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Dana 20 With Bronco Low Gear Build Info Needed

Discussion in 'Intermediate CJ-5/6/7/8' started by mbjeeper, Mar 1, 2019.

  1. Mar 1, 2019
    mbjeeper

    mbjeeper New Member

    Moundsville, WV
    Joined:
    Apr 23, 2017
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    17
    I am in the process of rebuilding my 1975 Dana 20 CJ transfer case. I have it all apart and checked, and the bearings and seals are on order. I also have a stack of Dana 18s, assembled and disassembled..
    I have an early T shift complete Bronco transfer case that I want to use the low range out of.
    I have searched this forum and others, but I have not found a clear, correct step by step guide on how to swap the lower low range.
    I am not knowledgeable about transfer cases at all, so I'd like to follow some sort of guide or video so I can be sure to get it right.
    Is there a good guide of what exactly I need to do to do this swap? I have found a few threads with some conflicting or supposedly incorrect information, and I want to make sure that I do have the correct gears.
    Has someone done and documented this? I would really appreciate it if someone could refer me to a link!
    My 1973 DJ5 4WD, Buick 231 TH350 conversion is going well so far!
    Many thanks,
    Greg
    2MBs, 2GPWs, 1 M38, '72 CJ5, 2 XJs, DJ5 IMG_1255.jpg
     
  2. Mar 1, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    Search. The thread you want has Nickmil telling you what gear you need - it's a different PN from what's posted online. No time right now - maybe later I can help more.

    Might be cheaper to find and run a Dana 300. Same reduction ratio as the modified 20, and bolts up.
     
  3. Mar 1, 2019
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member 2021 Sponsor 2020 Sponsor

    Denver, CO
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    Jul 18, 2013
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    4,467
    I think this might be thread you are talking about Tim?
    When putting Dana 18 gears in a Dana 20

    copying the gear number from NickMils post:
    Here is a list of what is needed to make a 2.46-1 low range model 20:

    1) 18-8-23, 29 tooth 6 spline input gear
    2) 18-8-22 gear
    3) 18-8-24 gear
    4) 18-5-9 intermediate gear
    5) 18-8-37 slider gear from EARLY Bronco 20

    The rest is bolt up except you may have to grind some on the case (most do) to clear the slider gear. Sometimes you have to grind the pan rail/opening to get the intermediate gear in also depending on which assembly order you go in. I'd recommend checking it so down the road if there is a problem you don't have to disassemble the whole transfer case to get the intermediate gear out. Nickmil.
     
    Last edited: Mar 1, 2019
  4. Mar 1, 2019
    RATTYFLATTY

    RATTYFLATTY I think you need a little more throttle

    Central MN
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    Oct 23, 2007
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    488
    If you are looking at buying an adapter for the 20 to your 350 I also would strongly recommend picking up a 300 and adapting it to the 350 instead of th 20. If you have everything for the lower low 20 it would most likely offset the cost of a 300.
     
  5. Mar 1, 2019
    mbjeeper

    mbjeeper New Member

    Moundsville, WV
    Joined:
    Apr 23, 2017
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    17
    Thanks for the info. I somehow missed that thread, after a couple of months of on and off looking. Can't understand how I did that.
    I already have the adapter for the 20, several extras for parts, and my rear driveshaft is short enough. The 300 is a bit longer, which would make it worse, plus I should have all of the parts for the bronco conversion of the 20 already.
    Thank you for the proper gear numbers!! I'll be able to make sure I have everything correct now, and the grinding and clearancing (sic?)won't be a problem.
    Again, thanks
    Greg
     
  6. Mar 1, 2019
    oldtime

    oldtime oldtime

    St. Charles,...
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    Aug 14, 2006
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    3,170
    All you need / want from the early Bronco D20 is the large rear output/ sliding gear.
    That will work with any Jeep 2.46 ratio D18 gear set.
    Will not work with early 2.43 ratio D18 gear sets.
    I have a complete set of NOS Timken USA bearings for D20 if you need a set PM me...
     
  7. Mar 1, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor 2021 Sponsor 2020 Sponsor

    Medford Mass USA
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    Argh. The 300 will not bolt up unless you find the rare one from a single year of Scouts. If you could find that, it would be expensive. Never mind.
     
  8. Mar 2, 2019
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
    Joined:
    Sep 23, 2002
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    Jeep Dana 300 has a “round” bolt pattern similar to an NP 231, 241, 242, 208, etc. the low range on a 300 is 2.62-1 vs. the 2.46-1 of a low range conversion of a 20 using the Bronco “T” shift slider gear.
    20 can be converted from the stock 2.02-1 to the 2.46-1 with Bronco gear or to a 3.15-1 using Terra gears (other suppliers may still be available). 300 can be converted from the stock 2.62-1 low range to 4.0-1 low range and the outputs (front and rear) can be upgraded to 32 spline output shafts. Front requires machine work to the output housing for the larger output bearing race. The input can be modified to many different spline counts to adapt to various transmission output shafts. AA and others have conversions for this.
    The scout 300 is a rare item used only in 79 1/2 and ‘80 Scout 2’s.
    I currently have one on my workbench I’m evaluating/fixing with 32 spline outputs front and rear and a 4.0-1 low range kit in it.
    It’s desirable for the fact it can bolt directly in place Of a 6 spline input Dana 20 or 18 with no adaption.
    The one I have will be for sale by the owner. Hopefully at the Puyallup Swap Meet if I have time to finish it.
     
  9. Mar 3, 2019
    dvader

    dvader Member

    Northern Nevada
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    Jul 20, 2006
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    201
    The Dana 300 has helical cut gears which are much quieter in low range than the Dana 20's straight cut gears.
     
  10. Mar 3, 2019
    mbjeeper

    mbjeeper New Member

    Moundsville, WV
    Joined:
    Apr 23, 2017
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    I have taken the Bronco 20 apart, and I now have all of the above gears.
    I am going to use several of the gears out of the Bronco case, since it saves me from tearing apart a good 18.
    The 18-8-24 gear in the bronco case was retained by a circlip, whereas the corresponding gear on the CJ 20 was not.
    I have measured the two gears and they are identical (well, within a few thousandths).
    Will this affect anything? I don't think that it will, but I thought I'd ask.
    I am also going to modify the shift rods to get a 2 low gear. I have a twin stick set for it.
    If anyone has done this and can add anything about it, I'd really appreciate that, too.
    Thanks for the assistance! I really do appreciate it.
     
  11. Mar 3, 2019
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    No. The gear is interchangeable between the two styles of shafts.
    Before you tear down the rear output shaft/housing assembly use it to hold the Bronco slider in place and check clearance between the sliding gear (18-8-37) and the case. Sometimes only a little grinding is necessary and sometimes quite a bit. Make sure the slider can move through the whole range of movement. The pan rail on the bottom is a common clearance issue and where the case dips down in the top side for the top right mounting bolt clearance. The casting protrudes into the case. Make sure you BOLT the rear output in place when checking the clearance.
     
  12. Mar 4, 2019
    mbjeeper

    mbjeeper New Member

    Moundsville, WV
    Joined:
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    Thank you nickmil. That is good information. I will be certain to do that.
     
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