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New Transmission

Discussion in 'Flat Fender Tech' started by Zup, Aug 2, 2007.

  1. Aug 2, 2007
    Zup

    Zup New Member

    Joliet
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    May 27, 2007
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    38
    My t-14 just broke and I'm wondering what transmission would be a better conversion the t18 or sm420. I think they're both great trannys but which one is better as far as adapting to bellhousings and moving cross members and lengthing drive trains etc. Thanks.
     
  2. Aug 3, 2007
    lynn

    lynn Time machine / Early CJ5 HR Rep Staff Member Sponsor

    Huntingdon PA
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    Sep 20, 2002
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    You will need to move crossmembers and lengthen front/shorten rear DS with either set up.

    The T18 swap is what I used (Jeep T18 from a full size). It required an input shaft swap to the Ford 6.5" length, and a swap to a pre-'71 225 bellhousing, and an AA adapter #712528
    However, the rear adapter for the D18 was already on the trans, the factory Jeep T18 to D20 adapter. Also needed a main drive gear. The T14 trans mount works with this set up; mine needed 5 minutes with a round file to match the holes in the T18/D18 adapter.

    It's my understanding that the SM420 bolts to the ECJ5 bell with fewer problems... but then the D18 adapter is pretty expensive...

    As they say, 6 of one, half dozen of the other...

    Either tranny will make a world of difference offroad compared to the T14... either swap is well worth whatever it costs to make it work! :)
     
  3. Aug 3, 2007
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ Sponsor

    Oklahoma City, USA
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  4. Aug 3, 2007
    trickpatrick

    trickpatrick Done? LOL

    North Idaho USA
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    Nov 29, 2006
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    838
    The sm 420 seems simpler and like you said is a great trans.

    It will bolt right up to 225 bell.


    Need tcase adaptor. which is extra 4 inchs.
     
  5. Aug 3, 2007
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ Sponsor

    Oklahoma City, USA
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    The T-18 bolts up with very little modification.

    Even with the adapter, it is only 2.5" longer than a comparable T-18 setup. I thought McRuff said onetime that someone was making a 1" adapter for the SM420.
     
  6. Aug 3, 2007
    jd7

    jd7 Sponsor Sponsor

    Nacogdoches,Texas
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    that would be good short setup then....
     
  7. Aug 3, 2007
    jayhawkclint

    jayhawkclint ΜΟΛΩΝ ΛΑΒΕ Sponsor

    Oklahoma City, USA
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    Yup, that's the point I was making. Sorry if not clear enough. I do remember reading once that McRuff posted the SM420 with xxxxxx adapter was the shortest truck 4spd drivetrain available for the CJ. Can't find it now.
     
  8. Aug 3, 2007
    Warloch

    Warloch Did you say Flattie??? Staff Member Sponsor

    Falcon, CO
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    Mar 4, 2003
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    Between the 420 and 465 it's the 465 with the Novak 1" adaptor. When I did my lookin I measured from the BH mount to the front of the Tcase (so that any adaptors were included in the math). The T18 'can' be the shortest if you can find the right combo, then the SM465 with the 1" Novak.
     
  9. Aug 3, 2007
    Mcruff

    Mcruff Earlycj5 Machinist Sponsor

    Albertville, AL
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    Yep the sm465 is the shorter between the 420 and 465, thats the photos I posted, Its Cobys trans going in his cj3b. The sm420 would be darn near impossible to make the adapter any shorter than what it already is due to the case interference from the dana 18 to the side of the trans. The sm420 while short is very wide on the passenger side of the case. The sm465 is a tank transmission in size compared to the t18, sm420 or np435. In my area the sm420 and sm465 are easy to find and quite cheap, the t18's are there but you must find the right one, not that easy around here.
     
  10. Aug 3, 2007
    timgr

    timgr Jeepin' Nerd Sponsor 2019 Sponsor

    Medford Mass USA
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    The main advantage to the T-18 is that you can do it with junkyard parts and basic machining (drilling, tapping, some modification of the retainer IIRC). I don't think there's any way to do a SM420/465 without a commercial adapter.

    The T-15 is another possibility - it should be less trouble wrt driveshafts, crossmember, floor pans, etc.
     

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