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hd th400 or th400

Discussion in 'The Garage' started by BowtieBlazer, Mar 4, 2004.

  1. BowtieBlazer

    BowtieBlazer 1/2 ton status

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    Whats the differences between the two, seems like the hd th400 was fairly common just by profiles, truck mags and e-bay. Whats the difference in the th400s?
     
  2. BlazerGuy

    BlazerGuy 3/4 ton status

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    Are you talking about the TH475? Never heard of of a HD TH400...at least not from the factory.... /forums/images/graemlins/ears.gif
     
  3. 84_Chevy_K10

    84_Chevy_K10 Banned

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    Are you talking about the thick bellhousing TH 400?
     
  4. fatboy

    fatboy 1/2 ton status

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    I might be wrong but this is what I have ran across recently>>>>>>>>>my TH400 went south so bought another one that needed a rebuild and paid a guy to do it. all is well but the shift paterns differ. It will only go into low when at very low rpm or under load.It is still doing that with a shift improver kit! I was told that it is set that way for heavy duty towing or delivery vans. To help extend that life of the transmission. I am having mine fixed with a different valve body. /forums/images/graemlins/waytogo.gif I want to shift into low while cruising at 40 MPR, just incase I need to drive over someone maken me mad>>> /forums/images/graemlins/blush.gif>>>>yes road rage>>> /forums/images/graemlins/blush.gif>>>>but that is a hole other story /forums/images/graemlins/doah.gif
     
  5. BowtieBlazer

    BowtieBlazer 1/2 ton status

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    [ QUOTE ]
    Are you talking about the TH475? Never heard of of a HD TH400...at least not from the factory.... /forums/images/graemlins/ears.gif

    [/ QUOTE ]

    well, I am pretty sure there is a plain th400 and i currently have a th400 stamped HD on the bellhousing, I thought it may have been thicker casting into the bellhousing.
     
  6. cuzinjay

    cuzinjay Registered Member

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    Just check out a transgo reprograming kit.I have one in a th400 and it will hold 1st,2nd till you shift.
    You can down shift the just the same.It has several opions for how firm/fast it shifts as well.
    Even come with extra gaskets so you and tune the shifts to you liking.
     
  7. ugly_blazer

    ugly_blazer 1/2 ton status

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    [ QUOTE ]
    [ QUOTE ]
    Are you talking about the TH475? Never heard of of a HD TH400...at least not from the factory.... /forums/images/graemlins/ears.gif

    [/ QUOTE ]

    well, I am pretty sure there is a plain th400 and i currently have a th400 stamped HD on the bellhousing, I thought it may have been thicker casting into the bellhousing.

    [/ QUOTE ]

    Well, I have searched and came up with this post that was never really answered.

    I have a TH400 from 1986 1/2 ton 2wd that I put in my K20 today. The case has "HD" on the bellhousing. I was wondering if anyone knew if the "HD" meant anything significant. /forums/images/graemlins/dunno.gif /forums/images/graemlins/ears.gif
     
  8. POWERMAD

    POWERMAD 1/2 ton status

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    Did it have a fixed or slip yoke?
    I was told by the tranny guy that rebuilt the one in my 73 that a 2wd one with a fixed yoke was a HD model.
    I have one of those in the shed.
    It came from a 3/4 ton burb behind a 454.
    Hmm now I am gonna have to go look and see.
     
  9. 84_Chevy_K10

    84_Chevy_K10 Banned

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    My 87 C/R30 has both "43" and "HD" cast into the bellhousing. The bellhousing is also thicker as would be a K case 4wd type tranny and it has bosses that are not drilled nor tapped but they're made for the thick aluminum cover that 4wd trucks often sport.
     
  10. k20

    k20 3/4 ton status

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    yeh the HD is a thicker case, thats pretty much the only difference. They also have a cast aluminum flywheel cover, instead of the thin sheet metal one on the other cases.
     
  11. ugly_blazer

    ugly_blazer 1/2 ton status

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    Mine is a slip yoke design. It had "HD" on it and "39". What I think is srange is that it came out of a 1/2 ton 2wd with a 4.3 V-6. The th400 wasn't swapped in either, I looked up a tranny filter for it and my choices were 700r4 or th400.

    Oh well, thanks for the replys, thought maybe I had somethin' cool. /forums/images/graemlins/rotfl.gif
     
  12. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If you looked it up in a parts store computer and it offered you the TH 400 or 700R4, don't use that to think your TH 400 came in that truck. It will often ask you questions that have obvious answers, and the obvious answer here is that transmission did not belong in your truck.

    The 4.3 V6 was only available in 1985 and later 1/2 ton trucks. The only possible tranny that it would have came with would be the 700R4. TH 400s were rarely available in any 1/2 ton, but they were in the 70s when they put a 454 in a 1/2 ton truck.

    No 1/2 ton truck in the '80s got a TH 400, not even the Diesel powered ones. Your 4.3L truck certainly came from the factory with a 700R4...someone just swapped that TH 400 in later on.
     
  13. R72K5

    R72K5 Banned

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    the bolted on style output shaft yoke th400's were the shorter ones in at least the 80s i know, i cant remember what the length of the th400 in the 74 C20 454 truck was.
    hmmm..
    im prety sure it was bolted on style also
    but the length, hmmm, forgot. haha

    i know that a shrty th400 2wd with blted on style yoke is same length overall with the yoke as a 2wd longtail th350 is, i happened ot be playing around with a tape measure and a couple trannies one day not that long ago, but i already knew of the 200 and 200c and 250 and 350 series trannies, (6" and 9" tails both with the th350's)

    dunno on the 475's though

    good luck
     
  14. jac6695

    jac6695 1/2 ton status

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    I have seen several 4.3 trucks with a TH400 85-86. My brother actually owned one from and it was definetely factory.
     
  15. ratzila

    ratzila 1/2 ton status

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    I've heard of the th400 were in astro vans with the 4.3 engine & 3 speed transmissions. I believe nvrenuf had one.
     
  16. 84_Chevy_K10

    84_Chevy_K10 Banned

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    If such an animal exists I will retract my statement, but I've never seen such a thing. I have seen TH 350s in 1/2 tons all the way up to 85 though, but with 305s.
     
  17. jac6695

    jac6695 1/2 ton status

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    GM didn't use the TH350 after 84 or so and knew that a carbed 4.3 would never pull overdrive in a fullsize, so the TH400 was all they had. The combination would last forever if taken care of.
     
  18. tarussell

    tarussell 1/2 ton status

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    The TH400 ( or actually a TH375 ) most certainly did come in trucks/vans/and Astro vans ordered with out an overdrive tranny from the mid eighty's to the very early ninety's .
    The great thing about these cases are that they are ALL HD casting cases . The internals are not all the same but the casting of the case is the thicker bell part ( also known as the "K" case ) - the 2WD stuff is not tapped for the dust cover with the motor mount struts but they can be tapped to the larger size bolts if needed .
    From what I have found GM used the TH375 in these applications when the TH350 went away and at some point GM just made one casting that fit all applications and the internals were application specific .
    Look at all TH400's because the TH475's are more common than just the HUGE motor homes and Chassis like that - according to tranny codes from GM the TH475's came in plenty of deisel vans / Cab Chassis / Step Vans and other Chassis ( not all had them but they are out there ) .
    HTH's , Tom
     
  19. ugly_blazer

    ugly_blazer 1/2 ton status

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    I thought that the th375 was only used for a few years, 74-76, in gm cars - caprice, electra, ets... and not since then. /forums/images/graemlins/dunno.gif
     
  20. ugly_blazer

    ugly_blazer 1/2 ton status

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    I'm pretty sure that it did. They gear indicator above the steering column was PRND21 for a 3 speed as opposed to a 4 speed. Also, as stated by jac6695, the 4.3 was carbed and I couldn't imagine it pulling the truck in overdrive with a 2.73 rear end ratio. /forums/images/graemlins/dunno.gif
     

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