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Advance Adapters D18 3.15 Kit?

Discussion in 'Early CJ5 and CJ6 Tech' started by garage gnome, Jul 11, 2021.

  1. Jul 25, 2021
    masscj2a

    masscj2a Member 2023 Sponsor

    Ware, Mass
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  2. Jul 25, 2021
    RATTYFLATTY

    RATTYFLATTY I think you need a little more throttle

    Central MN
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  3. Jul 25, 2021
    oldtime

    oldtime oldtime

    St. Charles,...
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    RattyFlat, go pick that up , I’ll definitely buy it.
    Great price !
     
  4. Jul 25, 2021
    RATTYFLATTY

    RATTYFLATTY I think you need a little more throttle

    Central MN
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  5. Jul 25, 2021
    garage gnome

    garage gnome ECJ5 welder

    Western MA
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    I was able to add it to my cart and went through all the motions of checking out other than hitting the "complete checkout" button, so I'm assuming it is possible to order it. I didn't want to spend the money right now.
     
    masscj2a likes this.
  6. Oct 12, 2021
    Dan Lockwood

    Dan Lockwood New Member

    Mid-Michigan
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    Does this kit only lower the low range, or does it also lower the high range? I know that in the Suzuki Sammy transfer case, their crawler gear sets work to reduce both low and high so when you go with larger tires, it helps out in high range too.

    Showing my ignorance, what does this kit do other than rebuild the D18 transfer case?
     
  7. Oct 12, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    It only lowers the low range...in a D18 it replaces the 2.46 low range with 3.15 reduction. Hi range stays 1:1. For a D20, it's a more significant reduction as the D20 low range is only 2.0, so a big improvement to the 3.15 reduction. The new gears are also spur cut, even in high range, so there is more gear clatter/noise when cruising, and especially in the D18 where even in 2hi, the intermediate and output gears are spinning.
     
  8. Oct 12, 2021
    Dan Lockwood

    Dan Lockwood New Member

    Mid-Michigan
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    James, thanks for the 101 class on the gear set! Would be nice "if" the high range was dropped a bit too. But I guess one could always just drop a couple grand on new diff gear sets with lockers etc... :) That would probably help for slightly larger tires etc.
     
  9. Oct 12, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Not sure what jeep you have, but these old cjs usually have pretty darn low stock gearing...mine came with 4.88s OEM so i actually added and OD so it would cruise at highway speeds. Some of the 4cyl came with 5.38s...Not sure I would want my hi-range any lower...

    edit - looks like you have a 67 cj5...not sure if its mostly original or not, but if OEM v6, then you would have either 3.73 or 4.88 gears...if 4cyl, then I think its 4.27 and 5.38 gear options. Maybe you have swapped out drivetrain or something different. How big of a tire you thinking....Most of us find 33s is kind of the max without a lot of modifications on the short wheelbase, but if your from the sami crowd, you already know about swb....
     
  10. Oct 12, 2021
    oldtime

    oldtime oldtime

    St. Charles,...
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    There is practically no way to lower the cruise ratio on a CJ without lowering the final drive ratio because underdrives are virtually non existent.
    FWIW Tera flex gear are “not” utilizing any spur gears when shifted into high range. They are helical cut. On both D18 and D20 only the low range usage engages the spur cut gears.
     
  11. Oct 12, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Hmmm...I know you are probably right, but I'll need to check my photos now to verify....
     
  12. Oct 12, 2021
    oldtime

    oldtime oldtime

    St. Charles,...
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    That said I believe the Tera flex gears are cut at a different helix angle and pitch which may be the reason Tera gears seem to be louder than standard Dana gears.
     
  13. Oct 14, 2021
    Dan Lockwood

    Dan Lockwood New Member

    Mid-Michigan
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    James, not real sure yet as to exactly what I have. I'm going to be crawling around under it this weekend I believe. As of right now, it appears to be all original from the Hurricane 134 back to the D44 rear two piece axle rear end. Although some changes to the front fenders and tail lights seem to have been made. I'll try to get more info/pictures this weekend about what's original and not.

    Do they ever tag the housings or stamp the ratio on the diff?

    Thanks again for all the information!

    Dan
     
    FinoCJ likes this.
  14. Oct 14, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    The axles would originally have had tags on the diff cover....but guessing many have long since been lost, and who knows what's been changed no matter what the tag says. You can jack up one wheel and spin the tire and count driveshaft revolutions or just remove the diff cover and the ring gear should have the stamping on it for tooth count. F134 would have had either 5.38 or 4.27 gearing originally. A 4cyl with 31s and 5.38 gears is a pretty nice set-up, even if not a fast highway cruiser.
     
    Twin2 likes this.
  15. Oct 26, 2021
    Steve Ryan

    Steve Ryan New Member

    Foresthill,ca
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    Who is Herm? I would like to find out where he is with the gear reproduction.
     
  16. Oct 26, 2021
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
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    Steve Ryan likes this.
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