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gm400 to 700r4 swap

Discussion in 'The Hokey Ass Message Board' started by hotrodderjoe, Jun 22, 2012.

  1. hotrodderjoe
    Joined: Nov 27, 2010
    Posts: 22

    hotrodderjoe
    Member

    Hi
    I'm not over familiar with the gm transmissions. I'm looking at swapping current gm400 for a 700r4 mainly to get the overdrive. The gm400 is currently on a 235 chevy with a Stovebolt conversion kit. So my question is ..Will a 700r4 bolt straight onto where the gm400 was ar do i need to do some other mods? I've found plenty of threads discussing length of transmission and ratios but none about bolting the thing on !

    Cheers, Joe
     
  2. 41hemi
    Joined: Jul 2, 2007
    Posts: 931

    41hemi
    Member

    The bolt pattern is the same for both trans if they are Chevy. I think the lengths are different. Your adapter will work......
     
  3. Here are some dimensions that might help
     

    Attached Files:

  4. It's direct bolt up!

    You may need to shorten your driveshaft and move the tranny crossmember back a tad.

    You will also need the necessary "proper" brackets that mount to the carb for the T.V. cable. Always keep in mind that it is a T.V. (throttle valve) cable and NOT a kickdown cable. If you, like so many others, think it's a kickdown cable you will smoke the tranny in very short notice. The T.V. cable is there to regulate line pressure and must work and be adjusted properly.
     
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  5. squirrel
    Joined: Sep 23, 2004
    Posts: 44,327

    squirrel
    Member

    The driveshaft yoke will need to be changed too. TH400 is larger than the 200. You may need to change the length of the driveshaft, depending on what yoke is on it now and what yoke you get.
     
  6. Uh squirrl, he's going to a 700R4 not a 200.

    Not sure if it matters but it might.
     
  7. nutajunka
    Joined: Jan 24, 2007
    Posts: 1,466

    nutajunka
    Member
    from North Indy

    Plus some 700r4's are set up for an electronic speedo, but you can change that pretty easy with the right parts.
     
  8. squirrel
    Joined: Sep 23, 2004
    Posts: 44,327

    squirrel
    Member

    400 uses a big yoke, while the PG, 200, 350, 700 all use a small yoke.
     
  9. Cool! I was unaware of that.

    I should have known "never question the squirrl"! :D
     
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 44,327

    squirrel
    Member

    It's ok to question me, I have about a 80% correct answer rate here on the hamb.

    And maybe someone will comment that the TH375 has a small yoke.
     
  11. 80%????

    Now you're just being modest.

    I wish I had 1/2 your knowlage.
     
  12. 28chevrat
    Joined: Oct 11, 2005
    Posts: 322

    28chevrat
    Member

    Like it was mentioned before make sure you set up that T.V. Cable, it's important. If not you'll smoke that tranny.
     
  13. Joe, Inliners.org has some fairly detailed instructions that come with they're adapter but if the 400 was already mounted Im betting your already in pretty good shape. Since the topic seemsto come up alot lately, I'll ask are you guys using a specific 700R4 ? The yards here are loaded with em,but Ive noticed small differences from different cars. I'd like to put one in my wifes 60 Chevy behind the stock 235.
     
  14. Yes!

    They must be a 30 spline input shaft 700R4. Preferably an "MD8" case or a "K" case. A 4L60 (not 4L60e) is the same tranny.
     
  15. squirrel
    Joined: Sep 23, 2004
    Posts: 44,327

    squirrel
    Member

    ...pretty much any of the large bellhousing (v8) transmissions from around 1985-1992, right?
     
  16. It's '87 and up.

    2 wheel drive S-10 pickups too
     
  17. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,502

    gimpyshotrods
    Member

    Only those that had the 90º V6 (4.3l). The 60º V6's and the 4-cylinders have a different bellhousing pattern.
     
  18. hotrodderjoe
    Joined: Nov 27, 2010
    Posts: 22

    hotrodderjoe
    Member

    Thanks for all that help guys. I haven't got a transmission yet. I wanted to do some research first. I'm OK with doing crossmember and prop mods if necessary but it's good to know a 700r4 will bolt straight on where my gm400 currently is. I presume the torque converter will bolt straight on will it? I've got a few other long term projects on so didn't want this turning into something that took more than a couple of weekends. I'll have a look at the lengths and see if there's a way I can get away without a new prop. Thanks for the tips on the TV cable...I'd probably have found out about that too late the expensive way! Cheers, Joe
     
  19. Be aware that starting in 1988 they go to electronic speedometer drive - Chevy Suburban and vans kept the mechanical another year or so (my 1989 is mechanical), I think each line that used the trans has a different cutoff year - which means some dicking around to swap back or buy a big money drive box to use it with your stock speedometer.

    A 700R4 is about 6" longer and the trans mount needs to move back 4" - I don't know if they're a good candidate in an X-frame car like a '60 Chevy.
     

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