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xfer case fluid - ATF to gear oil?

Discussion in 'The Garage' started by ascuro, Sep 3, 2006.

  1. ascuro

    ascuro Registered Member

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    I'm planning on switching my NP205 fluid from ATF to gear oil - how concerned should I be about cleaning out all the remaining ATF? Would a simply drain and fill be enough?

    I'm guessing there shouldn't be any problems with a little remaining ATF in the case, but better to ask and be sure :wink1:
     
  2. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    Does it really matter which one you use?
     
  3. yoshisv

    yoshisv 1/2 ton status

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    I thought NP205's are suppose to run gear oil anyway. I have always been told to run gear oil in cast iron cases and ATF in aluminum cases. I could be wrong though.
     
  4. ascuro

    ascuro Registered Member

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    Yeah, pretty sure they're supposed to be filled with gear oil - ATF isn't supposed to hurt though, but mostly I want to see if it'll fix the tiny amount of seepage I'm getting from the shift rail seals (I can't seem to find these sold seperately, only as part of a master rebuild kit). Since gear oil is a bit thicker, I'm assuming it should help.
     
  5. jamber2541

    jamber2541 1/2 ton status

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    np205 uses gear oil, np203 uses motor oil, np208 and newer aluminum cases use ATF
     
  6. Chevy305

    Chevy305 6 Lug 14bsf Status Premium Member GMOTM Winner

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    Wait how much fluid does say the NP208 take?
     
  7. 4by4bygod

    4by4bygod 1/2 ton status

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    Why do you want to change to gear oil? Don't get hung up on a " thicker oil means more protection" mindset..a higher viscosity lubricant doesn't equate to higher film strength, or the ability to absorb more heat.

    Tom
     
  8. u2slow

    u2slow 1/2 ton status

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    FWIW, I looked into the factory spec'ed oil for my '91 crew (465/205 combo) and it was Dexron 2 ATF.

    I put gear oil both and found it to shift nicer, and a little quieter.
     
  9. sandawgk5

    sandawgk5 3/4 ton status

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    Mine took just over a gallon of ATF:D

    Ira
     
  10. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    5 quarts (as listed in the shop manual).
     
  11. sled_dog

    sled_dog 1 ton status

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    wrong, to a point. The newer 205s ran ATF. ATF is thinner. If anyone is of the mind set that synthetic diff lubes and such will gain you power and mileage, then run ATF in the xfer case ;).
     
  12. K5er4Life

    K5er4Life 1/2 ton status

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    I remember reading a post about this gear oil vs. ATF and it seemed that in the factory manuals the earlier 205 required gear oil and the later model ones required ATF. not necessarily because the internals are different in any way, because to my knowledge there not, but this probably related to gas mileage more than anything. I run gear oil in my 205 in blazer (wheeler rig) and ATF in my daily driver crew cab. Dont ask me why just figured I would try it out...:dunno:
     
  13. jamber2541

    jamber2541 1/2 ton status

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    would the difference be slip yoke =ATF, fixed yoke = gear oil
     
  14. 6.2puller

    6.2puller 1/2 ton status

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    Nope, my 88 has a fixed yoke 205 and runs ATF according to the owners manual. I would bet they skimped on luberication to gain fuel mileage.
     
  15. sled_dog

    sled_dog 1 ton status

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    its not skimping on lubrication. and they didn't change internals so you could run ATF in an old one.
     
  16. RustyParts

    RustyParts 1/2 ton status

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    If you use 80 - 90 gear lube in an aluminum gearcase you stand a good chance to crack the gearcase in cold weather because of hydraulic pressures generated by the gears compressing the cold lube.
     

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