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NP 205 fluid?

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by Rasberry, Jul 18, 2002.

  1. Rasberry

    Rasberry 1/2 ton status

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    What do I put in my np205 T-case? I figured it was time to change it out.
     
  2. Batmanjr

    Batmanjr 1/2 ton status

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    Gear Oil! If you're down south I use 90-100W IF you're up North use 80-90W!
    DON'T USE TRANSMISSION FLUID!
     
  3. chulisohombre

    chulisohombre 1/2 ton status

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    do what batman said
     
  4. Kev71

    Kev71 Registered Member

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    i think i have transmission leak into my t-case, just cuz the gear oil in it isnt as heavy and seems to be diluted wiht transmission fluid. Is this a HUGE problem /forums/images/icons/confused.gif , or one i can solve by just draining the t case and puttin in new gear oil?
     
  5. ntaj*ep

    ntaj*ep 1/2 ton status

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    You can change out the fluid. But the ATF will still "drain back" into the t-case from the trans. You need to fix the o-ring in the adapter housing, so the trans fluid stays in the trans. and does not dilout/overfill the t-case. You will most lickly start to develop leaks if it persists. /forums/images/icons/shocked.gif
     
  6. 72gmc-burb

    72gmc-burb Registered Member

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    Mine has had the leak from the TH-350 tranny to NP-205 for the last five years and ~50,000 miles. The trick is to not park on a steep slope w/ the nose in the air for days/weeks! You do want to drain and fill the transfer case w/ every other oil change, and drain buildup above the filler plug of the 90w/atf mix before you take a long trip.

    If the case becomes over full and the transfer case gets hot (like running on a road trip in the summer), fluid will blow out of the vent, the output seals, and any other possible oriface.

    There is no sure bet that replacing the o-ring at the back of the tranny will stop the leak into your xfer case (like what happened to a buddy of mine w/ a K-10).

    I've had no problems with the output seals leaking or w/ bearing/gear wear because the Fluid is clean, even if it is a variable mix of 90w /atf.

    So, if you are on a budget, drain and fill your xfer case, and check it over the next couple of thousand miles to see how much you are leaking.

    Good luck!
     
  7. ntaj*ep

    ntaj*ep 1/2 ton status

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    Your buddie got the wrong o-ring the trick is to try to blow through the union. Once you get it you won't have any problem with it "draining back"

    To answer the orignal question, gear oil is the correct lube. /forums/images/icons/smile.gif
     
  8. Murph

    Murph Registered Member

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    I believe that this topic has come up before. What was said before is that GM originally specified gear oil, then changed to ATF as recommended (most likely due to the problem you are having).
     
  9. ntaj*ep

    ntaj*ep 1/2 ton status

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    What problem? I have the correct o-ring in my adapter housing, gear oil in the t-case, and ATF in the transmission. No external or internal leaks, All good. /forums/images/icons/wink.gif
     
  10. Robin

    Robin 1/2 ton status

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    Actually there are 2 seals in the adapter that keep everything seperated (you have to pull off the bearing to get to the one). What also tend to happen is that dirt gets in there (???) and causes the seals to rub grooves in the adapter shaft.

    To be safe you can buy speedy sleeves that cover up the grooves so that your new seals will work best
     
  11. Dune_Goon

    Dune_Goon Registered Member

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    OK, on the T-Case GM says to run whatever you have in the tranny. If you're an automatic then you run ATF, if you have a manual then you run gear oil. They say you do this for gas mileage and if you have a seal leak you won't mix the fluids.
     
  12. ntaj*ep

    ntaj*ep 1/2 ton status

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    Who at GM says this? /forums/images/icons/tongue.gif If you are going to run ATF in a NP 205 case are you going to replace all the seals also so the ATF is compatible with them and dosen't harden them? Since ATF has diffrent properties than gear oil, that would be a good idea............Huh? /forums/images/icons/tongue.gif Does your source at GM say to drain out the xs ATF/GL5 from the case, since the input from the transmission is higher and will hence "overfill" the NP205 case? I would like to know why "GM" says to use a diffrent fluid in a NP205 case and not replace the seals? /forums/images/icons/smirk.gif Do you have a SB# or something. This would be brand new information to me. /forums/images/icons/grin.gif
     

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