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NP205/208 question

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by the professor, Feb 18, 2003.

  1. the professor

    the professor 1/2 ton status

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    Since for the moment..my K20 is staying a 3/4t 4x4
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    I do have another question for you really bright folks out there
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    I was looking at the NP208/700r4 in this burban I got...
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    I wanted to use the 208 behind a TH350..for now, AND the 700 when I get a chance to rebuild it..
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    But something didn't look right
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    My 205/27spline/th350 unit.. uses a fairly long adapter..with a connecting sleeve..and a male input shaft
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    With that, the th350 (and 700's) uses a special short 4x4 only, output shaft
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    Looking at the 208, it too seems to have a fairly long adapter to the trans too, 3 or 4".
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    long enough to use a regular "short shaft" 350 or 700 2wd output shaft...!!!
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    Its been years since I had one out of a vehicle, and I seem to remember the trans/transfer adapter as almost just a ring with the mount on the bottom...and I have seen 208's on the floor without the adapter...
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    I seem to remember the input shaft was female, flush with the front of the alum case...which would mean I would need a long output shaft
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    There IS a point to all this
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    What I was wondering, before I pull this thing out..
    Does a TH350 (or a 700r4), with a NP208 use the same output shaft as with a NP205...? i.e. a 4x4 shaft, or does it use the 2wd shaft...
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    In other words, can I drop my 205, and bolt the 208 up..??
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    Or did they change something in the later models (1987)
    /forums/images/graemlins/cool.gif /forums/images/graemlins/truck.gif
    -
    I hope this makes sense, I will retype it if it doesn't
     
  2. imiceman44

    imiceman44 1 ton status

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    It's all the same but one inch longer.
    To put a th350 with the 208 you will need 1" extension to the shaft or change the shaft to a longer one.
    Most people deal with it the opposite way, they go with 700 and 205, so they cut 1" off or put a one inch spacer.
    /forums/images/graemlins/thumb.gif
     
  3. the professor

    the professor 1/2 ton status

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    Thanks..I thought it looked something like that..
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    I haven't pulled it yet, does the input shaft stick out some..??

    It would have to , because a TH350 4x4 shaft is really short..
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    I guess I'll wait till I do the trans...
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    I wanted the 208 because:
    it is about a million pounds lighter, and easier to get in and out..
    I believe its syncro...
    I don't do any rock climbing, just some sand, hard packed and gravel
    I have a friend who does, and wants my 205..I just rebuilt it, bearings, seals shift fork, input shaft...offered good bucks..
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    I don't use a TH350 any more, after about 3years, it blew a planetary and I built a TH400 with a 2.71 first

    But it has a 27spline output and adapter...so effectively it is a th350

    The 400/205 must weigh about 700 or more pounds, my jack sunk into the asphalt of my driveway when I put it in

    gas is getting soooo expensive, and my engine spins about 2700 to 3000 rpm on the freeway, I thought I might do a 700 with the 208..since I have it...,

    I am not sure if it will hold up, got conflicting reports..B&M says NO..TCH says yes...Hughes says yes...don't know who to believe..will just have to give it a shot...(You got any idea..??

    Other choice is to make it a 1/2t w/3.08 gears...but don't want to have to buy wheels tires, and will miss the big brakes...

    But I wanted to try the 700, IF it holds up, I can convert my 400 back to 2wd..I have another 454 that I want to put in somthing light... /forums/images/graemlins/cool.gif /forums/images/graemlins/truck.gif
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    1978 K20
    1989 burban front clip (all the details)& doors
    1989 burban bucket seat, console, dash, tilt, comboswitch
    overhead console radio
    2" body
    6" chassis
    1989 454 4bolt crate motor
    eddlebrock manifold, 800 q'jet
    headders
    all ca smog equip, dual cats x-over 2.5 in throuh
    crane cam &springs
    roller rockers
    MSD billet HEI dist
    MSD 6a /remote coil
    TH400 (wide ratio 2.71 first gearset)
    14bolt, corporate, floater...3.73:1
    2200rpm converter
    NP205
    33-12.5x16.5 mud tires
    16.5x9.75 chrome spoke wheels
    =====================================================
    One thing I completely forgot, as a reason I am indifferent about the 205

    With my engine, and 3.73 gears I NEVER use lo-range

    I have had an 1800 lb, cab over camper...at OVER 10,000ft..climbing 45deg grades without even a strain in High
     
  4. sled_dog

    sled_dog 1 ton status

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    darn you I was about to ask if you would sell the 205 real cheap and you said your friend was getting it.
     
  5. imiceman44

    imiceman44 1 ton status

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    You say you have a th400 with a 27 spline output?
    Is that an aftermarket output shaft or what?
    Does it have a 4 hole or 6 hole adapter?
    I have heard of a th350 with 6 hole adapter but that was in 2wd form I think it was 1978-79.
    I think they said it was a th375.
    I hear a lot of contradicting stories but I sure would like to have some proof, if it's a stock thing can you get some pics?
     
  6. the professor

    the professor 1/2 ton status

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    For reference..a TH375 is a FWD trans, used in the later small body Rivs and Toros

    Just like the TH475 is for the earlier big body FWD cars...
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    I am using the TCI adapter plate (4-bolt/350 to 6-bolt/400) and the "cut down and resplined" 27 spline output shaft..It was the cheapest $250
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    Advanced Adapters makes one, but its about 2x as much..

    Advance Adapters also will supply you with an $800 kit to change you NP to 30 spline..It has a NEW OEM TH400 adapter and linkage, .BUT you still have to machine the transfer case for the new bigger bearing...and cut 1" off a TH400 2wd shortie..output shaft..anyway
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    Cheapeast way to use 30 spline...TCI adapter plate...get transfer case gear and bearing (about $250), and machine the transfer case, cut output shaft to stick out 4.5" /forums/images/graemlins/cool.gif /forums/images/graemlins/truck.gif
     
  7. R72K5

    R72K5 Banned

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    dont forget the 425 also
     

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