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Technical turbo 350 verses 400

Discussion in 'Traditional Hot Rods' started by Bruce's 31 Chevy, Apr 18, 2019.

  1. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,065


    Actually the 700R is the same size as a T350. The 400 has a large case diameter. The 400 will take a lickin and keep on tickin but the down side if any is that it is a resource hawg. It takes more torque to use a T400 that a T350. Most of the time it is not noticeable, and we are probably talking about .001s of a second on the 1320. So not anything that most of us are going to be too worried about.
    chryslerfan55 and INVISIBLEKID like this.
  2. Still don't know the specific application yet, so while we're busy bad mouthing perfectly good transmissions, I'll just wait for the o/p's response.
    swade41 likes this.
  3. ^^^^^ YEP! All about the ratio's I guess. Well, know. What works for one, might not work for another....
    I'm gonna ditch my 700r for several reasons, but that's not what this thread is about. We can discuss privately.
    350 vs 400= If people did the math, gear ratios, tire diameter, final drive with calculated rpm and speed, it would be a given.. Of course our engine has to live up to it to maximize.....
    Sometimes instead of covering your eyes, and throwing the dart, well you know(general)...... I know you know.
    chryslerfan55 and 19Eddy30 like this.

  4. Physically some what....... But- The mounting is 3'' longer than a 350. Make's it a P.I.A if someone wants to switch back.........X-member, possibly lines, and the dreaded driveshaft re-do. Get's a lil costly....
    Hope guy's do their homework before realizing...... Just my OP.
    chryslerfan55 and 19Eddy30 like this.
  5. I have both the 700r in one car and the turbo 350 in another. Truthfully, running around town there’s not much difference. Yes, the 700r has the overdrive but in a classic vehicle that’s as aerodynamic as a brick that’s not as much of a plus as some would think.

    Most of the time I’m cruising in the right hand lane at 60 - 65 because the car just doesn’t handle right in the wind at anything above 70. And the turbo 350 will do that for less than half of the overdrive transmissions.

    I don’t know anything about the 400’s.
    Last edited: Apr 19, 2019
  6. 19Eddy30
    Joined: Mar 27, 2011
    Posts: 905

    from VA

    Failure of 700R4 most of the time , cable not adjusted Correctly.
    chryslerfan55 likes this.
  7. putting a chevy 400 in
    swade41 and chryslerfan55 like this.
  8. putting a chevy 400 in,
    chryslerfan55 likes this.
  9. thanks for all your replys everyone,
    OLDSMAN likes this.
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 43,481


    funny thing is this is the HAMB, the 400 came along in 1965 (in chevys), the 350 in 69, so there's one other consideration if you like making cars sort of like they used to be, at some particular point in time.
  11. boltupal
    Joined: Dec 27, 2010
    Posts: 257

    from western ny

    Automatic transmissions are a communist plot.
    mkubacak likes this.
  12. The th350 is a fine trans
    Nothing wrong with it and I’d run it if it’s already there or if I knew it was good.

    However if I’m building or going to spend money it would be on the th 400.

    The 700 is ok in the right application because that 1-2 shift just sucks! If I just had to absolutely have an OD auto it would be a 200 built up.

    Fuel consumption and Mpg need to put against the total miles driven before calculating cost benefits.
    chryslerfan55 and BJR like this.
  13. indyjps
    Joined: Feb 21, 2007
    Posts: 3,576


    Question for the transmission rebuild experts. How does cost stack up TH400 to TH350 for different power levels.
    400, 500, 600hp? Is it a wash?
    When do you need to start moving up to sprag, drum, pump upgrades and manual valvebodies.

    I priced it all out 20 years ago, but theres a lot more stuff available now.

    TH400's are getting harder to find. I should put one on the someday shelf. Next to the someday BBC'S. I have managed to grab a short tailshaft and guts if I need to convert a long TH400.
    chryslerfan55 likes this.
  14. Okay, and then? Horsepower level? Nitrous, blower? slicks ? No burnouts or drag strip?
    All of this stuff matters to get the answer you're looking for..
    Jeez ..Happens every day here ;) indexpt.jpg
  15. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,065


    The long tail T350 and the 700R are a straight swap. no new mounts needed.
    We do it all the time here. Which usually means I get a T350 core or a 700 when someone wises up and says, "Gee the 700R is just not what I wanted." LOL
    19Eddy30 and chryslerfan55 like this.
  16. I see said the blind man! Thanks for the clarification....... I guess when doing these things,planning takes a back seat.......I don't see too many ,if at all, long tail 350's used all that much, at least around here. But a guy would be real smart-:rolleyes: to know that, and leave an escape route for the "just in case"scenario.......
    Learned something new here! Thanks B!
    19Eddy30 and chryslerfan55 like this.
  17. I would go th400 for the mere fact that you will never hurt it, it is one tough transmission !
    With that being said I do have 2 cars with th350's, one I don't worry about because it's only around 400 hp and 1800lbs, the other I am a bit worried about because I replaced the built stroker small block with a healthy stroker big block. I tell ya it's in the back of my mind and I haven't even got the project finished yet.
    I do have 2 with th400's, one with a blown big block and the other will be a 355 but it's in a truck that will be used as a truck, towing and hauling things and I have no worries about these two.

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