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Technical turbo 350 verses 400

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

  1. looking to see which transmission would or is a better fit I im working on building 1931 chevy sedan thanks for info . bruce
     
  2. BJR
    Joined: Mar 11, 2005
    Posts: 6,002

    BJR
    Member

    We need to know what motor is going to be in front of the transmission. After all you wouldn't want to put a 400 behind a flathead. So.... give us more info so we can help.
     
    31hotrodguy likes this.
  3. brigrat
    Joined: Nov 9, 2007
    Posts: 4,914

    brigrat
    Member
    from Wa.St.

    Not to steel the thread but what gear ratio's do the 350 & 400 have?
     
  4. figure8
    Joined: Oct 4, 2006
    Posts: 66

    figure8
    Member

    350 is lighter, more efficient and can be built to handle plenty of power. I would only use a 400 in a heavy truck or car




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  5. 40Standard
    Joined: Jul 30, 2005
    Posts: 5,751

    40Standard
    Member
    from Indy

    I like the turbo 350 tranny
     
  6. I agree with the above statements, that the 350 is lighter, and even though it is lighter, it can be modified, without spending too much money, to handle even a big block in a lighter vehicle. This is from a guy that is running a couple of TH400 trannies in my own vehicles.
    Another option worth considering, that would give you an included overdrive, would be a 700r4.
    Bob
     
  7. jimmy six
    Joined: Mar 21, 2006
    Posts: 5,191

    jimmy six
    ALLIANCE MEMBER

    200r OD same size as a 350
     
  8. anthony myrick
    Joined: Sep 4, 2009
    Posts: 5,044

    anthony myrick
    Member

    I plan on using a 350c. Cheap and simple. The lockup converter is easy to hook up.
    I used a 400 in the last build only cause it weighs over 6k. I vote 350 unless it’s gonna have stupid HP
     
  9. BJR
    Joined: Mar 11, 2005
    Posts: 6,002

    BJR
    Member

    It would be nice if the OP would chime in.
     
  10. Hnstray
    Joined: Aug 23, 2009
    Posts: 10,974

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    Early 700R4's had as many problems as early 2004R's.....both were corrected in due time. Anything rebuilt today would have the upgraded parts.

    The greater power required to overcome internal friction of the rotating mass in the 400 tips the scales in favor of the 350 in that particular comparison. That is in addition to the size and weight penalties.
     
  11. squirrel
    Joined: Sep 23, 2004
    Posts: 44,342

    squirrel
    Member

    th350 is 2.52/1.52/1.0
    th400 is 2.48/1.48/1.0

    (1st, 2nd, 3rd)
     
  12. The Turbo 350 is pound for pound and dollar for dollar the simplest transmission to run. I’ll probably run nothing but them from here on out.

    They just work so well in a variety of cars.
     
  13. Haven't seen a good reason to use a 400 in this application...so far ;)
     
    31hotrodguy likes this.
  14. squirrel
    Joined: Sep 23, 2004
    Posts: 44,342

    squirrel
    Member

    I know a guy who built a 31 Chevy sedan and the TH400 was the perfect transmission. He also used a blown pontiac engine and a clutch (clutch-turbo).

    It didn't really work very well, but it was the right trans for the car!

    (in other words, yeah, we need to know a lot more about it before helping you make a decision)
     
    chryslerfan55 likes this.
  15. I wouldn't even consider a 350 or a 400 when 700s are readily available. Makes any car so much more drivable. Lower first gear, taller 4th. ........
     
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  16. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,722

    mgtstumpy
    Member

    A friend has a T400 in his small GM Vauxhall behind a 350SBC crate engine. Way too much parasitic drag for a stock light weight car. I've advised him to trade up to T350, better all round than a 400 in what he has. A 200 or 700 would be better for economy however you need to have the right ratio rear axle to make it worth it, something low, 3:9.1.

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  17. InstantT
    Joined: Aug 15, 2012
    Posts: 656

    InstantT
    Member
    from SoCal

    Bruce's 31 Chevy and mgtstumpy like this.
  18. Joe H
    Joined: Feb 10, 2008
    Posts: 794

    Joe H
    Member

    You also need the right hp and torque curve to run an overdrive transmission. Not all engines are suited to run OD.
     
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  19. 19Eddy30
    Joined: Mar 27, 2011
    Posts: 979

    19Eddy30
    Member
    from VA

    350 great transmission , But it comes down to what weight , Power , torque & what you are trying to accomplish , Im running 350 behind my model A,
    Will be switching to glide to calm Down , knocking tires off from 1st to 2nd (63mph )& 2nd to 3rd (80mph) gear shifts , Over 100mph in 1/8 not Single track,& is street driven .
    I am running a 3:42 gear on 29 inch tall tires with a very tight converter locked @ 1,325 rpms , weight under 2,700
     
    Last edited: Apr 19, 2019
  20. 1934coupe
    Joined: Feb 22, 2007
    Posts: 3,525

    1934coupe
    Member

    For what it's worth I agree completely and I too have run 400 turbo's.

    Pat
     
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  21. OLDSMAN
    Joined: Jul 20, 2006
    Posts: 2,071

    OLDSMAN
    Member

    I've got a 400 TH behind the 455 Olds in my convertible, but I'm putting a 350TH behind the small block I will be putting in the 42 Chevy I'm building for my daughter
     
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  22. In a small car like the Chevy or Ford for that matter the 350 is a smaller transmission and room is at a premium when trying to install all the exhaust, pedals and so forth. HRP
     
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  23. porknbeaner
    Joined: Sep 12, 2003
    Posts: 41,391

    porknbeaner
    Member

    I prefer 400s personally. But there is an added caveat that the T350 has over the T400. If you run the long tail T350 to start with and decide that AOD is just as traditional (or just want an OD) the 700R4 is a bolt in. No new driveshaft, no now mounts and no modifications to the hump.
     
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  24. 56sedandelivery
    Joined: Nov 21, 2006
    Posts: 5,925

    56sedandelivery
    ALLIANCE MEMBER

    Another vote for the TH-400! Here's why; my D.D. had the 700R4 go out at 16K miles, a TH-350 then went in as no one knew how to work on the 700R4 at the time, as they were still so new (we were out of town, on the road in California). GM paid 85% of the back-date for that swap. Well, that TH-350 did't last but a couple of years, and then another went in, and it too only lasted a couple of years. Just regular, pick up truck driving, without any towing. So, a TH-400 went in. Talk about night and day! No lag between 2nd and 3rd gears that the TH-350 has. Solid, but not harsh shifts, not mushy like the TH-350's had. No worries about the weak sprag assembly of the TH-350 (break that and the whole trans has to be rebuilt-did that with another car) either. I was so impressed with the difference between the two transmissions, I went out and bought another TH-400 for any future project/need. I actually have another Chevrolet truck with a 454/TH-400 in it also. We were still in "the recession" at the time, and guys were selling rebuilt transmissions they had for projects cheap; hard to make it when they were't working. I only paid $250.00 and $200.00 each for both rebuilt TH-400 transmissions, with converters. Now, I do have a couple of TH-350's on hand, but I also have the stuff to beef them up where GM fell down on them, mainly the sprag assemblies; I have a new drum with the 36 element TH-400 style sprag, and a diode type sprag adapted from some of the Ford products. But, as far as a DD or truck goes, TH-400 for the win, all the way, all the time, all day and night long. The so-called 40 HP loss the TH-400 reportedly has, makes no difference on the street; if you're racing, then every little bit helps. That's my opinion, from a lot of experience with both the TH-350 and TH-400 transmissions. I really wish I could come across an old cast iron, Dual Range Hydra-Matic, with all the small parts such as kick-down/TV pressure linkage, for a Chevrolet application, but I've given up on that dream since I unloaded, for FREE, all my Hydro stuff 25 years ago; I still regret doing that, stupid, stupid, stupid. I am Butch/56sedandelivery.
     
  25. BJR
    Joined: Mar 11, 2005
    Posts: 6,002

    BJR
    Member

    Big engine's need big transmission. My 472 Cad in my Buick came with a 400 trans. Don't think a stock 350 could take the HP & torque of a 472 Cad engine. (375 HP, and 525 ft lbs torque at 3000 rpm)
     
  26. If you want to spend the money, you can build a TH350 to handle 700 or more HP, all it takes is money. I know that Ken Bell used to build units that could handle 800 hp all day, but when you can go the the auto wrecker and pick up a TH400 for less than $200, sometimes the easier way is to just go to the wrecker.
    If your intention is to regularly run it on the track, the TH350 will require more routine maintenance. If you are concerned that you are putting out a lot of HP, then you really need a TH 400. Here are some useful links.
    Almost anything is possible, if you want to throw lots of money at it.

    http://www.superchevy.com/how-to/sucp-1302-as-real-as-it-gets-th350/

    A primer on selecting and building a suitable automatic transmission
    https://www.skipwhiteperformance.com/tech/transmission-choice/

    https://gearstar.com/transmissions/gm/

    Bob
     
    chryslerfan55 likes this.
  27. With this debate....... Just PERSONAL experience, and no opinions...... The TH350 is a great trans......all around. Yes- tire size,gears are a major factor, as well as intended use.
    Daily's=without a doubt, as well as warmed up hot rods...... No need to worry.
    Even the lowley powerglide......... This just seem's to be focused on a # of a trans, BUT- what is it really intended for?
    Everything mentioned has been used and beaten to death in one way/shape/form......
    Pic your gears/rpm range/tire diameter, and do a lil math......
    They ALL can withstand abuse..... But- here we go.... What will you throw at it? I believe some reading might be required,and, everything can be made to work with applications......
    Just don't shit on a certain trans just yet......... They all have pro's/ Con's..........
    You have to master your smarts before just picking because the # looks good...... Do your homework, and it will serve well..........
    Time served the hard way here....... You gotta learn sometime, and the hard way isn't pleasant, or cheap.
     
  28. The 350 is smaller than the 400. A lot depends on the rear end gear. How big an eng. (H.P.). A good all around choice is the 700r4 . same size as the 400 and has overdrive. Last year I built a 32 Ford with the 700r4 and 350 fit fine.
     
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  29. 19Eddy30
    Joined: Mar 27, 2011
    Posts: 979

    19Eddy30
    Member
    from VA

    X2
    Im running 350 be-hide 600 plus hp With alot of Torque, not a high dollar trans just decent quality parts for over 4 years , has over 20,000 miles on plus every time drive car it get 2 hard pulls , and 100-150 miles of street driven , 3 - 4 times a week.
    I also run 400's & one of my Glides is a $$ trans.
    It just depends on Application , a good cooler is a must. Heat kills
    You can build a 700 r4 now that will hold around 600hp & Torque
     
    Last edited: Apr 19, 2019
    chryslerfan55 and INVISIBLEKID like this.

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