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Np205 mating with TH400

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Batmanjr, Jul 26, 2001.

  1. Batmanjr

    Batmanjr 1/2 ton status

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    I have a np205 with the figure eight style adapter that used to mate with a SM465. I'm going to convert my Blazer to an automatic and want to put in a Th400 cause I was told they're the strongest transmissions made by Chevy. Will my NP205 mate with it, or do I need to find a round style NP205 for my TH400. Secondly, I've heard TH475 are the absolute strongest, but they're not four wheel drive units. How hard would it be to mate one with a NP205 or is it even possible?
     
  2. thatK30guy

    thatK30guy 1 ton status Premium Member

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    You will need an input shaft to convert the 10 spline to the correct 32 spline the 400 has.

    You will also need the correct adaptor to mate the 205 to the 400. I have a brand new one from GM. Pics of this adaptor are on my home page. Check out <a target="_blank" href=http://community.webshots.com/user/thatk30guy>http://community.webshots.com/user/thatk30guy</a> and click onto the 'parts' section.



    <font color=blue>Daddy told me while learning to pee......"if you shake it more than twice, then you are playing with it!!!"</font color=blue>
     
  3. Batmanjr

    Batmanjr 1/2 ton status

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    Which Adapter is it? I'm going to tear down whatever NP205 I use and put the strongest spline posible in it. What is the strongest simpleist combination? And do you ThatK30Guy think a doubler is needed for a all time off road vehicle? What does it gain me and how does it work exactly? What modifications will I have to do? Do you have a picture or drawing of one set up? Thanks
     
  4. thatK30guy

    thatK30guy 1 ton status Premium Member

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    Those 4 pics of that adaptor are the same piece at different angles. Its the 400/205 'tall' adaptor, which means it sits on the 'flat' crossmember.

    Someone told me on this site, in order to convert a 10 or 27 spline shaft to the 32 spline, you would need to buy a shaft from someone like 4XHeaven for around $150. Then you would have to machine the input bearing bore to fit a slightly larger bearing to fit that shaft in. A machine shop can do the work for this.

    As for the Doubler, I have no experience with it. I will leave that question to be answered by other members who ARE running them. I believe a Doubler is someone's own opinion to whether they want one or need one. Of course, I would like to have one too someday. The $$$$ factor is limiting me for now.

    <font color=blue>Daddy told me while learning to pee......"if you shake it more than twice, then you are playing with it!!!"</font color=blue>
     
  5. Batmanjr

    Batmanjr 1/2 ton status

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    Does that adapter go to a figure 8 np205 or the round style np205? Or does it make it so you can use either? How hard do you thinkit would be to match a 205 to a th475? How much do you want for that adapter? Thanks.
     
  6. thatK30guy

    thatK30guy 1 ton status Premium Member

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    First of all, you have an 'older' 205 that uses the 'figure 8' adaptor. You cannot use the newer 'round' style at all. You would have to use an adaptor like the one I have pictured on my site.

    GM has 2 years of splits on the t-case and adaptors.
    The 73-84 are all 'tall' adaptors and sit on the 'flat' crossmember.
    The 85-91 are the 'short' adaptors and sit on a 'double-hump' crossmember.

    You can use older with newer providing you have the proper adapter. But the 205's cannot exchange adaptors from old to new. Hence the 'figure 8' and 'round' adaptors will not mate at all.

    My adaptor I have pictured is BRAND NEW, it cost me $200. I can sell it for $175 shipped to your door.

    Mating a 205 to a 475 is just as easy as mating to the 400. The 475 come out of motorhomes. They have a straight cut planetary gear pattern. The 400's have an angled cut pattern. The straight pattern is obviously stronger than the angled cut.

    So, to make your 205 work with a 400, or 475, you need an input shaft and bigger bearing, plus machine work to the housing, an adaptor like the one I have, and a flat crossmember (pre-'85).

    If you were to buy my adaptor, get the input shaft and bearing from 4xHeaven, and have the machine work done, you are looking at approx. $400. Ballpark figure. Then you would have to do the driveshafts.

    <font color=blue>Daddy told me while learning to pee......"if you shake it more than twice, then you are playing with it!!!"</font color=blue>
     
  7. Batmanjr

    Batmanjr 1/2 ton status

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    You're a GOD!!! I can't afford your adapter right now, but when I get into the drivetrain, I'll see if you still have it. Thank you for all your help. What do you think of "Low Gears" from Klune-V Ind.? It's just a gear box that bolts in between the Trans and the Transfer that allows you two more lower gears like a doubler. Ever heard of it? They say it's fully warrented against breakage.
     
  8. thatK30guy

    thatK30guy 1 ton status Premium Member

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    I can't say much about the Klune-V, as I don't know much about them and have never seen one. Only have read about them. That would be something to ask others on this forum, or even on pirate4x4.com. I wonder if those guys know more about them.

    <font color=blue>Daddy told me while learning to pee......"if you shake it more than twice, then you are playing with it!!!"</font color=blue>
     
  9. Batmanjr

    Batmanjr 1/2 ton status

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    Thanks I appreciate all your help.
     

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