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Best Gears

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

?

Which gears?

  1. 3.73

    17 vote(s)
    56.7%

  2. 4.27

    13 vote(s)
    43.3%
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  1. jpflat2a

    jpflat2a what's that noise?

    I drove a members Jeep up a steep incline at elevation that was 304,T15,D20,3.73's.
    In low range it was a struggle power wise to get up the hill.
    The owner asked me to drive it because he couldn't get up the hill.
    I was shocked at how inept it was, even in low range.
     
    jpflat2a, Feb 22, 2017
    #21
  2. ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    I think the key info here is 31" tires.
    If we were talking 33s or 35s, 4.27s would be obvious. But if you're after comfort, and the majority of the usage is street, I don't think the minimal gain in crawl ratio would be worth the extra rpms and fuel usage that 4.27s would give you.
    For final crawl ratios, we're talking 22.38:1 with 3.73s vs. 25.62:1 with 4.27s. They're both pretty bad, so I'd go with the better road gears.
     
    ITLKSEZ, Feb 22, 2017
    #22
  3. Keys5a

    Keys5a Sponsor

    The D20 has something like a 2:03 low range, and the T15 has about a 3:00 first gear. That was part of the problem.
    I drove my old Tux for years with a Buick 215 V8 with the 4:27 gears with 29" tires. It was a great combination both on the road and pulling on the beach.
    -Donny
     
    Keys5a, Feb 22, 2017
    #23
  4. 47v6

    47v6 junk wrecker! 2023 Sponsor 2022 Sponsor

    I run 5.38 with 35" tires. I have an SM420 and that combination with the low gear makes it ok. No OD.
     
    47v6, Feb 23, 2017
    #24
  5. shaun

    shaun Member

    4.88 I think? Running 33 x 12.5 x 15. This is what I found upon opening the diff.

    [​IMG]
     
    shaun, Mar 5, 2017
    #25
  6. ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    43/8=5.375 (5.38:1)
     
    ITLKSEZ, Mar 5, 2017
    #26
  7. timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Yep.
     
    timgr, Mar 5, 2017
    #27
  8. duffer

    duffer Rodent Power

    How much low end torque is available from a 327, like any other engine, depends on how it is built. It should be better than a 305 in just about every way unless it is 11:1, solid lifter 7K cam, and big heads and then used on some real trails. No reason you can't put one together that will run just fine at 500 rpm. For the record, I did have one of those hot 327's in my B for a spell but was running 5.38's and the OD. It did do trails but wasn't the most happy camper around------ On the street it was really fun in a flat fender that looked completely stock, including the rust and peeling paint. Geeze was that a looooong time ago.

    I would likely opt for the 373's and invest in the TeraLow gear set for the D20.
     
    duffer, Mar 5, 2017
    #28
    FinoCJ likes this.
  9. FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    3.73 gears on the street with v8 304 T15 and 31s seems like a good set-up, although if I were buying I'd probably go with 4.27s as it seems getting enough gear ratio is always a focus - but I'd probably be running 33s and using it off road more than street.

    But in either case with the 2:1 D20, it may need more off road, low end grunt, then a 4speed granny is ideal....but in my case swapping in Tera Low gears was a feasible solution that didn't require a R&P gear change on both ends or the mods needed for the transmission swap. The 2:1 D20 will get a bigger improvement with the 3.:1 Low gears than my D18 (only 2.46 to 3.1 improvement).
     
    FinoCJ, Mar 7, 2017
    #29
  10. windyhill

    windyhill Sponsor

    4:27's because we all know your not going to stay with 31's on a cj6....Seriously how much time are you going to spend at 70mph.
     
    windyhill, Mar 11, 2017
    #30
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