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th350 to th400

Discussion in 'Chevy Trucks' started by bodhidexter, Oct 23, 2004.

  1. bodhidexter

    bodhidexter Junior Member
    from ma
    Messages: 11

    I have done a search on this and can't find a answer directly on point, can a th400 be swaped in place of a th350 on a 1979 c10 my main concern is drivshaft lenth. Also tourq converter. I'm sure the bolt patterns are the same(?) and i am aware of differences in detent.
  2. 572bowtie

    572bowtie Member
    Messages: 44

    iam pretty sure you can just bolt them right up the driveshaft should be the same length and the detent cable will be the same as well b/c i have a 79 1/2 ton k-10 and i want to do the same thing to mine.
  3. 572bowtie

    572bowtie Member
    Messages: 44

    the torque converter you would want to use the same one that comes with the tranny you should never use a nother tq from a diffrent tranny. My first post that i put in here is wrong i want to put a 400 in and get rid of my 350 b/c i think that the 400 are tougher for off-road. Also those cast-iron transfer cases weight about 350 lbs.
  4. WW LawnCare

    WW LawnCare Junior Member
    Messages: 5

    Yes and no the turbo400 use an electronic kickdown so you must get the switch to make the kickdown work switch is mounted at the gas pedal. The th400 is shorter than the th350 so the driveshaft must be altered and you tranny mount might have to change also. You will need to get a tourqe converter for the th400. Also while doing the swap you will probably need to change some other things than what I have listed because there is no such thing as an easy conversion. My sugestion is to find a good builder of the th350 and keep it or find a truck with the th400. Good Luck Jerod
  5. wfd44

    wfd44 Senior Member
    from Maine
    Messages: 369

    :dizzy: Is this thing 2wd or 4wd?

    If it is 2wd why bother unless you are builing a nasty street/drag truck. You may need to shorten (or even lengthen) the drive shaft (not a big deal most any competent automotive machinist can do it). There are multiple lenths of tailshaft on TH 350's and I belive only one on a 2wd TH400. As mentioned elsewhere (especially if a mild street 2wd) get a good built up 350 and run it.

    If it is 4wd you will need a different trans-transfer adapter for the 400.

    Key differences:

    TH400 is a little beefier internally
    TH00 has electric kickdown
    TH350 has cable kickdown
    TH 400 main case is longer
    Bellhousing bolt patterns are the same (Chev, BOP, or combo)

    Also remember the number one killer of automatic transmissions is heat. Run coolers and keep the fluid cool and clean.
  6. bodhidexter

    bodhidexter Junior Member
    from ma
    Messages: 11

    follow up

    as to question as to 2 or 4 wheel drive,i stated it is a c-10 i.e. 2 wheel drive not k-10(4 wheel drive)I am building this with a 427 tall deck truck engine (might even go nitros)for street /strip,but not a every day driver.