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TH-400 Question

Discussion in '1969-1972 K5 Blazer | Truck | Suburban' started by vtblazer, Jan 25, 2006.

  1. vtblazer

    vtblazer 1/2 ton status GMOTM Winner

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    Posted here cause it's in a 71 blazer...:crazy:

    Question is this:
    I busted the rear case of my th-400 just ahead of where it bolts to the first t-case.
    Can it be welded?
    Will it crack again at some point?

    I have a tranny shop saying "sure" but I have a mechanic saying "dont do it"

    Any other option's? :1zhelp:
     
  2. jays68yak

    jays68yak 1/2 ton status

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    I would try to find another K case th400. The K case is the 4wd case. Its thicker then the 2wd one where its mounts to the block.
    It prob could be welded but then how strong would it be?
    I would look into why it broke. Is the doubler held up with enought support?
     
  3. Greg72

    Greg72 "Might As Well..." Staff Member Super Moderator

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    Of course we all know that aluminum can be welded.

    The problem I believe it that the aluminum is now impregnated with oils and fluids from the tranny, and the odds are that you'll NEVER get the area clean enough for a complete, non-contaminated weld.

    STEP 2:

    Regardless of how you "fix" the tranny, you will want to seek out the answer to why you cracked it in the first place!! How much unsupported weight do you have behind the tranny? Usually, with Doublers people add at least one more crossmember so that the tranny and adapter don't have all that leverage against them. Also, using mounts that all have similar materials (poly or whatever) will help insure that the loads are evenly distributed too.
     
  4. vtblazer

    vtblazer 1/2 ton status GMOTM Winner

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    Called another 100 tranny shops today and finally found a guy who know's th-400's inside and out.

    He has a 'K' case that he's willing to sell too. :thumb:
    He'll be doing the internals swap over as well.

    I agree with the "DON'T" weld thing but had to ask/check.

    The tranny broke because the front driveline is to long. (no slip in the slip joint) So when I came to the bottom of that gully with both front tires hitting the far side at the same time, all the 'shock' went through the drivetrain and found a weak link, that weak link being the case.:doah:

    The doubler is supported really well, I'm sure it was the front shaft being to long.
     

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