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Best Gears

Discussion in 'Early CJ5 and CJ6 Tech' started by 56cj6, Feb 20, 2017.

?

Which gears?

  1. 3.73

    56.7%
  2. 4.27

    43.3%
  1. Feb 20, 2017
    56cj6

    56cj6 New Member

    Ventura CA
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    Nov 1, 2016
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    Hey guys I have a 56 cj6. Currently have a Chevy 327, t-15, Dana 20 transfer case, 31 in tires. I have 2 sets of axles and am debating which once I want to put in. One set has 3.73 gears and the other has 4.27. What do you think is best. It's going to be 60% street , 40% dirt use.... nothing serious and no rock crawling. Please let me know. Thanks!
     
  2. Feb 21, 2017
    jeepermc

    jeepermc Active Member

    Western WA
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    1,188
    For cruising with a V8 and 31's with no OD, I vote 3.73's. 4.27's will put you close to 3k rpm cruising on the freeway.
     
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  3. Feb 21, 2017
    rejeep

    rejeep Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Rochester, NY
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    on the money
     
  4. Feb 21, 2017
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    If it were mine, I would go with the 4.27 gears. Tell us more about the axles. A set of open Dana 30 / flanged Dana 44 axles with 4.27 gears is a desirable pair of axles.

    How fast do you want to drive? 3000 RPM will be somewhat noisier than 2500, but it should not make much difference to the engine. Insulate the floor, use a quiet fan, use a quiet exhaust, use quiet tires ... no problem.
     
  5. Feb 21, 2017
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    Swap one rear in and drive it around; don't like it, try the other.
    When satisfied, then install the front axle.
    Costs you nothing but time.
     
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  6. Feb 21, 2017
    oldtime

    oldtime oldtime

    St. Charles,...
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    Dana 20 overdrives are extremely scarce and little more than a novelty item.
    So I think 3.73 ratio is right near the goal for a daily driver on hiway seeking optimum fuel mileage.
    If used mostly for local commutes and or solely to get to the trail head then 4.27 is a better bet.

    Do as Jim suggest above then report back here to us with your experienced opinion.

    You might also consider adding Tera 3.15 gears to the Dana 20.
     
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  7. Feb 21, 2017
    daddyusmaximus

    daddyusmaximus New Member

    Indiana
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    Feb 7, 2017
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    3.73 unless you change to 75% off road duty.
     
  8. Feb 21, 2017
    rusty

    rusty Well-Known Member

    norfolk,va
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    I'm running 3.73's in my 75 and kind of like them. If I were doing a lot of off road driving. the 4.27's would be better.
     
  9. Feb 22, 2017
    56cj6

    56cj6 New Member

    Ventura CA
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    Nov 1, 2016
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    Thanks for the replies guys. I think I will put in the 3.73 then. Majority of my driving will be around town with the occasional off-road. Definitely need to be able to cruise at highway speeds because I'm driving my JEEP to the trails. if it feels way to high then there's always the option of swapping but I'm trying to avoid that
     
  10. Feb 22, 2017
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    Interesting how split this is....
     
  11. Feb 22, 2017
    Rick Whitson

    Rick Whitson Detroit Area 2024 Sponsor 2022 Sponsor

    I live South of...
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    I have 3:73's in my 64 Tuxedo Park, with a 134 F head, T-90 , T18, and 750 X 15" tires. I use it for Forest viewing on trails, and cruising to town for parades and shows. It will sustain 50 mph without straining on the roads and cruise the trails at low speeds well too. The club where our cabin is has 11,000 acres of hunting land, and 2,000 acres of cabin land, the max speed is 20 mph anywhere on the property, so it is in second gear a lot.
     
  12. Feb 22, 2017
    colojeepguy

    colojeepguy Colorado Springs

    At the foot of...
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    Is there such a thing? I have never seen one.
     
  13. Feb 22, 2017
    jpflat2a

    jpflat2a what's that noise?

    Hermosa, SD
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    You'll miss those 4.27s off road.
    Oh yea, I have 5.38s and drive to most trails.
     
  14. Feb 22, 2017
    oldtime

    oldtime oldtime

    St. Charles,...
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    Yeah its a really tough call....
    On road 3.73 is way better but on trail 4.27 is way better.
     
  15. Feb 22, 2017
    rejeep

    rejeep Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Rochester, NY
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    that's it pretty much what it comes down to... and if your being honest with yourself about the road/trail split the answer is fairly clear..
     
  16. Feb 22, 2017
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I voted for 4.27 but in reality unless the 327 is anemic it should do pretty well at just above idle speed with 3.73 gears.
     
  17. Feb 22, 2017
    Rich M.

    Rich M. Shoe salesman 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Maryland
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    Mmmm. With t-15 I'd go 4:27. 327's Dont mind reving some. If you had a t-18 I'd go 3:73.
     
  18. Feb 22, 2017
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    This.
    I'd go 3.73s and keep an eye out for a 4-spd.
     
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  19. Feb 22, 2017
    jeepermc

    jeepermc Active Member

    Western WA
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    You make a good point. Dana 20's have a horrible low range gear. My dad's Flatty has a Chev 283, T-98 4 spd, Dana 18 and 3.73's. It cruises down the highway much better than my 4.27 geared flatty did, but it works great off road too because of the granny 4 spd and lower ratio of the Dana 18. Alternatively My sisters 75 CJ-5 runs a 304, 4:1 T-18 and D20 with 3.73 gearing. Also cruises great down the freeway and is OK off road, but occasionally I wish it had a lower first gear or lower low range or both. Either way, it's relatively easy to make up for lack of off road gearing with Low range T-case gearing like the 3.15 or a granny 4 spd and have the best of both worlds.
     
  20. Feb 22, 2017
    OrangeCJ5

    OrangeCJ5 Sponsor

    Taylorsville, UT
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    I think the point about the 327 not minding the extra revs is the key here. My brother had a 327 in an old '72 Chevy pickup and that thing wasn't great for grunt down low but loved the higher revs. I'd do the 4.27 gears and if it was a 305 or 350, I'd do the 3.73's.
     
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