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Thread: TH350 vs. TH400

  1. #1
    MaineShark's Avatar
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    Default TH350 vs. TH400

    Simple enough question: what's the difference between the TH350 and TH400?

    Are there any benefits to having one vs. the other?

    Joe

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    Member safety_match's Avatar
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    I don't remember the specfics from my youth, but I do remember that the TurboHydro 400 was a much beefier and stronger transmission. Much more suited to handling higher powered vehicles.

  3. #3
    Gone but not forgotten Mad-Mic's Avatar
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    th 350 = light weight able to handle upto 400 hp

    th 400 = heavier unit handles over 600 hp

    both got to be built right. with a th 350 you can actually electronically lock up the torque converter to get an overdrive out of it from what i was told when looking for a 4 speed auto.

    the 400's you'll find in the big block cars and drag strip cars mainly. although a th 350 will suit most needs the 400's can be brute monsters and can be built nearly bullet proof.

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    Joe,
    Mad-Mic is right, the 350 is strong and the 400 is bullet proof. the big difference in the trannies is the gearing. first gear on the 350 is slightly lower than 400. i think they are 1.56 vs. 1.48 respectively. second and third gears are the same. some guys say that the 350 doesn't rob as much power as the 400, but i could never tell the difference. the ultimate auto tranny is the 400 with a gearvendor od. brian

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    Thanks. I wasn't sure if they simply had different ratios, or if the durability was different.

    I searched for the ratios and found this site. Do those look right?

    I think the ultimate is actually a TH400 with GearVendors and a conversion to a lockup torque converter... power and economy

    Plus you can tell everyone you have a 6-speed.

    Just to throw a wrench in the works, how about overdrive trannies? Looking at those numbers, a 700-R4 with my stock 3.55 gearing, or a 200-4R with 3.73 gears would give similar performance. The 700-R4 would have a better first gear, but the 200-4R would have better second and third. For my 400-hp 406 project, overdrive might be nice, especially since I'm pretty sure I'm going to need to do some work on the drivetrain, anyway...

    Joe

  6. #6
    Arash Sharain
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    I'm getting my stock trans rebuilt because it blew up 500 miles after I built my motor. I was going to go with a th400 but then I was told that I had to get a shorter drive shaft, different yokes, and a custom crossmember. A performance 350 should be able to handle 500 horsepower if you get a full manuel valve body and got with heavy duty componants, a 2.75 first gear with be nice also.

  7. #7
    MaineShark's Avatar
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    Originally posted by Arash Sharain
    I was going to go with a th400 but then I was told that I had to get a shorter drive shaft, different yokes, and a custom crossmember.
    What year is your 'Vette? The TH400 was offered in many C3's, so it should be a bolt-in thing (well, with the appropriate parts from a C3 that originally had a TH400).

    I think the crossmember was changed in '80, though, so that might pose a problem.

    Joe

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    Are the TH350/400 both for automatic and manual transmissions? Because aren't they (auto and manual) different weights and suspended differently (auto with welding and manual with bolts?)?

  9. #9
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    The TH350 and TH400 are both auto transmissions.

    The auto and manual transmissions are both bolted to the crossmember. The auto crossmember is then bolted to the frame, while the manual crossmember is welded to the frame.

    Joe

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    Oops, I had it backwards. Thanks for clearing that up, Joe!!

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