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Swapping A Dana 18 For A Dana 20.

Discussion in 'Early CJ5 and CJ6 Tech' started by Broylz, Feb 26, 2018.

  1. Feb 26, 2018
    Broylz

    Broylz Member

    Gallatin, TN
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    Can I take a later cj5 dana 20 and my dana 18 from behind my t14 and make a dana 20 that will fit the t14 with the 10 spline vs 6 spline variations?
     
  2. Feb 26, 2018
    Daryl

    Daryl Sponsor

    Bonney Lake, WA
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    You need to know what input gear the 20 had on it. They either had 20 degrees or 17.5 degree pitch on a 26 tooth gear. The 18-8-49 gear is the only 26 tooth gear that fits on a T-14 with it's 10 splines. It has a 17.5 degree pitch. So the 20 transfer case that you use must also be one that uses a 17.5 degree input gear.
     
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  3. Feb 26, 2018
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    '72-'75 CJ's with inline 6 and T-14 transmission used a 10 spline input model 20. Be aware your 18 with 10 spline input has 2.46-1 low range and the 20 uses a 2.03-1 low range.
     
  4. Feb 27, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Broylz likes this.
  5. Feb 27, 2018
    Keys5a

    Keys5a Sponsor

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    I've looked for this gear/number info before, but never found more than one application at a time. The page you linked is a great reference to all the variations in one place. Thanks Tim!
    -Donny
     
  6. Feb 27, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Woot! Glad I could help! :coffee:

    Likely worth cutting and pasting into your notebook. Stuff comes and goes from the internet. :shrug:
     
  7. Feb 27, 2018
    Jrobz23

    Jrobz23 Member

    Northern, WI
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    Yes, but..

    Silly question: Why? Dual offset yokes have significant advantages. Also the D44 is a great rear axle for a vehicle of our weight.
     
  8. Feb 27, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    A flanged 44 for a centered output is cheaper and more available than an offset flanged 44. JMO - if I had a Jeep with an 18 I'd spend what's needed to get the offset axle, but I have the means. I'm not so enamored to earlys though, and would probably start with a '72 or newer.

    And! I'm not so convinced that you need the flanged axle. If you feel the need, a full-floating conversion may be the sensible option.
     
  9. Feb 27, 2018
    Jrobz23

    Jrobz23 Member

    Northern, WI
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    Yeah, if I’m digging into the rear “cuz I need it”, I leaving with a full floating D44, which case the offset or not is rather irrelevant. A FF44 is well strong enough for most any set of tires we’d run at this wheel base.
     
  10. Feb 27, 2018
    Jrobz23

    Jrobz23 Member

    Northern, WI
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    I highly doubt many on this board need more strength than the stock offset 44 provides. Some do, but I bet it isn’t common.
     
  11. Feb 27, 2018
    oldtime

    oldtime oldtime

    St. Charles,...
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    Actually lots of differences between the D18 and D20 applications.

    Factory Jeep D20 has lousy reduction ratio compared to factory Jeep D18.
    D20 runs much more quitely and is the more efficient design.
    D18 keeps the differential carriers inline allowing one to better straddle trail obstacles.
    D18 allows for higher lifts than D20 due to rear propeller shaft angles.
    D18 is easy to "twin stick" if not already equipped that way..
    D20 never had a factory twin stick shifter, so its aftermarket or ho-made....
    D20 is big hole only (4" index bore)
    D18 a can be small hole (3-5/32" index bore) or large.

    I tend to consider the D20 as the better choice on the hi-way but see the D18 as a better choice for off-road use.
     
  12. Feb 27, 2018
    Jrobz23

    Jrobz23 Member

    Northern, WI
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    Semi-related. Can I machine out a small hole 18 to 4” without serious impending hassles?
     
  13. Feb 27, 2018
    oldtime

    oldtime oldtime

    St. Charles,...
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    Sure you can.... but it has to be precise.
    That said you may be better off to use a "big hole" which is a stronger case design.
     
  14. Feb 28, 2018
    Broylz

    Broylz Member

    Gallatin, TN
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    Thanks guys. My debate right now is to use wagoneer width axles or a short wheel spacer. I don't wheel much in it and it is my daily driver. I am running with 33s when turning tight. I think I am around 2.5" lift with some stupid stiff 11 leaf packs front and rear.

    My 27 front is in need of a rebuild and I have a 44 front I plan to make fit in its place. Building the front axle has caused me to debate if I want to go wider with the rear or just shorten the front a bit more. The front is a hp44 from a 78 f150 that will need shortened in either case as well as swapped driver to passenger side.

    The 20 would be the simplest swap vs something that may need a transmission swap and or adapters.
     
  15. Feb 28, 2018
    colojeepguy

    colojeepguy Colorado Springs

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    Also the 18 gives you the ability to use an overdrive which is a huge upgrade in an early CJ
     
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  16. Feb 28, 2018
    Daryl

    Daryl Sponsor

    Bonney Lake, WA
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    Almost any 20 case will work with the 18 guts.
     
  17. Mar 1, 2018
    Jrobz23

    Jrobz23 Member

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    I may end up at this route.
     
  18. Mar 1, 2018
    nickmil

    nickmil In mothballs.

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    If you are speaking strictly Jeep this is true. IH Scout 800 for about 3 years used a twinstick 20. Can be hard to find but will be a bolt on for Jeep 20. Consists of front output housing, shift rails, shifters, and assorted small parts like pivot pin, etc. the pivot pin is different from the 18. Diameter is the same but the groove for the set screw is on the opposite end of the pin. I want to say they were used in the 1968-1970 range.
     
  19. Mar 1, 2018
    oldtime

    oldtime oldtime

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    Interesting stuff.
    I sure would like to find a set up like that.
     
  20. Mar 1, 2018
    Daryl

    Daryl Sponsor

    Bonney Lake, WA
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    Herm has a few as I have sold him several of them in the last couple of years.
     
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