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Tranny switcheroo

Discussion in 'Transmission & Transfer Case' started by rjohn, Sep 26, 2020.

  1. rjohn

    rjohn Junior Member

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    Can this 400 fit in my 91 burb currently has a roasted 700r4 sitting in it. Just not sure if the 400 is meant for a 4x4 or is out of a car a buddy gave it to me. It's been sitting was rebuilt says has shift kit in it.

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  2. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    That's a 2wd th400.
    BUT. Certain 400's you could remove the tail shaft housing on them and hook bolt a 4x4 adapter to them.
     
  3. rjohn

    rjohn Junior Member

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    Would the 700r4 tailshaft work on the 400 or would I have to find the actual adapter and obviously make sure my 400 will work
     
  4. Vbb199

    Vbb199 B-rate Hillbilly Customs Supporting Member

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    You'd need thr actual adapter I believe
     
  5. HotRodPC

    HotRodPC Administrator Staff Member

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    YOu will need that actual adapter and you will also need a 32 spline input on your transfer case where it currently has a 27 spline for a 700r4 or Th350.
     
  6. rjohn

    rjohn Junior Member

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    Ok so adapter I will start searching for is the input spline hard to change in the transfer case
     
  7. HotRodPC

    HotRodPC Administrator Staff Member

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    I don't believe it's hard to change at all. Also keep in mind, since that's a 2wd output shaft, due to the length, you'll need to replace that or if possible, maybe cut it off if it's splined all the way. I don't recall at the moment for sure.. To change the output shaft on the Th400, you'd have to pull the complete transmission apart since the output shaft is the first hard part that goes in the case.
     
  8. rjohn

    rjohn Junior Member

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    All this informations got me re thinking rebuild time on 700r4 lol
     
    Turbo4whl likes this.
  9. HotRodPC

    HotRodPC Administrator Staff Member

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    Probably the smarter move at this point since that's a 2wd 400 and going to need some mods and then to acquire the adapter and find or convert to a 32 spling input on the Tcase.... If I were to be doing all that for a 400, may as well source a 4L80-E and go for the big time and never look back.

    That's my intent since the 2wd 4L80-E output shaft is long enough an fully splined to where it can be cut off and used as a 4x4 Trans. So I'm going to go with my Th400 for now since I have it on hand and it's an actual 4x4 Th400 and I have the adapter and transfer case that was originally married to it. I also have the rebuild and shift kit for it. But, later plans are to go with the 4L80-E.

    By the time you have 2 700r4's built you could have just done the 4L80-E and been done with it for many years of reliability and not have to candy ass it in fear of hurting it.
     
  10. HotRodPC

    HotRodPC Administrator Staff Member

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    But.... to add... I'm on board with your decision at this point to stick with your 700r4. The good part is, if it's the original 1991 700r4, you're starting with one of the better cores. With a good builder that knows what mods to get in it at bare minimum you have a chance of some longevity if your not running oversize tires or to crazy oversize and have the proper gear ratios in the axles. The lower the better. A 700r4 will thank you alot for 4.10's or 4.56's. 3.73 isn't to bad either w/ fairly stock tires.
     
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  11. rjohn

    rjohn Junior Member

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    I do have a line on a 4L80 from a friend for 400 bucks probably needs a rebuild from sittin ya got me wondering lol I do want 35" tires believe my rear end is 3.73 but not to sure. The 700r4 is stock.
     
  12. rjohn

    rjohn Junior Member

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    Note the 4l80e is outta a diesel has transfer case with dash button shift. He said 300 for just tranny not sure on the conversion I no she will have a higher stall rate not sure if that will be a problem for my 350 tbi
     

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