1. Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.
    Dismiss Notice

Transmission And Transfer Case Swap Ideas

Discussion in 'Early CJ5 and CJ6 Tech' started by garage gnome, Sep 6, 2020.

  1. Sep 6, 2020
    garage gnome

    garage gnome ECJ5 welder

    Western MA
    Joined:
    Jun 19, 2009
    Messages:
    3,083
    In the future, I want to swap the T14 out of Snowshoe for a 4 speed. I saved a T18 out of a Ford truck just for this, but reading into putting it behind the 225 is some work. The bearing retainer has to be machined down and holes drilled and and so on. Plus I would have to buy an adapter for the Dana 18 anyways. So my other thought was to use an SM420 since I have about 6 of those. Then it would bolt right up to the v6. I know people run into a front driveshaft clearance issue with the big bulge for the reverse gear on the passenger side. Then I looked into the adapter for the D18 to an SM420 and it seems quite long. I looked at a Dana 300 and those can be clocked and the adapter is shorter. Of course, I would then have to swap out the rear axle for a centered 44, which isn't a big deal since I have two in stock with 3.73s and an ARB air locker for one. :D

    So would an SM420 and Dana 300 be the best combo? Would clocking the 300 solve the clearance issue? I'm open to ideas. I also have some SM465s hidden away too... :ninja: I like the lower 1st of the SM420 though. I kinda wanted to keep this jeep as an old school wheeler with a powerlock in the rear with a ff kit and the stock D27 with a limited slip in the front. The plan was a low range kit in the transfer case, so the SM420 and Dana 300 with a 4:1 kit would get me to 104:1 crawl ratio.
     
  2. Sep 6, 2020
    jzeber

    jzeber Well-Known Member 2022 Sponsor

    Morgan Hill, Ca
    Joined:
    Nov 15, 2003
    Messages:
    3,322
    Will the 300 fit in there? I don't remember seeing this done before but my memory isn't what it used to be either.
     
  3. Sep 7, 2020
    sdcj6

    sdcj6 Sponsor

    San Diego
    Joined:
    Sep 25, 2002
    Messages:
    366
    When I had a SM420 in my Jeep Tom Woods driveshafts made a special u joint at the transfercase that used a standard size joint and and was small enough to clear the transmission. This was quite awhile ago and he used my Jeep for the proto type. He said he was going to list it in his catalog but he never did. I think if you called him he would remember it and would know how to make one for you. I think the SM420 is one of the best available for a CJ.
     
  4. Sep 7, 2020
    garage gnome

    garage gnome ECJ5 welder

    Western MA
    Joined:
    Jun 19, 2009
    Messages:
    3,083
    It doesn't seem much bigger than a dana 20.
     
  5. Sep 7, 2020
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
    Joined:
    Aug 13, 2015
    Messages:
    6,656
    The 300 has the same dimensions between the gear shafts as the 18 and 20, but most models are a little longer than the 20. I remember there being one single year of the Jeep 300 that had a shorter rear output that got it in the realm of the length of the 20, but I’d have to research it to remember specifics.

    I have both (20 & 300) here if you need any measurements.
     
    garage gnome likes this.
  6. Sep 7, 2020
    garage gnome

    garage gnome ECJ5 welder

    Western MA
    Joined:
    Jun 19, 2009
    Messages:
    3,083
    Yes the first year was shortest, but now Novak has a short rear output for the 300.
     
    ITLKSEZ likes this.
  7. Sep 7, 2020
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
    Joined:
    Jul 30, 2003
    Messages:
    8,513
    Find a Scout 300 with the Texas pattern.
     
  8. Sep 7, 2020
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
    Joined:
    Aug 10, 2003
    Messages:
    23,596
    IIRC the first year or two the 300 was offered had the short output. After that they went to a slip-yoke output (?) which is longer.

    Just me - I would go with the T-18 and stay with the Dana 18. No experience, but I understand the T-18 is a better shifter than either of the Muncies. Maybe Chuck or others with experience could comment. Supposedly the Ford case is easy to adapt to the GM bell - Novak has a page about it. Certainly should not be a barrier to someone with the resources that Nate has.

    The Novak Guide to the Adapting Ford Style Transmissions to GM Engines

    Plus the T-18 conversion is possible with 100% junkyard parts.
     
    Last edited: Sep 7, 2020
    RATTYFLATTY likes this.
  9. Sep 7, 2020
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
    Joined:
    Aug 13, 2015
    Messages:
    6,656
    No, it’s still a standard yoke. The configuration of the speedometer drive is just different and caused a longer output.
     
  10. Sep 7, 2020
    Rich M.

    Rich M. Shoe salesman 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Maryland
    Joined:
    Mar 23, 2008
    Messages:
    2,169
    T18 easy to adapt but its a slow shifter and missing a gear will buy you double clutching. Still it's in my rig. I have a BOP scattershield with the AA adapter bolted to it I'd part with. It requires an extended pilot bushing due to adapter thickness. The adapter replaces the bearing retainer.
    The NP435 is a sweet shifter with a comparable first. If I had to do it over...
     
  11. Sep 7, 2020
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
    Messages:
    12,529
    ‘80-‘83 CJ-5 got the short rear output as did the CJ-7 with I-6 and Automatic transmission.
    Easy way to tell is if the speedo driven housing threads in like an 18 or 20 it is a short shaft. If held in place by a retainer like a 231, 241, 208, etc. it is a long shaft.
    If you clock a 300 down to clear the transmission bulge on the 420 you most likely will lose ground clearance. Just something to consider.
    Parts for T-18’s and SM-465’s are pretty readily available. Less so for the 420. 465 is the largest of the 3 four speeds you mentioned. Parts for Dana 300’s are getting harder to find unless you want to spend money on upgrades. Price them out before making your decision.
    Using the Dana 18 will let you use existing rear axle, transfer case, and keep decent u-joint angles. Dana 20 or 300 can be challenging depending on how much lift you have and wheelbase.
    Dana 300 in stock form will net a 2.62-1 low range vs. 2.03-1 of a 20 (in stock form) and 2.46-1 of a 29 tooth input 18.

    there is much, much more but these are some high points to consider.
     
    garage gnome likes this.
  12. Sep 7, 2020
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
    Messages:
    12,529
    Yes. The long output shaft has the speedometer drive gear cut into the shaft. The short version used a removable drive gear like a 20 or 18.
    The long shaft versions are known to be slightly weaker but in most applications work just fine. Upgrades are available.
     
  13. Sep 8, 2020
    4S50

    4S50 I’m back!

    Idaho
    Joined:
    Sep 30, 2002
    Messages:
    123
    I put an SM465 behind my 225 with the Novak 1” adapter to the Dana 18 and it works great. Really short, stout, combo.
     
  14. Sep 8, 2020
    RATTYFLATTY

    RATTYFLATTY I think you need a little more throttle

    Central MN
    Joined:
    Oct 23, 2007
    Messages:
    515
    My vote is for the T-18, as timgr said it can be done with junkyard parts. I have done this swap with these socalled junkyard parts. If you casn't locat the trany to t-case adapter they are avalible in the aftermarket world. On the machining side of things all I had done was to make the T-18 input bearing retainer external dimentions match the of the donor(T-14/86). With this done drilling and tapping the bellhousing is a pretty simple process with no adapter needed but you do need the standard bell not the long one from a 71 CJ, if you are sourcing from the Jeep world. I picked up a pilot bearing from Novak.
     
New Posts