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small block to big block

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by PaRedneck, Jan 13, 2003.

  1. PaRedneck

    PaRedneck Newbie

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    I am getting ready to buy an '86 fullsize Blazer and was wondering if the trannys in them would stand up to a big block 396 that is punched out to a 402? I am not sure what tranny is in it or what all they offered that year. Can't really check what is in it since I don't have it yet. Any help is appreciated. Thanks.
    Corey
     
  2. four_by_ken

    four_by_ken 1/2 ton status

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    Depends on the mileage and if it is a stock tranny or not. If someone put a 400 in there, it should be fine. 700, not unless it has been rebuilt nicely. 350, same as the 700. This is a general response, but a respinse non the less. Depends on how you drive and what the purpose of the vehicle.

    If you are going to tow or wheel with it... expect to replace/rebuild the trans.

    Ken H.
     
  3. Sandman

    Sandman 3/4 ton status Author

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    If you take it easy, anything will live. I would try it but put extra cooling on the tranny. I've got a TH350 tranny and I dont hold back with my big block. I am careful about the temperature though.
     
  4. imiceman44

    imiceman44 1 ton status

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    Well everybody assumed you are talking auto, but there is no indication here.
    But since the manuals I think would be the sm465 then it would take the abuse no problem.
    Now if it is an auto, the 400 can handle it no problem the 700 could if built correctly, and unless someone put a 350 in it you shouldn't have it in a 86.
    But if you do it can handle more than the 700 if both are stock.
    Actually the 400ci enigne option in the 70's came with a th350 not a th400 in the blazer.
     
  5. PaRedneck

    PaRedneck Newbie

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    Yes it is an automatic...sorry for not mentioning that. It already has a 4" lift on it so it is possible that the tranny could have been swapped. What is the best way to tell what tranny is in it?
     
  6. 70~K5

    70~K5 1/2 ton status

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    If it's a 3 spd does it look like texas or is it square with one corner cut off?
     

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