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Muncie swap

Discussion in 'Chevy Trucks' started by jlsanborn, Sep 18, 2003.

  1. jlsanborn

    jlsanborn Member
    Messages: 34

    My K30 has the Muncie 4 speed married to a NP205 t-case. The trans is a whiny unit that absolutely refuses to stay in third when wound up hard. The shifter has alot of slop when in gear. I have done the clutch and motor/trans mounts.
    My local bone yard contains a few 2WD pickups with the same transmissions (i think) for $50.
    Are the 1/2, 3/4 and one ton gearboxes the same?
    Can the 2WD trans be married to my NP205?
  2. reallyrusty

    reallyrusty Member
    Messages: 71

    If you are talking about the sm465 the answer is yes as long as it has the same type output spline (different years had different splines). The adapter that you currently have between the transmission and transfer case should bolt on in place of the tail housing that is on the two wheel drive transmission. hope this helps
  3. wyldman

    wyldman Member
    Messages: 3,265

    reallyrusty is correct.I believe yours should be a 10 spline output shaft.
  4. jlsanborn

    jlsanborn Member
    Messages: 34

    Any red flags I should be looking for when scrounging for used gearboxes?
  5. EZSnow

    EZSnow Senior Member
    Messages: 205

    you should have no trouble finding an SM420/ SM465. I think chevy started using them around '48 and used them as long as there were 4-speeds available in their trucks. Is it a spicer instead of municie? When I think muncie, I think M20, M21, or the big daddy, M22 rockcrusher (tim allen grunt) Anyway, I think the only external difference between a 420 and 465 is either the output, input, or maybe both spline counts. 4wheel and offroad has done a few articles on them. I have a 420 in a 1952 chevy 2-ton flatbed. Someday I'll fill it with a late diesel.:cool:
  6. reallyrusty

    reallyrusty Member
    Messages: 71

    The sm465 is a muncie used from about 68 to 91ish in up to 2 ton applications. It is a heavier version of the 420. I don't believe you can bolt a 420 in using your adapter, though i;m not positive. It is tough to tell positively if the gearbox is any good without running it. I would look for overall appearance (has it been under water for 3 years) do the input/out shafts turn freely. Does it feel ok when you shift it. Other than that you'll have to run it. If you have to rebuild it you can get all the parts for about $110 if you want to do it yourself. hope this helps