".... I'm confused on the location. The only gasket I'm aware of, is not really on the tubes, but between the axle shafts and the hubs, in the case of a full floating axle.

    I'm not familiar with semi-floating axles. I can't picture where a gasket would go, assuming you're talking about a flat paper type gasket.
     

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