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th350 behind 6.2

Discussion in '1982-Present GM Diesel' started by thedrip, Nov 21, 2006.

  1. thedrip

    thedrip 1/2 ton status

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    I know it was never done factory. There were th350's behind the bastardized olds 5.7L diesel. Besides the governor, torque converter, and making a kickdown cable bracket, does anyone see a problem with this? I understand longevity won't be the greatest, but I have a 350/203 and a 6.2, and I have a very very tired 350 gasser and a broken case th400/np208. This sure makes a good 6.2 + good th350 seem like a bright idea to me.
     
  2. savagek5diesel

    savagek5diesel 1/2 ton status

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    i've asked a few questions in this forum on putting a 400 behind my 6.2, with no response. I know the military stuck 400's behind the 6.2's, but never heard of a 350 behind one. my one question i always asked was how to get vacum to make the tranny shift? the 400 and 350 use a vacum module, and the 700r4 doesn't. and on the 6.2 you can't plug in a vacum line in the IP. So that's the best of my knowledge, and i seriously doubt you'll get any words of encouragement using the th350 in the first place, let alone using it behind the 6.2.
     
  3. ankarback

    ankarback 1/2 ton status

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    A friend of mine has a TH350/NP203 behind a 6.2 in a Dodge W350. He says it works fine but it revs high on the highway.
     
  4. imiceman44

    imiceman44 1 ton status

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    Sorry about you not getting responses on your 400 question.
    The vacuum on a 6.2 comes from a vacuum pump, it fits in place of the distributor on a gasser.
    As for the 350, you can make it work like you said, you will need to get a low stall TC which the after market will be your only source.
    I don't think you can find a governor that will shift low unless you modify one yourself, and there you need to know what to modifiy.
    It needs more weight to open earlier, how much???
    That is trial and error.
    :D
     
  5. thedrip

    thedrip 1/2 ton status

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    Heres a good one. The 6.2 has a flexplate, originally for a th400. Will a th350 converter bolt to this flexplate? If no one knows, does anyone have a 6.2/th400 flexplate they can measure the bolt circle of the converter mounting bolts? th350 is 10.75 or 11.5, depending on the converter
     
  6. diesel4me

    diesel4me 1 ton status Premium Member

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    one way out..

    A TH350 uses the same converter as a TH400,so if your flexplate lacks the TH350 bolt pattern,you could swap in a TH400 diesel converter,which also has the desired 6 bolt pattern to the flexplate(rather than just 3 bolts like gassers) and a lower stall speed the diesel requires..

    I've seen guys run a gas tranny with only 3 bolts to the converter on a diesel,it does wind up a bit higher than a diesel converter would before it hits the stall speed,but its not really that noticeable..not sure how it would affect longevity though..

    You can use the VRV (vacuum regulator valve) and vacuum pump used to run a TH400 on a TH350 as well..I doubt the govenor shift points will be a problem,most 6.2's shift too early in my opinion anyway,and a few more RPM's before a shift wont hurt anything..

    I'd bet a TH350 will live behind a 6.2 ,as long as you dont tow heavy loads or stuff your foot in it during off road excursions..the diesel wont have enough horsepower to kill it,but what it lacks in HP,it makes up for in torque,and that is what will kill the tranny..but I know of 2 trucks with Caddy 500 motors and TH350's,and both are holding up OK under mild abuse on the street...I'd rather have a TH350 than a 700R4,as far as durability..:crazy:
     
  7. thedrip

    thedrip 1/2 ton status

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    I wasn't aware that th350 and th400 converters interchanged. If they indeed do, I have the original th400 converter out of the 6.2 donor truck.
     
  8. darkshadow

    darkshadow 1 ton status

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    i have a 6.2 that ran a 400, and still has the flexplat on if you want me to check anything
     

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