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700r4 cracking.

Discussion in 'Automatic Transmission' started by Logan Sigvaldason, Jun 11, 2019 at 8:05 PM.

  1. Logan Sigvaldason

    Logan Sigvaldason Junior Member

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    Location:
    Arborg, Manitoba, Canada.
    First Name:
    Logan
    Truck Year:
    1985
    Truck Model:
    C10
    Engine Size:
    385
    So my 700r4 tranny has cracked twice now. Once on the passenger side of the bell housing, which I got welded up due to lack of funds. Then shortly after the tail housing split off and dumped all the oil on the highway.

    Pretty certain the tranny is pooched now but I looking for what's causing this. I had a vibration, I checked it out before and the tail broke off and seen my yoke on my rear diff was a little worn so I replaced it but the next day it happened. I'm trying to figure out why.

    Best idea I have as to why is maybe my driveline angle is fucked, this truck originally had a th400 with a two piece shaft and a 10 bolt rear but I have basically changed everything on it.

    I built a 385 stroker motor for it putting about 450 horse out. As well I have put in a th350, and a 700r4 in it and changed the rear end to a posi 12 bolt.

    What I am thinking maybe is that 12 bolt was out of a 4x4 and I have a 2wd so maybe the diff sits at a different angle or something of the sort.

    If anyone has ideas as to why this is happening would be much appreciated. Thanks.
     
  2. Bennyt

    Bennyt Junior Member

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    I can think of a few reasons your trans cracked: driveshaft out of balance, too long, etc. Have you checked the angles to make sure they are within range? You can correct with wedges. Is it a CV shaft? 2wd vs 4wd axle not going to be the problem.
     
    Last edited: Jun 11, 2019 at 11:22 PM
  3. Matt69olds

    Matt69olds Full Access Member

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    Are there suppose to be any braces between the engine and transfer case?
     
  4. idahovette

    idahovette Full Access Member

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    # 1 post C10?
     
  5. Logan Sigvaldason

    Logan Sigvaldason Junior Member

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    Logan
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    Engine Size:
    385
    It's a 2wd no transfer case
     
  6. Bennyt

    Bennyt Junior Member

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    Engine Size:
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    Why did you go from a 2 piece shaft to 1 piece?

    How did you determine the correct length? I have seen lots of housings break when the shaft is too long and the suspension compresses and the slip yoke bottoms out in the trans.

    Is it a Long Bed and supposed to have a carrier bearing?

    Was the shaft balanced?

    I've seen some blocks that had the bellhousing mounting out of square to the crank centerline which didn't cause an issue with glides and 3 speed manuals and then when an overdrive is added the angles are greater due to the overall increase in length.
     

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