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700R4/NP 208 adapter

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by BANKO, Mar 16, 2003.

  1. BANKO

    BANKO Registered Member

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    I'm planning on swapping my TH400 for an aftermarket 700R4 in my 85 k20. I assume the 'burbs of this same model rear use 3/4 running gear and 700R4 trannies. Is this true? If they don't, can I use an np208 adapter off an 85 k5 and just re-drill the mounting holes in my cross member?

    Thanks, Josh
     
  2. BANKO

    BANKO Registered Member

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    Anyone?

    Maybe I should re-post this in the general discussion section.

    -Josh
     
  3. outlaw612

    outlaw612 1/2 ton status

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    A couple of problems with this idea.
    1) The t-case wont work for ya, the th400 case is 32 spline and the 700r4 is a 27 spline.

    2)The 700r4 is longer than the th400 so you will need to drill new holes in the frame for the crossmember.

    3) Since the 700r4 is longer, it will move the t-case back so you will probably need new front and rear driveshafts

    The easiest thing to do would be find a donor vehicle and get the trans, t-case, adapter, shifter, linkages, and driveshafts.
     
  4. DieselBurb

    DieselBurb 1/2 ton status

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    [ QUOTE ]
    A couple of problems with this idea.
    1) The t-case wont work for ya, the th400 case is 32 spline and the 700r4 is a 27 spline.

    2)The 700r4 is longer than the th400 so you will need to drill new holes in the frame for the crossmember.

    3) Since the 700r4 is longer, it will move the t-case back so you will probably need new front and rear driveshafts

    The easiest thing to do would be find a donor vehicle and get the trans, t-case, adapter, shifter, linkages, and driveshafts.


    [/ QUOTE ]

    1- You can find adapters to go from 32 to 27 splines
    2- the crossmember should be fine (I think). The trans/transfer case adapter should make up the difference in length.
    3- If you have a 208 now, the shafts should be okay.

    My 85 /forums/images/graemlins/burb.gif had a 700R4 but someone replaced it with a TH400. I know the stuff I wrote above because I have looked into swapping back to the OD.

    Diesel /forums/images/graemlins/burb.gif
     

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