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Dana 20 Swap Reality Check

Discussion in 'Early CJ5 and CJ6 Tech' started by kenb, Mar 22, 2023.

  1. Mar 22, 2023
    kenb

    kenb Cleverly disguised as a responsible adult

    Detroit
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    My 68 has a lot of leaks from the transfer case and is a bit noisy. I suspect it will be due for an overhaul soon. It's a single stick Dana 18 with a T14, axles are Dana 27 and a tapered 44 in 3.73 with 10" drums. My wheels won't accommodate 11" drums.

    I may have a line on a Dana 20 with the appropriate bull gear for the T14. I was thinking it might make sense to swap to that over a rebuild of the 18. What I'm wondering about is the complexities of such a conversation and how many other things I would need to change.

    Obviously I would need to source a rear axle with a center differential. I take it I would be looking for a '72 and up CJ axle. How common is 3.73 for a ratio on these? Can I move the 10" brakes over to such an axle? Is the width of the axle the same?

    The other thing I wonder about is the driveshafts. Does such a swap generally result in needing different length driveshafts?

    Are there any other potential pitfalls i should consider?
     
  2. Mar 22, 2023
    Buildflycrash

    Buildflycrash More or Less in Line. 2024 Sponsor 2022 Sponsor

    Gulf Breeze FL...
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    The TC rebuild isn’t all that hard. I even did one myself this winter. Axle swap is easy enough but the cost and time and cost of new driveshaft, swapping brakes. You’re going to project creep yourself into many hours of work.
     
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  3. Mar 22, 2023
    colojeepguy

    colojeepguy Colorado Springs

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    You'd be losing a significant amount of low range gear ratio, if that's a concern to you.
     
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  4. Mar 22, 2023
    Twin2

    Twin2 not him 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    rebuild the 18
     
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  5. Mar 22, 2023
    Wmi68CJ5

    Wmi68CJ5 Let the Sun Shine!

    Twin Lake MI
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    Source an 18 rebuild it on the bench and then swap it for yours. Very little down time. IMHO the hardest part on the rebuild is setting end play on the rear output but that is just varying a few shims at most. Everything else is pretty straight forward
     
  6. Mar 22, 2023
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Maybe if you can give more of the motivation to why you are interested in the swap, you might get more specifics to your question. Basically, I think most of us interpret that you want to do the swap specifically to avoid a rebuild of the D18 - and I think that is why most of the responses are suggesting staying with the D18. In other words, a rebuild is much less hassle than than dealing with the swap and axle and brakes etc. But, if there are other reasons you might be going the D20 that justify some of the hassle, then basically, you've already mentioned the swap issues.....The D20 has some advantage of being a 'through-drive' so its much nicer sounding in 2wd high when cruising. The intermediate centered D44 is stronger (flanged)....but you give up some low range in the D20. I don't think you would need different driveshafts, as the D20 case and location should essentially be identical to the D18. The front output should be the same, and although the rear output shifts to the center, with a centered rear diff, the distance should be the same. 10" brakes should swap over - or you could swap the D27 front brakes to 11" and have much improvement.
     
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  7. Mar 22, 2023
    duffer

    duffer Rodent Power

    Bozeman, MT
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    Maybe but the high output of the D20 with its steeper driveshaft angle does require a longer driveshaft and whether or not there is enough length in the splines to take up the difference is open to question. Personally, like others, I would stick with the D18. Yep, more noise and arguably a little more maintenance but with the lower outputs and the fact that they are in line with each other, it definitely works better on the trail, not to mention the 2.46:1 low range versus 2.0:1 for the D20 for the stock gearing. Sticking with the D18 is probably also a couple of magnitudes less work.

    You should be able to find another D18 pretty cheap. Around here, they are pretty much worth 7 cents a lb at the scrap yard. Is this the V6/large index case?
     
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  8. Mar 22, 2023
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Two more issues with swapping in a Dana 20 that haven't been mentioned:
    1. Cutting up floorboards and figuring out a boot for the shifter since it's in a different location.
    2. Figuring out a new parking brake. A centered D44 will come with parking brakes in the 11" drums but you will need to rework all the cabling under the Jeep. If you swap to 10" brakes you loose the possibility of parking brakes on the axle.
     
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  9. Mar 22, 2023
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Good point....how much higher is the D20 rear output...1-2"? It's basically where the 18 pto is. Also, the D18 allows for an easy OD whereas the D20 is much more challenging to get an OD....
     
  10. Mar 22, 2023
    duffer

    duffer Rodent Power

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    The difference is close to 3".
     
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  11. Mar 22, 2023
    duffer

    duffer Rodent Power

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    And we shouldn't mention the function of the D20 shifter. Engineering design by R. Goldberg----
     
  12. Mar 22, 2023
    Rich M.

    Rich M. Shoe salesman 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    At this point the youngest D20 is over 40 years old and will need going through as well. I'm with the source an 18, rebuild it then swap out.
     
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  13. Mar 22, 2023
    kenb

    kenb Cleverly disguised as a responsible adult

    Detroit
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    Thanks for the replies. My motivation wasn't to avoid a rebuild, I have rebuilt them before and I have a good spare on hand for parts. I was just thinking it might be worthwhile for the quieter performance on the highway since highway driving is the majority of what I do with this Jeep. It sounds like the additional parts and labor would make this not worthwhile. I also don't want to lose any low range since the axles are 3.73. I'll plan to just rebuild the 18 with a good Novak kit when it becomes necessary.
     
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  14. Mar 22, 2023
    47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

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    I replaced my D18 with a car for better highway performance. No fabrication at all, direct swap in.
     
  15. Mar 22, 2023
    kenb

    kenb Cleverly disguised as a responsible adult

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    Point taken. I try to drive the Jeep as much as practical so it doesn't just sit all the time. Around here that means driving 55
     
  16. Mar 22, 2023
    garage gnome

    garage gnome ECJ5 welder

    Western MA
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    With a D20, you'll loose the ability to have an overdrive, which is a big loss in my opinion.
     
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  17. Apr 3, 2023
    fhoehle

    fhoehle Sponsor

    Harford Township, PA
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    I rebuilt my Dana 18 and also installed the AA tapered bearing kit. Was considerably quieter on the highway although louder than any Dana 20. I did eventually swap out for a Dana 20 because we were driving long distance and towing a 17' camper constantly. I also built a Dana 60 centered rear at the same time. I would probably just stick with the Dana 18 though in your case. I certainly recommend the tapered bearing setup.
     
  18. Apr 4, 2023
    colojeepguy

    colojeepguy Colorado Springs

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    Rebuilt my D18 with the tapered bearing setup....it lasted maybe 20k miles and the bearings were toast. I went back to a regular setup.
    YMMV
     
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  19. Apr 4, 2023
    Twin2

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    our jeeps make noise driving down road
    maybe time to have my hearing checked :D again
     
  20. Apr 4, 2023
    kenb

    kenb Cleverly disguised as a responsible adult

    Detroit
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    You must put some serious miles on your Jeep
     
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