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Thread: nailhead tranny swap

  1. #1

    Post

    Is there any more recent trannys that will bolt in, and by that I mean have the same bell houseing abd bolt to my flexplate, on my 1960 electra, w/ 401 nailhead.
    I am concerned that swapping in something else might not be able to handle the power.
    I also know that I have to put a diffirent rear axle on it, since I won't be using that darn torque tube anymore, and I want an external driveshaft anyway.

  2. #2
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    Bendsten`s Transmissions in Minnesota has adapter plates that will let you put any GM tranny behind that 401. That is the easy part---the opening up of your driveline is the tough job. Good Luck!!!! [img]graemlins/thumbsup.gif[/img] [img]graemlins/thumbsup.gif[/img] [img]graemlins/thumbsup.gif[/img]

  3. #3
    sergio Guest

    Post

    Northwest Speed Equipment from Lake Oswego, OR has the same adapters for a much better price. Ask for Marty at 503.697.0500. He is incredibly knowledgeable about Nailheads.

  4. #4

    Post

    ok, I came across a 65 th400 out of a gs.
    The bellhousing is the same bolt pattern.
    I know that I need a gs starter, but I am concerned about the flexplate. Apparently the 65 flexplate will not bolt to the crankshaft, via diffirent bolt pattern.
    Would I be able to use the stock 60 flexplate with the 65 starter?

    Chris

  5. #5

    Post

    Chris,

    It is the crank and flexplate of 401/425s that are not the same before 64. The earlier engines had a larger crank flange, larger pilot hole, a triangular flexplate with a larger mounting diameter and the ring gear for the starter was on the transmission converter. 401/425s after 64, had a smaller crank flange, smaller pilot hole, a round flexplate with a smaller mounting diameter and the ring gear was on the flexplate. The bolt holes for both flexplates are the same, but the mounting diameters of the flexplates are not the same. You could (1) swap a later crank in into the earlier engine (using the earlier mains) or (2) open up the diameter of a later (round) flexplate to fit the earlier crank flange and add a bushing to reduce the size of the pilot hole.

    The 6 bolts for the flexplates are symmetrical. They will bolt on 6 ways, but are only right when the index hole in the crank lines up with the hole drilled through the flexplate.

    Lastly, if you got the transmission from a GS Skylark, they were equipped with a two speed ST 300, not the three speed ST 400. They are a good trans, but will not give you any real advantage over a dynaflow.
    Steve B.



    67 GS 525 Buick Stage IV
    66 GS Convertible
    65 GS HT
    63 Riv
    02 Subaru WRX Turbo
    03 Ford Cobra Convertible (Factory Supercharged)

  6. #6

    Post

    allright! Thanks, at least I know not to get that tranny.
    I guess I just get a later flexplate and drill it out.
    NW equip says they can get me a buching for 25 bucks, so I am thrilled, and on the prowl for parts.

    Chris

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