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Bolt on Underdrive

Discussion in 'Early CJ5 and CJ6 Tech' started by O_Negative, Nov 17, 2010.

  1. Nov 17, 2010
    O_Negative

    O_Negative New Member

    Montana
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    I've been talking with a few of my "older" wheeling buddies, and they're convinced that at some time, a long time ago. There was a bolt on underdrive that would attach to the D18 the same way the overdrive does. They went on to mention that the earlier Wagoneers used a bolt on underdrive to achieve low range. I'm just trying to find some options to give me a better crawl ratio. Any info would be greatly appreciated.

    O_Negative
     
  2. Nov 17, 2010
    Vanguard

    Vanguard Take Off! Staff Member

    Vista, CA USA
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    Never heard of such a thing. You could use a Tera-low kit in the D18 to slow things down.
     
  3. Nov 17, 2010
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    The older Waggy's and pu's with the Borg-Warner Quadratrac (13-39?) transfer case (full time 4x4) had the option of low range or not. It was a bolt on unit that was an option that fitted to the back of the transfer case similar to the way the od fits on the 18. They are not interchangeable.
    Never heard of an underdrive for an 18 transfer case but anything is possible.
     
  4. Nov 17, 2010
    duffer

    duffer Rodent Power

    Bozeman, MT
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    I have been toying with the idea of bolting the low range unit from a 1339 into the 18 for years. I believe this is doable but will require machining a number of parts in addition to the adapter plate. A Warn OD drive gear can probably be reworked by someone like Liberty Gear for the input.

    The problem is the market. Such a unit would make a 4 sp T case with 1:1, 2.46:1 (or 3.15:1), 2.57:1 (from the 1339), and 6.32:1 (or 8.05:1 with TerraLows). My thought was that with such a unit, a person could run 3.07 gears and be exactly where I am at with 4.10's and the OD. This, however would not work with a 134 and might be pretty marginal with a 225 for every day use. With just about any V8, it should work great. The 1339 low range unit is a robust item and will certainly take a LOT more torque than any of the OD's.

    Mcruff????????
     
  5. Nov 17, 2010
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    I too have never seen an underdrive for the D18. I know they are available for other applications, but nothing with a D18.
     
  6. Nov 17, 2010
    O_Negative

    O_Negative New Member

    Montana
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    Feb 13, 2009
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    The main reason I'm curious about this whole venture is I'm running the 225 V6, T14, D18 and 3.73s, which is limiting my crawl ratio. I was able to pick up a SM465, that will get swapped in soon enough, once I can afford the Novak Adapter. that will get my crawl ratio around from 28 to 1, to 60 to 1. A underdrive either 2 to 1 or 2.5 to 1 would double my crawl ratio to 120 to 1 or 150 to 1 which would be one heck of an upgrade without having lengthen my Transmission, Tcase combination. When I heard 2 of my friends talking about it, it seemed like something thats been done before. I'll have to keep doing some digging.

    O_Negative
     
  7. Nov 17, 2010
    Rralphs

    Rralphs Old Member

    Nederland, Co
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  8. Nov 17, 2010
    O_Negative

    O_Negative New Member

    Montana
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    The problem with the Klune is the overall length of the transmission and t case. Where as an underdrive that goes in the pto port would give you the same length but give you more gear reduction.
     
  9. Nov 17, 2010
    Mcruff

    Mcruff Earlycj5 Machinist

    Albertville, AL
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    I have to ask, what in the world do you want a 120-150 crawl ratio for. I realize that is normal in rock crawling competitions but realisticlly 60-70:1 is plenty for 98% of wheeling that normal people do.
     
  10. Nov 17, 2010
    Warloch

    Warloch Did you say Flattie??? Staff Member

    Falcon, CO
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    I am just over 78:1 and only use it about 5% of the time. The rest of the time I am using from @ 20 - 42:1.

    IMOP anything more than about 80 is a waste of time, effort and funds unless your doing it on a pro level.
     
  11. Nov 17, 2010
    Long&Low

    Long&Low Active Member

    Geauga County, OH
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    I had a YJ that had near a 175 to 1 crawl ratio, at times it was fun in real big rock or on real steep climbs. BUT, you also need grip, or you'll just sit and spin. With all that gearing i had four shifters, it can be a mess keeping things straight. (Ford NP435, a flipped Dana 300 mated to a NP203 reduction box with 4.88 axle gears). I really liked the NP435, but first gear was un-usable on the street.

    I agree with Mcruff, anything between 60-70 is pretty darn acceptable and usable.
     
  12. Nov 18, 2010
    O_Negative

    O_Negative New Member

    Montana
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    The main reason I'm looking is more options, I have friends that run 200:1 in their trail rigs, and they need it. The off road park here has some very challenging obstacles where a high crawl ratio is a necessity. I've done everything I can to strengthen my drivetrain other than a trannsmission swap. I've narrowed a Wagoneer D44 to CJ width, converted it to 5 lug, and put chrome moly axle shafts with yukon gear super joints. The rear is a factory offset D44 that was flanged but I converted to full floating. I've broken 1 chrome molly front and one full floating rear. My biggest disadvantage is my lack of gearing, and the shock I have to put on my drivetrain to get over the obstacles. The more options I have for gear ratios the better my chances are of finding one that will work for specific situations. I know the SM465 swap will help me tremendously, but I would like to find a way to get into the crawl ratios my friends with doubled T-Case Toyotas are getting into.

    O_Negative
     
  13. Nov 18, 2010
    oldtime

    oldtime oldtime

    St. Charles,...
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    Last edited: Nov 18, 2010
  14. Nov 18, 2010
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    I remember the Ranger, just the adds in magazines; no experience with one.
    They installed between the trans and t/case if I recall.
     
  15. Nov 18, 2010
    unclebill

    unclebill Banned

    a sun blasted...
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    i hardly ever use mine.
    But i like it..... :D
     
  16. Nov 19, 2010
    wuze

    wuze lost in austria

    austria-europe
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    i have 225, t15, d18 and 3.73 and i look also to get a better crawl ratio because 28 is not so fine in the rocks of the rubicon :D
    i had in my tj 98 to 1 and i have loved it.

    i wish i can get these 4:1 gearing for the d18.
    http://www.earlycj5.com/forums/showthread.php?t=21389

    gerald
     
  17. Nov 19, 2010
    66cj5

    66cj5 Jeep with no name

    NorthWest Indiana
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    rather then look for an underdrive, I would regear your axles to 5.38 and add an OD.

    I wasn't happy with the t14/3.73 combo (unless I was in sand), but the 4.27/OD meets 98% of my needs.
     
  18. Nov 19, 2010
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    To Gerald, you could double your crawl ratio with 3:1 Tera gears and 5.38 axle gears. Herm sells overdrives that are compatible with the Tera gears. You'd need about 3000USD for parts, plus the shipping and installation. All readily available parts though.

    To the OP, how about some portal axles? Moggie comes to mind...

    I kind of doubt that you could easily redesign the Warn OD to be an underdrive. Planetary transmissions are not ammenable to such changes. I think you may as well design an all-new UD...

    However! I expect that a good machinist could adapt the Quadratrac low range unit to couple to the Dana 18. They are quite plentiful, as such things go, and would give an additional 2.57:1 reduction.

    [​IMG]
     
    Last edited: Nov 19, 2010
  19. Nov 19, 2010
    AKCJ

    AKCJ Active Member

    Fairbanks, Alaska
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    Bingo. This would be the easy (cheap) way out.

    I was skeptical about a need for lower than ~75:1 but you explained your situation and now I understand what you're trying to do.

    Good Luck.
     
  20. Nov 19, 2010
    Rralphs

    Rralphs Old Member

    Nederland, Co
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    They still sell the Ranger. They mounts between the bell housing and the transmission.
    http://advanceadapters.com/category/28/Ranger+Torque+Splitter+Overdrives+&+Underdrives.html

    Also too long for early CJ's.

    As to changing a warn overdrive to an underdrive, would it be worth the effort to get the inverse of .75 ratio (1.33 reduction).

    Getting a t18 or some other granny tranny is more bang for the buck.
     
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