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NP205 Fluid

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jkce457, Nov 25, 2004.

  1. jkce457

    jkce457 1/2 ton status

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    What is the proper fluid for a 1985 NP205? Both books I have say ATF, but it looks like it has oil in it? /forums/images/graemlins/confused.gif
     
  2. Hossbaby50

    Hossbaby50 3/4 ton status

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    I believe 205's are gear oil. I know the older ones are. They books you have may quote the oil for an 85 as ATF for the NP208 cases that most 85's have.

    NP205's are gear oil as far as I know. 80w-90 or what have you.

    Harley

    Does the oil in there stink like gear oil. If so then it is gear oil.
     
  3. jkce457

    jkce457 1/2 ton status

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    It definatly has gear oil in it now, but I wanted to confirm that it is the correct fluid. My 85 NP208 had ATF, and the books say that after 1980 all T-Cases take ATF? /forums/images/graemlins/dunno.gif
     
  4. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    I have two 205's. The one in my 1980 K10, with manual trans, has gear oil. The 205 out of the newer blazer (88-ish and going in the 1979 K5) that was connected to an automatic and has ATF in it.
     
  5. jkce457

    jkce457 1/2 ton status

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    So can anybody else confirm which it is?
     
  6. Poohbair

    Poohbair 1/2 ton status

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    205's are supposed to have gear oil. 208's (and pretty much all aluminum housing chain drive cases) take ATF. 203's take 30wt motor oil.
     
  7. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Not completely true. In the later years GM spec'ed ATF for NP 205s for increased fuel economy.

    I'd put gear oil in it anyway.
     
  8. jkce457

    jkce457 1/2 ton status

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    Well, it sounds like someone much have switched it to gear oil at some point. It seems to be working fine, so I guess I'll just change it out for some fresh gear oil for now.
     
  9. 6.2puller

    6.2puller 1/2 ton status

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    I would think a 205 with ATF would be kina loud on the road but I have never tried it. I have been running 80w90 for years with zero issues.
     
  10. miniwally

    miniwally 1/2 ton status Premium Member

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    The 205 and 203 have had everything from 80/90, ATF, and 30 weight speced from the factory. 80/90 is the best to put in and if you want to try for a little better milage you can use synthetic 80/90.
    ATF would work but we are putting these things under more stress than they probably imagined for a stock truck would have so 80/90 takes that stress better.
     
  11. OrangeCrushK10

    OrangeCrushK10 1/2 ton status

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    What if your running it behind and Automatic Transmission?

    Any chance on them swapping fluids?

    i.e. Gear oil leaking into the transmission, or vice-versa?
     
  12. jkce457

    jkce457 1/2 ton status

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    /forums/images/graemlins/thinking.gifHmmm... maybe that's why the gear oil didn't look quite right...
     
  13. 454k30

    454k30 1/2 ton status GMOTM Winner

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    this is a good question. My 1983 asks for ATF for my 205 but i have switched to 80-90w in order to better protect the bearings and gears. The ATF change was a feeble attempt to increase mileage. This however dries out seals and is not near as good at protecting gears and bearings. As long as the output seal on your tranny is good no fluid should swap between the tranny and the t-case.
     
  14. Blazer1970

    Blazer1970 1/2 ton status

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    [ QUOTE ]
    What if your running it behind and Automatic Transmission?

    Any chance on them swapping fluids?

    i.e. Gear oil leaking into the transmission, or vice-versa?

    [/ QUOTE ]

    It is very, very common for the tranny fluid to leak back into the t-case. That, along with mileage is the reason that they spec'd ATF in later years. The 205 will work just fine on ATF.
     
  15. Steve_87K5

    Steve_87K5 1/2 ton status

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    I have never been able to keep tranny fluid outta my 205 for very long. After a new seal it's ok for a while then back to normal. So I run same synthetic in tranny and 205. Amsoil Series 2000. That, and Mobil 1 in engine, and Mobil-1 gear lube in rearend, I would say gets me ~1 mpg gain.
     
  16. mtn. burb

    mtn. burb 1/2 ton status

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    I blew up the 208 (ATF) replaced it with a 205 behind TH400 - gear oil - 90W.
     
  17. RiceDaddy

    RiceDaddy Registered Member

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    I run 80W90 synthetic gear lube in my NP205 in my 1980 K5.
     

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