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Overfilled NP208?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mattman, Nov 15, 2002.

  1. mattman

    mattman 1/2 ton status

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    Interesting problem. I was draining the fluid on the NP208 on my '87 Blazer. When I pulled the FILL plug (the top plug), fluid gushed out. The question is how is this possible? There are no leaks around the t-case or in the auto (it has a 700R4) to t-case adapter. Also, after draining it completely it looks about 2 or so quarts more than the 5 quarts that is supposed to be in there.

    Thanks for any help on this one.
     
  2. bajaviking

    bajaviking 1/2 ton status

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    I remember someone on this board mentioned that more oil is better so he lifts the end of the truck when filling the transfer to get more oil in it. I don't know if that really is good or not but that would be a way to fill it over the normal level.
     
  3. mattman

    mattman 1/2 ton status

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    That could help explain it. Two things I forgot. One is I did this on level ground. The second is this vehicle is a rollover, so I don't know if that has any thing to do with it.
     
  4. 74Chev

    74Chev 1/2 ton status

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    I think I wrote about this in a reply to another post but I can't remember. You are suffering from the infamous 700r4 to 208 internal adapter leak. What is happening is the transmission fluid is leaking past the seal in the adapter inot the transfer case which also takes ATF. I have seen this many times. Just pull the top plug every few months and drain off the excess then top off your tranny. Do not purposely overfill any gearbox as mentioned in the other post. This not only puts excessize drag on the gears and internal moving parts but can also cause bad leaks. Most seal and vents in diffs, t-case, etc, are not designed to deal with an overfilled fluid level. Hope this helps.
     
  5. Marshall

    Marshall 1/2 ton status

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    What could have happend is actulley what i have done. when i was changing my t-case fluid i backed my blazer up on some ramps, raising the rear end so i could get the fluid in the t-case alittle better. This changes the angle meaning more fluid could fit in it. when i lowered it i had then opened the fill plug to level it out and then came out about 2-3 quarts.hope that helps
    Marshall /forums/images/graemlins/k5.gif
     
  6. mattman

    mattman 1/2 ton status

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    So is this a leaking seal on the back of the tranny? The reason I ask I am planning on using this transmission in front of a NP241. If there is a seal I need to replace, then I can do it when the tranny is out.

    Thanks a bunch.
     
  7. 74Chev

    74Chev 1/2 ton status

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    Yeah, you will definitely need to replace the seal when doing the swap. You will see it between the tranny and the adapter plate.
     

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