Ford F-250 SD Differential/Gear oil.

Discussion in 'OT Driven' started by Thought Thinker, Apr 5, 2009.

  1. Thought Thinker

    Thought Thinker Circling the drain.

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    01 Ford F-250 SuperDuty 4x4, lifted on 35's.
    Rear end has 4.56's in it (new) need to change oil since break in.
    Tow pig, work truck, gets beat on a lot.
    In the Texas Panhandle, gets pretty warm, and pretty cold.

    Anyone know the ins and outs regarding differential/gear oil?
    I think factory weight is 75w-140. Should I stick with that?
    Go a little heavier in the front, maybe 75w-110?

    Trying to find out what my best bet would be.
    Any knowledge is appreciated.
     
  2. CastorTroy

    CastorTroy New Member

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    75/140 would be the best to stick with. 75/110 is going to be thinner than 75/140, not heavier. Thinner may give you slightly less resistance, ala slightly better mileage, but at the cost of increased wear. Also if you have a limited slip diff, don't forget the additive for that.
     
  3. borazhasleftthebuilding

    borazhasleftthebuilding Lets Party OT Supporter

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    20f isnt cold for diff oil,son
     
  4. borazhasleftthebuilding

    borazhasleftthebuilding Lets Party OT Supporter

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    i can be -40f one day, and 100f 5 days later

    stock diff oil is all we use

    40,000 lb rears
     
  5. deusexaethera

    deusexaethera OT Supporter

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    I'd go for the 75-110 instead of the 75-140, or else get something with a higher cold weight if you want the 140 hot weight. Oils that aren't straight-weight (i.e. the ones with two weight numbers) have chemicals called pour-point depressants mixed in, and they cause the oil to behave like it's a lighter weight than it really is when it's cold.

    That sounds great, and under normal use it isn't a problem, but those pour-point depressants wear out with age and start affecting the oil's weight when it's hot too -- so the 75-140 will actually be more like a 60-90 after a couple dozen thousand miles, whereas the 75-110 might be more like 70-100.

    Rule of thumb: the smaller the weight spread, the more the oil thins from heat, and the wider the weight spread, the more the oil thins from age. Since gear oil doesn't get changed very often, I think it's better to pick something that will retain its viscosity for a long time.

    EDIT: I did not google this, I asked several mechanics and a tribologist about it. :squint:
     
  6. affende

    affende Resident 4X4 Elitest Prick

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    sweet ... you just proved your point to be worthless.

    if you are changing your diff oil every "couple dozen thousand" miles, you are worthless and need to be shot.

    engine oils - 3-5k depending
    tranny, transfercase, diffs - 10-15k on the clock ... with good oil.

    my suggestion: Royal Purple 75-140 .... its the best shit i have ever used in any diff / manual transmission ....

    stick with factory weight, and dont listen to DE, he is retarded.

    texas gets hotter than it does colder ... stay with thicker oil. when you move to canada, consider thinner oil, otherwise, the SE/Souther US does not get cold enough to consider thinner oils.

    fuck man, i run thicker than spec'd diff / manual trans / transfer case oil ... and i have NEVER had a wear related failure in any of them.

    you have larger tires, and a lift, and i assume (or hope) you at least take that POS offroad .... you are putting more stress and more wear on the gears than normal highway usage ... the LAST thing you need is thinner oil.
     
  7. Bugalu

    Bugalu OT Supporter

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    and you wonder why everyone hates you.


    stick with stock weight. id rec. normal dino oil too. lots of gear manufacturers wont warrenty gears that have been run with synthetic oil since they "sharpen" the gears and cause a whining noise.

    This happened to me.
     

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