TH400 to 700R4 swap

Discussion in 'The "Juice Box"' started by jhems17, May 17, 2019.

  1. jhems17

    jhems17 Well-Known Member

    Hello everyone. Maybe I missed it as I searched the threads but has anyone done a TH400 to 700R4 swap? I've seen the swaps to 200-R4's but not the 700. Is there a reason for this? Is it due to the 60 torque rating behind a BBB? Also how about the 4L80E, how much work goes into putting an electronic tranny in a non electronic car? Worth it for the extra gear or not really? Thanks in advance.
  2. flynbuick

    flynbuick Super Moderator Staff Member

    Factory stock, I suspect that you will see those trans are rated for engines with outputs significantly less that 400 foot pounds of torque.

    Another solution is to keep your TH400 and install a gear vendors O.D. unit. Ask Larry. I recall the cost is 2K or more.
  3. jhems17

    jhems17 Well-Known Member

    Oh yeah, I remember reading that post a year or so ago. I even looked them up. Thanks for reminding me of that option.
  4. Luxus

    Luxus Gold Level Contributor

    I'm curious to these replies too. The 200 R4 is equivalent to the TH350 I believe, but I do know they can be built plenty stout.
  5. jhems17

    jhems17 Well-Known Member

    Yeah I was reading that too. It seems like the Gearvendors is a good option. Pricey but strong and smooth. I just looked at their website.
  6. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Besides the lower torque rating of the 7004R, that trans only comes in a Chevy bolt pattern, so you need an adapter. It also has a big drop between 1st and 2nd gear (3.06 to 1.62), not the best for performance even though the 3.06 is a nice low 1st gear. It would need to be beefed up to go behind a healthy BBB if you wanted to race the car.

    Yes, it is worth the extra gear if you do a decent amount of highway driving. The 4L80E needs a standalone controller (computer) to run it. I's a very nice transmission, basically a THM400 with an overdrive and lock up.
  7. jhems17

    jhems17 Well-Known Member

    Thanks, I was wondering why you don't hear much about it and that's why. I use the Riv often and plan on using it way more as I fix it up so the extra gear will be nice. That Gearvendors is pricey but I like what I've read so far. That's a long way off though so we'll see what happens when it's time.
  8. TexasT

    TexasT Texas, where are you from

    2004r is an easier swap but you do need to find the "right" builder . The 2004r bolts to the Buick engine and when swapping from th400 the cross member doesn't have to move. Both the 700r4 and 2004r will require a tv cable. This is NOT a kick down and MUST be installed and adjusted correctly or your trans wont go far . The 700r4 has a big sun shell that only takes about 5-600hp and you break it(even the hd ones). The 3-4 clutches are also a problem but there are ways to make em work. The 2004r has a "delicate" forward drum shaft that will take about 400hp but a lot will want to "dual feed" the direct clutches and that will pretty much require a billet shaft FWD drum as this dual feeding effectively doubles(or more) the fluid volume that is applying the direct clutches.
    The other deficiencies of the 700r4 are mentioned above.

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