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D18 Question

Discussion in 'Early CJ5 and CJ6 Tech' started by Posimoto, Dec 10, 2013.

  1. Dec 10, 2013
    Posimoto

    Posimoto Hopeless JEEP Addict

    Minden, Nevada
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    Is it true that a D18 with the 1 1/8" intermediate shaft is always a small hole t-case, or is there some overlap with hole size and intermediate shaft size? Basically, what I'm asking is, is it possible to have an 1 1/8" intermediate shaft with a 4" bore case?
     
  2. Dec 10, 2013
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Having torn apart literally hundreds of 18 transfer cases I have never seen a large hole case with 1 1/8" intermediate bore unless someone machined
    the input bore. Only seen 2 of those that I recall and it was pretty obvious it was not factory even though they were quite well done.


    Sent from my iPhone
     
  3. Dec 10, 2013
    oldtime

    oldtime oldtime

    St. Charles,...
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  4. Dec 11, 2013
    Posimoto

    Posimoto Hopeless JEEP Addict

    Minden, Nevada
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    Thanks guys. The reason I'm asking is I've been thinking about the TH350 that my66 has in the classifieds. It's got the Novak adapter to a small hole D18. Since I'm in the middle of doing the tapered bearing conversion on my large hole D18 I was looking to confirm that the adapter plate is for a small hole case. Sounds like it is. I've already sent an email to Novak tech support to find out how much just the adapter plate for a large hole t-case would be. That appears to be the only part that's different between the small hole and large hole D18 kit.
     
  5. Dec 11, 2013
    tarry99

    tarry99 Member

    Northern California
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    Would an ID / OD ring get you where you need to go?
     
  6. Dec 11, 2013
    Posimoto

    Posimoto Hopeless JEEP Addict

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    I think that would be a possibility. Seems like you would have to make it a press fit to the t-case. Not matter which way I look I see dollar signs.
     
  7. Dec 11, 2013
    tarry99

    tarry99 Member

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    Yep your right the old $$$$ signs , you need a bigger shop then you could have a mill and a lathe and, and, and.........you might be able to put a taper on it and match it on the other side then stake the ring in there........or a press fit and stake both sides.......it's just for locating the center I guess...the outside bolts should hold it in place.

    Automatic huh? You been listening to me?
     
  8. Dec 11, 2013
    oldtime

    oldtime oldtime

    St. Charles,...
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    On the plus side the 2 versions of the small hole D18 are more common (used from 1945-1971)
    On the minus side the small hole cases use a somewhat weaker casting.
    Personally I would wanna use a big hole and see if you can fit in a different rear bearing retainer.
    I'm not familiar with TH350.
    Maybe you could use or modify a T86AA rear bearing retainer to fit in between ???
    The T86AA rear bearing retainer will fit the Big Hole transfer case perfectly.
     
  9. Dec 11, 2013
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Some of the Novak TH-350 adapters could use either the T-90 rear bearing adapter (small hole) or the T-86 rear bearing adapter (large hole). The trans adapter was built so either would be a slight press fit. Might ask My66 if it looks like a piece is pressed into the aluminum transmission adapter.


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  10. Dec 11, 2013
    Heatseeker

    Heatseeker Member

    Calaveras...
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    Sleeving the hole wouldn't be too tough if you knew a machinist:rofl:...

    Let me know If I can help ya John.

    An automatic huh???:?
     
  11. Dec 13, 2013
    Posimoto

    Posimoto Hopeless JEEP Addict

    Minden, Nevada
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    The tech at Novak got back to me today. They actually have an adapter that I can use to size the 4" t-case to the small hole size adapter plate. $38 + shipping. I've been considering an auto tranny for awhile. The downside is I think I might need a lower low range if I go with the slush box, and I'll have to upgrade the brakes to power.
     
  12. Dec 13, 2013
    tarry99

    tarry99 Member

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    The 350 slush is what 2.52 in low gear?.........and in low gear only with the torque multiplied by about two from the converter that give's you about 5:1 in low gear...... not as good as your 6:32 but not bad either........power brakes yes but as we talked the right stall converter is what is important!
     
  13. Dec 13, 2013
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    See my above post Posimoto. I'm willing to bet the tech just wants to sell you the T-86 bearing retainer. That is fine if the adapter is machined to accept it. If not then it won't work without machining. Some of the older vintage Novak and AA adapters were machined large or small bore specific.


    Sent from my iPhone
     
  14. Dec 13, 2013
    Posimoto

    Posimoto Hopeless JEEP Addict

    Minden, Nevada
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    Terry: This project isn't something I plan to tackle right away. Probably next Winter. I'll have a lot of parts to figure out and as you mentioned, the torque converter is of primary concern. I'll have to track down a flex plate for the oddfire too. I don't know if my buddy ever got in touch with you re: the Atlas t-case, but he's also running a TH350 and he is very happy with it. What really got me to thinking about the auto was getting to drive a friends Rubicon with the auto tranny. He also has the Rubi-Crawler so gearing isn't an issue even with his 4.88 gears, which I consider a little on the high side for rock crawling.

    Nick: I'm going to call the tech at Novak on Monday and get the full story on this adapter. I hear what you are saying and if I need to have machine work done I might as well just have someone make the adapter ring for me if that's the case.
     
  15. Dec 13, 2013
    tarry99

    tarry99 Member

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    John,

    In the next few months I hope to have a pretty good handle on those Auto's although right now I'm liking the 4-speed 4L60 version just for the more friendly street use with the 30% OD in 4th..........
    I Have a 231 flex plate here that your more than welcome to.......should bolt right up and of course balance is of no concern.
     
  16. Dec 14, 2013
    Posimoto

    Posimoto Hopeless JEEP Addict

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    Terry, I sent you a PM.
     
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