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th 400 or 700r4

Discussion in 'The Garage' started by AllamericanK5, Feb 4, 2006.

  1. AllamericanK5

    AllamericanK5 1/2 ton status

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    i just rebuilt a th400 and my 203 tcase decided that it was going to take a crap soo i thought i would rebuild it and its gona cost around 400 for the kit dont wana spend that sooo i have a 208 that was bolted to a 700r4 the housing on the trani was cracked soo i went to a th400 and 203 combo i had laying around wut im getting at should i try to find another 203 that will bolt up the the 400 or should i get a R4 and use that im more of a weekend wheeler and it is my DD i like doing trials like carnage here in colorado will it be heavy duty enough for that or should i stick with the th4oo
     
  2. muddybuddy

    muddybuddy 3/4 ton status

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    find a 205 for the 400, thats what id do
     
  3. big83chevy4x4

    big83chevy4x4 3/4 ton status

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    if you put anything other than a np203 behind your th400, you will have to tear it down and swap the output shaft, they are different lengths.

    there are a couple ways you can go, get a np203 from a th350 (dime a dozen) pull the range box off both and swap the th400 input into the th350, or if the range box is good, just swap that.

    or

    if your range box is good, find a np205 and have the input swapped to a 31 or 32 spline and go with a doubler.

    im guessing that your np203 was converted to part time and either that wore out, or it wasn't run in 4wd enough and didn't pump any oil and killed it that way, but this is all speculation.

    the 700r4 should be strong enough if it was rebuilt with the needed upgrades and your not to hard on it and your gearing/tires are proper for your truck.
     
  4. AllamericanK5

    AllamericanK5 1/2 ton status

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    i have 456s 35s for now and my 203 was convered but it was the chain that started to rub on the case and i got in there and theres sum trush washers that need replacing soo i thats why i was going to rebuild
     
  5. 85-m1028

    85-m1028 1/2 ton status

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    sound like a 700r4 will be a little better for a dd gas milage wise, Id go for that and the lower first gear!!
     
  6. Hossbaby50

    Hossbaby50 3/4 ton status

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    Swapping in a 700R4 inplace of a th400 is a downgrade. The 700R4 is alot weaker and alot more expensive to rebuild when you break it. I have a 700R4 in my K5 and I have a th400 waiting for it to die so I can upgrade to the stronger th400 tranny.

    Harley
     
  7. jscurtiss

    jscurtiss Newbie

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    Isn't a 88-91ish 700r4 pretty stout, or can't you just get it built -- then have the OD?
     
  8. Leper

    Leper 1/2 ton status

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    Not as strong as a 400. OD is nice, but if you don't do alot of highway driving, why have it. Getting a 700 built to last like a 400 will run around 2 grand by most companies websites. There are many more heat issues with a 700. I only put mine in OD if I am going over 60 on flat ground.
     
  9. gmcman355

    gmcman355 Registered Member

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    if you aren't wheeling hard and the rig is a dd go with the 700. put a big cooler on it and make sure the lock up is working. my 90 k1500 has a 350 with t/b spacer and injector spacer 700 trans and 10bolt rear ifs frt. with 9 in lift 37 mtrs and 5.13 gears i can get 14 mpg on the highway and with the low first gear off road is great
     
  10. 6.2Blazer

    6.2Blazer 1/2 ton status

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    I won't argue that the TH400 is the stronger tranny, but you would have to beat on a properly built (or even a stock later model) 700r4 to get it to die.

    The biggest advantage the 700r4 and 208 have is a lot lower gear ratio.......with 4.10 axle gears you are talking around 32:1 vs. only around 20:1 with the TH400 and either the 203 or 205.

    The 700r4 also has the OD 4th gear which can be real nice if you are driving on the street.....let's you have a lot lower axle gears and still a nice cruising rpm on the highway.

    But again, it's really hard to beat the brute strength of the TH400.
     
  11. 1985_K5_Silverado

    1985_K5_Silverado 1/2 ton status

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    A place like Bowtie Overdrives can set you up with a beefed K-case "level 2" 700R4 for about $1,200 (bring your own converter for that price, and allow for shipping costs).

    This really doesn't ave much to do with the topic, but I think that the real pitfall of the 700R4 is probably that a disturbingly high percentage of folks that work on their own vehicles can't seem to wrap their heads around the idea of the importance and necessity of TV cable adjustment on these trannies. No matter how many tines they are told in bold capital letters not to drive the vehicle with an improperly adjusted TV cable, they sometimes do it anyway ("...but, that's just a kickdown cable - isn't it? No, I was gonna read that later...next week...or maybe never...").

    It might be helpful to some to see a pressure test table of acceptable values at different TV openings for the 700R4 (out of the GM shop manual perhaps), in order to help out their understanding part of what the TV cable does.

    In some ways, it's a lot like the fiber optics used in the early C3 Vettes; even some body shops didn't get the optical thing, and would even try soldering the fiber optic lines during collision repair, as if they were electrical wires!

    Some folks don't need nor even want overdrive. Overdrive is great if you need it (or just want it) for higher-speed road use, to boost mileage or reduce noise on the highway or whatever. That's up to you. I like it for the highway.

    If you need beefier OD trans than a beefed 700R4, but still need OD, there's always the 4L80E, but bring a thicker wallet for that brute.
     
  12. HarryH3

    HarryH3 1 ton status Author

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    I've got a 400/205 combo now and plan to swap to a 700R4/208 or 241 combo. It gets me fairly close to the low range of a 400/203/205 doubler combo, plus gets better mileage on the road.
     

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