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TH400 or TH350 for doubler?

Discussion in 'The Garage' started by k5-newbie, Apr 18, 2005.

  1. k5-newbie

    k5-newbie 1/2 ton status

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    I have a turbo 400 with a 205 in my Blazer now but I pulled a turbo 350 with a 208 out of it. Which would be better to mate to a 203 to make the doubler? Do they even make a 400 to 203 adapter?
     
  2. big_truxx

    big_truxx 1/2 ton status

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    I do in fact believe they do have 400-203 adapters. Not positive but relatively sure
     
  3. divorced

    divorced 3/4 ton status

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    Th400 and a NP203 was available from the factory. My friend had a set from a 3/4 ton truck and he sold them for $100 (trans, adapter, and t-case).
     
  4. Hossbaby50

    Hossbaby50 3/4 ton status

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    They did make a Th400/203 setup.

    A TH400 is the better way to have the doubler cause you can flog the piss out of it and not really have to worry about it. You don't have to have the TH400 to flog it though.

    Most all the guys I wheel with here in AZ run TH350 doublers and have had little problem with it. As long as the TH350 is built up some your fine. They wheel there trucks very hard and they flog the hell out of them with very good success.

    It is really up to you on what way you want to go.

    Harley
     
  5. teamgerth

    teamgerth Registered Member

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    Yes they did make a th-400/203. I have one in the garage that I would sell you the adapter and range box w/ the th-400 input for $300
     
  6. sweetk30

    sweetk30 professional hooker Premium Member

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    if easy use and built tranny 350 for the lower first gear. for all out no problems 400 setup. and if the 350 your tail shaft will need to be changed from the 208 to a 203/205 shaft. 208 was longer shaft from the tranny to tcase. easy find tho.
     
  7. big wheel bob

    big wheel bob Registered Member

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    Im interested in the adaptor, range box, and shaft. can you call me. Thanks, Bob. 910-326-2881
     
  8. Stephen

    Stephen 1/2 ton status Moderator Vendor

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    Mating to the trans one angle to look at, strength is the other.
    You can mate the 203 to the 208 adapter you have on your TH350 but the better way to go would be to change the output shaft like mentioned above.

    For the 400/203, getting all the parts in one place is the way to go, you need the output shaft for the trans, the input gear for the 203 and the adapter plate.
    Or you can use a 400/208 setup and drill the face of the 203 out to the 208 pattern.

    Experience indicates that using the Doubler makes life way easier for the trans so TH350's are typically OK. I'm running a 700R4 behind my BBC and am not sure why it's still alive other than it's almost always in at least one low gear so the trans doesn't get worked as hard all the time.

    There's some more info on mating the 203 to the trans here: ORD Doubler page
     
  9. Mudzer

    Mudzer 1/2 ton status Author

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    Go with the TH350 - you can find them anywhere ready to bolt in.

    I figure if I make a trip to Moab, I'm not going home because of some tranny problem and the requirement for having the one I have rebuilt only because they are rare to find.

    You could go to ANY junkyard - hell, probably even a Volvo yard would have a TH350 4x4 version laying around.

    I have yet to have a single problem with my stock rebuilt TH350. It's not a K case either - in fact it's a 2wd case! I have the largest B&M cooler with a fan on it and monitor my temps. I am waiting to break the case in half someday, but thats really my only worry.

    The Okie boys at WMS and Rokit Engineering run TH350s and they wheel every weekend on 44's and 49's.
     

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