need help designing spacer (700r4-2-np205)

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by jekbrown, Feb 6, 2002.

  1. jekbrown

    jekbrown I am CK5 Premium Member GMOTM Winner Author

    May 19, 2001
    Likes Received:
    Vancouver, WA, USA
    hey gang. I finally got my np205 xcase....YAY!! =) anyway, all I have to do now is design a spacer that will allow me to mate the thing (along with the factory th350 adapter) to my 700r4. Just by looking at the adapter, it *seems* like a steel ring of the right thickness and with holes for the bolts/outputshaft would work a-ok. questions...

    1) anyone see any fundamental problems with this?

    2) anyone know *exactly* how thick such a spacer would be? i would think this # would be similar to the difference in lengths of the th350 and th700s output shafts....

    3) would it be wise-est to modify the shift-lever from my existing n208 to shift the new 205....or to modify the 205s lever to fit the factory-cut hole in my tub?

    4) with respect to attaching the spacer...would it be ok, in theory, the have it welded to the th350 adapter? i was thinking this might be a good idea...otherwise I'd have to have some kind of rubber seal on both ends of it right? still, I guess I'd need one where the 700 and the spacer met....should I just design that part of the spacer to look exactly like the mating point of the adapter? factory-size seals would work in that case...

    5) what kinda fluid does the np205 need? any recommendations on which brands are high-quality?

    6) how much should I expect to pay to have a shop install a x-case? the thing is heavy as way I could do it myself...rather have a pro do it. Assuming that it is complete and ready to bolt in (have the apdater, all the seals etc etc) much?

    any info/input/advice is, as always, greatly appreciated!


    See the on-going build up of my '85 Jimmy! <a target="_blank" href=></a>
  2. pcorssmit

    pcorssmit 1/2 ton status

    Jan 2, 2001
    Likes Received:
    Denver, CO
    1. The spacer would have to duplicate the 208 adapter, including and indexing diameter(s) on the front, and duplicate the 350 rear, including any indexing diameter(s), on the rear.

    4. No. The OE adapter is cast iron. Use RTV.

    5. 80-W90. Whatever the store carries.

    6. If you can't install the t-case yourself, this is probably not the type of project you should undertake. Either have the proper tailshaft swapped into your tranny, or buy a new adapter (try Advance).


    '83 K5, 350 TBI (ex 6.2), 700R4, NP208, Dana 60/14 bolt, 4.56s, Detroits, 3" lift, 15-39.5x15 TSLs
    '97 Dodge 2500 4x4 CC LB Sport, Cummins 5 spd
  3. Leadfoot

    Leadfoot 1/2 ton status Premium Member

    Nov 28, 2000
    Likes Received:
    Western Massachusetts
    1.) shouldn't be a problem if done right
    2.) Not sure
    3.) I modified my stock 205 shifter. Cut the handle, welded on a spacer and attached the top of the shift handle so it was farther forward. This allows me to cut the welds and put the shifter back to stock (with one weld) if need be.
    4.) Make one side of the adapter look like the 350/700 tailhousing, and the other look like the stock 205/350 adapter and use the same type of stock seal (big o-ring, but now you would need 2). If it works stock, it should work there.
    5.) 90 weight gear oil. 80W -90 (I think is what the label says, but I don't have it in front of me)
    6.) If they are just unbolting the t-case, bolting in the adapter, and remounting the t-case. It should be about a 1/2 hour for a good tranny shop (whatever your local rate is). Leave your t-case in 2WD and remove the shifter before you go as it will save them time, also remove the front driveshaft (saves them time and you $$). They will have to remove the crossmember, rear driveshaft (and front if you have not done so), speedo cable/sensor, t-case to tranny brace (if equipped and will have to be later modified to fit the extra length, and 4WD idicator wires. ****side note: Depending on how the exhaust is routed, you may have to make changes there as well.

    And lastly, if you do this, let us know:
    1.) how it went
    2.) how much it cost to have the adaptor made as others may be interested (you might be able to make some $$)

    See my rig at <a target="_blank" href=> click here </a>
  4. donimator

    donimator 1/2 ton status

    Jun 11, 2001
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    Tacoma WA
    Do a search on the old posts. Someone a while back used a spacer about 2in that someone makes. I wouldn't think that it would be too expensive. I can come down one day and give you a hand putting that 205 in. I have done mine at least 8 times. I know now to get it in. I have a tranny jack that I use to put it in. Just buy pizza for luch, and you have a helping hand. No shop labor cost. Let me know.

    73 3/4 ton Chevy. 383 stroker, TH350, NP 205, 14bolt FF(Detroit), Dana 44(limited Slip), 6in. lift, 36x 14.5 super swampers

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