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700r4 to np205 questions..

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by shaggyk5, Jun 12, 2001.

  1. shaggyk5

    shaggyk5 1/2 ton status

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    Ok, I know we've discussed this all before, and i have done a search, but im still not sure. Here's the situation.

    My best friend is buying my 700r4/208 from my 85 blazer, to put in his 79 pickup. he wants to keep his 205 t'case though. his 205 is behind a th350 now, so what else do we need to get/do to put his 205 on my 700? Just an adapter plate? or is a tailshaft swap in order? thanks in advance guys.


    --matt
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  2. wayne

    wayne 3/4 ton status

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    You need to swap the output shaft on the tranny. I was looking into doing the swap on my 89 but I want to keep the lower ratio so I plan a 241 slip yoke eliminator and a 1350 joint cv shaft.

    <A target="_blank" HREF=http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html>http://jamonline.homestead.com/fromthegroundupK54x4/89Jimmy.html</A>
    <font color=blue>Happy Trails<font color=blue>
    <font color=blue>Wayne<font color=blue>
     
  3. BIGJ

    BIGJ 1/2 ton status Author

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    You need the original adapter from the TH350 and 205. You also need the shorter output shaft from AA. New holes will also have to be drilled in the frame for the crossmember.

    BIGJ
     
  4. ROY

    ROY Registered Member

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    I used an adapter block for a 700r4 to turbo 350 conversion and cut 1/4'' off the 700 output shaft. you will have to use the adapter for the 350 to 205 and make a plate for the t/c shifter if you want it to come up in the stock location. This is a cheap and easy swap. I have done several of these swaps and have had it in my 87K30 for 4 years with no problems. If you have any questions you can email or call at 843-257-4332. ROY

    BIGREDGMC
     
  5. shaggyk5

    shaggyk5 1/2 ton status

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    ok, so heres what im getting....

    i have the adapter for the 350 to 205. (this is the combo he is running now.) i need to replace/shorten the output shaft on the 700, and then they bolt up? cool. what is involved with replacing the output shaft? does cutting the shaft like Roy suggested cause any problems?

    --matt
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  6. mpascino

    mpascino 1/2 ton status

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    how do drive shafts work out then? i know the rear has to be done, what about the front?

    You call that dirty!?
     
  7. Leadfoot

    Leadfoot 1/2 ton status Premium Member

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    The 700R4 is a longer tranny (which pushes the t-case back)so the front may have to be lengthened and the rear shortened. When I did my first 700 swap on a longbed pickup it was real easy. There was an extra set of holes that lined up from the factory for mounting the crossmember furthur back and we had just installed a 4" lift so the drive shaft actually ended up needing to be the same length as the stock unit without the lift so we didn't touch it. The front shaft was really short (from the lift and t-case being moved back) so I had a spare that we lenghtened. In some cases where there is no lift involved, you can buy a flange spacer to make up the difference, but lengthening the driveshaft is the better alternative (plus by lenthening the shaft rather than using a spacer, you have less of a driveline angle)

    If you didn't built it yourself, how can you call it yours.......?
     
  8. bigblue

    bigblue 1/2 ton status

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    Why go with the 205 ? I think the 208 is kick ass. It is lighter, much better gear ratio and if it breaks just carry a spare with you! Now a doubler and you are talking !
     
  9. BIGJ

    BIGJ 1/2 ton status Author

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    Some people have said that to replace the output shaft requires complete dissassembly of the tranny. When I did this swap I dropped the tranny myself to save on labor (the bench rate was cheaper). It was around $100 to put the new shaft in.

    BIGJ
     
  10. shaggyk5

    shaggyk5 1/2 ton status

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    im not worried about moving the x-member or re-doing the driveshafts, i know about all that. Im just worried about hooking up the 205 to the 700. does anyone know anything about cutting the output shaft like the guy said earlier?


    --matt
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  11. Ryeguy

    Ryeguy 1/2 ton status

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    Check, I really believe that you don't have to replace the TH700 output shaft with an A/A part, if you aren't against doing new driveshafts (which you'll have to do anyway). Like someone already said in this thread, what you should need is:
    - unmodified TH700R4
    - NP205 from a TH350
    - adaptor for that NP205/TH350 combo
    - spacer (about 1-1.5" thick) to go between the adaptor and the TH700R4
    - longer bolts to tie it together
    - maybe a brace like the NP208 has back to the engine

    We did this to mount a TH350 version of an NP203 behind a TH700R4 with no prob's. Since we haven't done it with a NP205 (everyone 'round here using these parts is going dual T-case straight off) I can't say for sure, but I can't see why it wouldn't work.

    That spacer is lots cheaper ($10 for the one I know about) than buying the A/A shaft and having it installed. But you'll have to relocate the Xmember and deal with driveshaft lengths.

    --Rob
     
  12. josephn

    josephn 1/2 ton status

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    THAT IS COOL.
    WHERE WOULD YOU GET A SPACER?

    1982 6.2L Diesel K5 Blazer, TH700, 31 inch tires.
    Fire ALWAYS makes it better.
     
  13. Ryeguy

    Ryeguy 1/2 ton status

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    Made it. It's pretty simple. Basically a donut with a couple steps in it to align the adaptors, and 4 holes for the bolts to hold it all together. Cost included the scrap piece of aluminum I found, plus a litte bit of lathe time.

    A/A doesn't want you to do this, and won't sell you the adaptor (and tell you it won't work). They'd rather sell you an expen$ive transmission shaft than a simple, cheap spacer.

    --Rob
     
  14. josephn

    josephn 1/2 ton status

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    COOL.
    COULD YOU BY CHANCE SEND ME A ROUGH DRAWING?

    1982 6.2L Diesel K5 Blazer, TH700, 31 inch tires.
    Fire ALWAYS makes it better.
     
  15. Ryeguy

    Ryeguy 1/2 ton status

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    If you want, I will. But it really is as dead simple as it sounds. O.D. is so it will completely cover the end of the transmission. I.d. is same as the adaptor. Make a step the same size as the adaptor, so it "looks" like the adaptor as far as the trans is concerned. Put the mate to the step on the other end so it "looks" like the trans from the other side. And drill 4 holes through it so you can bolt the adaptor to the trans.

    It's just a big donut with 4 holes in it, with a couple steps to make it "compatible" with the adpator and trans.

    --Rob
     
  16. josephn

    josephn 1/2 ton status

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    Cool.
    I think I know what to do know thanks. :)

    1982 6.2L Diesel K5 Blazer, TH700, 31 inch tires.
    Fire ALWAYS makes it better.
     
  17. Ryeguy

    Ryeguy 1/2 ton status

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    Just be careful about how you measure for the thickness that the "donut" should be, so that you get full spline engagement there. Make it the thickness required for the TH700R4 output shaft to extend beyond the housing the same as the TH350.

    --Rob
     
  18. ROY

    ROY Registered Member

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    you can buy this block from your local trans shop. It is for putting a turbo 350 in place of a 700r4. I used to buy just the block for about 35.00 but the company must have gotten wise now they offer it in a kit which includes the dipstick,flywheel cover,longer studs andthe block for about 90.00 I'll try to get the company name and part # thursday ROY

    BIGREDGMC
     
  19. ROY

    ROY Registered Member

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    Hey shaggy I got the part # for the block. Its made by Tech-Pak and the # is 7q-35a, 4x4 Quik swap kit I got these #'s from pt's transmission in charleston S.C. ROY

    BIGREDGMC
     
  20. shaggyk5

    shaggyk5 1/2 ton status

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    cool. so this is the PN for the spacer that goes between the trans and the adapter? can i get this anywhere else besides this place in S.C.? (im in philly)

    --matt
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