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HELP:NP208 popping out of 4Hi

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by bigerik, Apr 13, 2001.

  1. bigerik

    bigerik 1/2 ton status

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    This is driving me crazy! Truck is 1981 350/TH400/NP208 w/ original drivetrain and the NP208 will go into 4Hi and function, but it won't stay there reliably (it popped out in the middle of a mudbog event!). Once it is in 4Hi, the front driveshaft is engaged, but after driving around a little, the shifter sorta goes back to 2Hi by itself. Truck has a 3" body lift, and I even took it to a tranny shop for an inspection, new fluid and go through and tighten up/check the shift linkage. They said that there were some chunks of metal in the NP208 fluid (it seems like they always say that!) and that the t-case was ready to die. They said it might last between a day and a year. Does anybody know of a way to fix this short of buying a reman NP208 from Boyce for $695? I wonder if the shift forks are worn or if the body lift messed it up. That would suck if I put in a reman and it did the same thing due to the body lift, but I think the shifter just comes out of the t-case, so this problem appears to be internal (in the NP208). Truck has seen some hard use. Please reply if you know anything.

    <A target="_blank" HREF=http://www.bigerik.coloradoK5.com>http://www.bigerik.coloradoK5.com</A>
     
  2. Nrose07

    Nrose07 1/2 ton status

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    I'd put money on your shift fork. Its not too hard to do yourself and when I did mine the total bill was about $50. Good luck!

    Displacement, cubes, and did you say you drive a riceburner???
     
  3. bigerik

    bigerik 1/2 ton status

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    So I should pull the transfer case, open it up and I'll find a shift fork? Where would I get the replacement part? Dealer? Natl. Drivetrain? This could save me $650!!

    <A target="_blank" HREF=http://www.bigerik.coloradoK5.com>http://www.bigerik.coloradoK5.com</A>
     
  4. Nrose07

    Nrose07 1/2 ton status

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    Well yes you will need to take out the transfer case. Get yourself a Hayes manual, and if you can take pictures as you take it apart. The shift fork is in the front most part or the case. The shift fork you can get from any tranny shop of parts store, that where I got mone. Might think about doing both forks at the same time.

    Displacement, cubes, and did you say you drive a riceburner???
     
  5. bigerik

    bigerik 1/2 ton status

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    Sorry, it's me again. Would it be appropriate at that time to just do a rebuild based on my synopsis above? Also, I might add that I work too many hours to do this myself, and I'm not very mechanically inclined. So do you think I should hire a tranny shop to redo the shift forks only or score the reman from Boyce? This whole thing came up because I need a new ring gear (flexplate), and I thought I'd cure the 4Hi popping out problem while I had the t-case down. Thanks for responding.

    <A target="_blank" HREF=http://www.bigerik.coloradoK5.com>http://www.bigerik.coloradoK5.com</A>
     
  6. Espen88k5

    Espen88k5 1/2 ton status

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    Maybe of no help but my linkage from the t-case shifter on the floor to the t-case needed lenghtening after my 3" bodylift. It would quietly slip out of 4hi when the body bumped around a litle. I removed the connecting rod and switched the t-case to 4hi by hand. Messured the lenght with the rod and could see I was about 1" short. It's still not 100% and I'm thinking I need to cut out a piece of the floor to allow for more travel of the stick. That or drop the hole shifter 3".

    [​IMG] If your not living on the edge, your taking upp to much space![​IMG]
     
  7. doonjumper

    doonjumper 1/2 ton status

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    I know that u asked about 4 hi but I had the simalar problem with 4 low. The gear was used alot in its life and the teeth got worn and were no longer able to make good contact and.

    [​IMG]
     
  8. bigerik

    bigerik 1/2 ton status

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    I bit the bullet and bought a reman from Boyce for $695 with money I didn't EVEN have. I know NP208s suck with their aluminum case and chain drive. I want a Doubler, or at least an NP205, but crossmember and linkage mods cost money, and my trucks have really taken up ALOT of money...you have felt the pain...

    <A target="_blank" HREF=http://www.bigerik.coloradoK5.com>http://www.bigerik.coloradoK5.com</A>
     
  9. the shift fork has a plastic piece on the tips that wears out.

    i had a local shop here in houston go thru my unit, new seals, and chain and fork plastic thingy for 200....

    greg
     
  10. Gold Rush

    Gold Rush 1/2 ton status

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    Most of the time when a 4wd shifter pops out it's because of the linkage hitting the body. A simple 1/4 inch trim around the opening through the floor usually cures it.

    David 75K5
    http://www.extremeblazer.com

    [​IMG]
     

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