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np203 to np205 swap

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by mtnsun, Nov 28, 2002.

  1. mtnsun

    mtnsun Registered Member

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    Question... I have been working on my 77 GMC Jimmy project and would like some info on swapping out the old 203 for a 205 transfercase. It will be hooked up to a T350 auto trans. The right parts? I know that there are many combos of adaptors and hookups. What is right and what will be the best ...
    Thanks,

    Jeff /forums/images/graemlins/k5.gif <font color="orange"> </font color>
     
  2. Waxer

    Waxer 1/2 ton status Author

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    What is right is the stock th350/np205 adapter. I forget the name of the shop that I ordered mine from, but I paid $100 for it. I made this swap a few years ago and it was a good one. The 205 is a much better case IMHO.

    I used my existing crossmember, just had to move it back a few inches and drill new holes in the frame for it to mount to. The crossmember required small modifying where the tcase mount bolts were, but nothing that a dremel can't handle. Other than that it was a bolt in job.

    Course your driveshafts will have to be worked on. Rear gets shortened and the front gets lengthened, if I remember correctly.
     
  3. cool2see

    cool2see Registered Member

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    Easy changeout, I did it to my 79, but I didnt have to drill any holes, but had to get different drive shaft, rear is shorter and front is longer. The adapter and shifter and shifter linkages are the hard things to find.
     
  4. 4x4Freak

    4x4Freak 1/2 ton status

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    I just did this same swap on my 79 with th350. I was lucky enough to find a t-case with adapter to fit it. The hardest part was getting the old 203 out.

    My crossmember stayed in the stock location. The only difference was that one of the 205 mount holes is narrower. This was no problem, my crossmember had a long slot in it for the mount to slide inward. I shortened the front shaft 3" but I think it could've used a little more. The t-case is a slip-yoke version; I used a 91 suburban shaft and traded it at the driveshaft shop for one that could be shortened easier.
     
  5. K5 NUTT

    K5 NUTT 1/2 ton status

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    Th350 version NP205...sleeve (between trans and tcase)... x2 seals..recommend GM for the seals...shifter and boot...shifter bolt...all still ava at gm....in fact new NP205 shift lever know comes with a built in bushing like a leaf spring to combat rattles...np205 shift rod plate...orange bushing...and link...sounds about right...then besides doing it and the square cut o ring you will need to seal the trans to the adapter its only a matter of gettin the driveshafts done....i might still have some of the small parts in the garage still....and i know i have a shift knob from a 1980 K5...the only year to come with a NP205....but i was a slip yoke unit...

    Azblazer
    Grand Junction Co.
     
  6. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    What the name of the shop?
    That is super cheap for that adapter.
    Is it something they made, and if so, what material is it made of.
    Sorry for all the ???'s but that info is very interesting.
     
  7. 4x4Freak

    4x4Freak 1/2 ton status

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    Wouldnt happen to know how much the shifter parts run would you? What about part numbers?
     
  8. 76_Cheyenne

    76_Cheyenne 1/2 ton status

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    I've been calling auto salvage places everywhere and all they say they can give me is a 203 for my Th350. Did GM make a 205 for the th350, or do I just need to find a 205 from anothewr transmission and get the adapter? thanks
     
  9. imiceman44

    imiceman44 1 ton status

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    It was a rare option but it was available behind the 350.
    Even rarer behind the 400.
     
  10. 76_Cheyenne

    76_Cheyenne 1/2 ton status

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    If I cannot find one that bolted to a TH350, What one should I ask for, like the one that bolted to the SM465, or will any GM 205 fit the adapter plate I have to buy. Thanks
     
  11. imiceman44

    imiceman44 1 ton status

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    When you say adapter that you will buy, you mean like an Advance Adapter or the OEM adapter?
    If OEM then you can only use the right TCase or you will need to buy a different input shaft and tear the TCase up and replace the shaft.
    It is not that uncommon to find the right Tcase.
    Used parts search
    This is a nice search engine for used parts.
    car parts used and this one is another.
    I am sure you can find one, just give it a couple of days and wait for the nest deal.
    I am not sure what years had that option, I know 76-77 didn't have it.
    I know in '80 205 was the only option so ask for 80 then you will get responses for what will fit.
    Good luck
     
  12. 4x4Freak

    4x4Freak 1/2 ton status

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    Keep an eye out for one on Ebay. Someone occasionally lists one on there.
     
  13. 73k10sub

    73k10sub 1/2 ton status

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    Try looking at this website: http://www.offroaddesign.com/NP205tech.htm
    My 73 K10 Sub had the TH350/NP205 combo and uses the 27 spline drive sleeve shown in ORD's article. The sleeve is 4.25 long and 2" OD. LOL.
     
  14. 76_Cheyenne

    76_Cheyenne 1/2 ton status

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    I found one in NC for 400$ shipped to Montana. Does that price seem about right? Thanks
     
  15. 4x4Freak

    4x4Freak 1/2 ton status

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    Seems kinda high to me, but maybe not. Has it been rebuilt with new bearings and seals, if so then it might be worth it. I paid $200 for mine in the junkyard.

    Send BILLYRAY a message, he did have one this summer when I was looking, but I dont know if he still has it or not. He'd gone through it and put new bearings and seals; and I think he also had the shifter and adapter too.
     

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