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sm420 stuff

Discussion in '40- & 55-Series Tech' started by tennfj40, Jan 9, 2003.

  1. tennfj40

    tennfj40

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    I know I am bugging everyone with questions today, but was also considering sm420 conversion, was looking at tech section and saw the install, do you not have to change the ouput shaft on the sm420 so it will mate with the4 speed tc, or is that $200 adapter plate kit all I need?
     
  2. woody

    woody Internet Fireman Staff Member

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    the SM420 output is 10 spline and matches the 73-older t-cases. AFAIK, there is NO adapter from the SM420 to the fine-spline 74-newer t-cases. (AA might have one, but it would be a LONG adapter and not just the plate)

    The 73-older t-cases are 16% lower in the low range and still 1:1, so you do get a bit better crawl.

    IMO, finding a 73-older t-case will be cheaper than replacing a mainshaft in the SM420 (if one is even available) and likely cheaper than the AA stuff (if that's even available)

    (am I even here today....d'oh!!)
     
  3. Mace

    Mace rock scientist.. Staff Member s-Moderator

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    AA does make the adapter but it is like $400
    Find a plate and case (sell the 4 speed to finance the new case.. )

    Or get a really old case (the brittle ones) for next to nothing because no one wants them, and stuff the gears in to the 4 speed case :)
    Much stronger..
    Oh yeah, then get a plate adapter ;)
     
  4. Planet_X

    Planet_X

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    sm-420 mated to 4-speed transfer case w/plate style adapter. Key 10spline input gear w/4-speed teeth count.

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