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Transmission Ranging

Discussion in 'Flat Fender Tech' started by oldtime, Jan 7, 2021.

  1. Jan 8, 2021
    duffer

    duffer Rodent Power

    Bozeman, MT
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    There are some relatively accurate computer dyno simulations out there if you have accurate data for the inputs. I used Comp Cams Dynosim5 to put together the 441 bucket list engine. A very useful exercise to avoid picking parts that aren't going to yield the results you are looking for. But as with a real dyno run, those results are still WOT and, IMO, only loosely related to the real world, especially if what you are looking for is low rpm torque.
     
  2. Jan 8, 2021
    oldtime

    oldtime oldtime

    St. Charles,...
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    Thanks John, I can sure see where torque testing would problematic under WOT conditions.
    My tests would be to take the the running engine and fine tune the engine at idle via distributor adjustments. Then finally do a bit of carburetor tuning.
    Then go out and drive the vehicle at various speeds and tromp down on the accelerator.
    Speed producing the most “G” forces = highest torque output.
    So then how does one accurately test the “G” forces.
    Carry a long a gold fish bowl and when the fish pops out your done ?
     
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  3. Jan 8, 2021
    Jw60

    Jw60 Sitting up n buckled down. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sedalia MO.
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    there is a Dyno 30 miles away from me in warrensburg...
    I feel like any tests at speed would give the advantage to lower end due to wind resistance.
    You would need to have a variety of gear selections that overlap at the same ground speed and record vacuum readings.
    Or if you have a PTO and really big water pump you could make a dyno.
     
  4. Jan 8, 2021
    AKjeff

    AKjeff Member

    Carson Valley, NV
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    I have long thought the close ratio T19 would be a fine transmission in a jeep or even a pickup, due to the 4:1 first gear ratio.
    I suspect the SM465 is easier to find, and still gives a lower take off ratio in 2nd (3.58:1) than my T14 does in 1st. For that matter it has a lower 2nd gear ratio than the T18 as well.

    I consider take off ratio, particularly when increasing tire size, to make life easier on the clutch.
     
  5. Jan 9, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Just throwing my 2cents of experience in with so called 'take-off' ratio for the street....with the v6/T14/4.88/33s....standard take-off ratio of 3.1x4.88 yields 15.1, and I find that is too low for city street driving and I can barely get into the intersection before shifting gears and getting run-up my tailpipe by the car behind me. I often use the OD (75% reduction according to AA for the Saturn unit), which improves the take-off ratio to 11.3....If I were running smaller tires (say 30s), then I think I would want to reduce (numerically) the take off ratio even more - maybe something close to 10. I am looking at using a 4:1 T18 into the cj5 as the street take-off in 2nd gear would be 2.41x4.88 = 11.76. This still might be a bit more gearing than is needed, but I like that I might reduce the use of the OD for street driving to reduce wear and increase longevity. As for the full 'ranging', the 4.0 1st gear combined with the 3.15 tera low gears will yield a CR of 61.5 (nicely improved from the current 48 with T14). I get the highway rpm cruise down with the OD....for 65mph with 33s/4.88s/.75 OD that means rpm of just over 2400 rpm (T14 or T18 is the same for this), and of course, the strength and durability of the T18 is also an improvement over the T14, and the jeep t18 should mate to the D18 without an adapter....Realistically, I think the 33s are more like 31-32, so when I am happy cruising 24-2500 rpm, I am probably just under 65mph, which is fine for my ross steering and drum brakes....

    Taking this a bit further....I am thinking about the 58 willys....the sbc350 will probably produce more low end torque and its currently running 30" tires. The street-take off should probably be around 10. With the sbc283, the t90c 3.1 first and 4.29 gears yields a take-off of 13.3, which was a bit too low for my city driving around here. I am working on swapping to the sm465, as there are advantages to the sm465 as a cheap native mating transmission, but I don't particularly like the gear ratios for a more street driven vehicle. Obviously, the granny low 1st is not part of the daily driving, but the 3.58 2nd gear is concerningly low for street take-offs...combine that with the 4.29 gears yields a take-off of 15.4....In the long run, higher axle gears would probably be a nice solution, but guessing I will use an OD on the D18 to try and get the take-off down to 11.5, and possibly some taller tires some day. As I hope the wagon will be a good cruiser, 70mph on the highway with 31.5" tires (235/85/16)/4.29/OD will require 2400 rpm out of the v8. Sad part is that with the 6.55 1st, it will have a better CR than the CJ at 69.1.
     
    Last edited: Jan 9, 2021
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  6. Jan 9, 2021
    oldtime

    oldtime oldtime

    St. Charles,...
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    Thanks FinoCJ, that’s exactly what I was hoping to hear. Someone who likes a faster street “take off ratio” than the old slow Willys 15/1.
    I am so used to the old 15/1 that I really have no experience with faster take offs.
    So I take it that for city driving you think 11.5/1 is about ideal on 32” diameter tires.
    That is very good to hear because o have crunched a lot of transmission, transfer case and differential numbers that come in around 11 something /1.
    The 11 something /1 take off ratio combinations seem to be especially common when running 3.73 differentials.
    If running a D20 at hiway speeds I feel that 3.73’s or 3.54’s is the only way to go.

    Here I decided to make a chart showing all of the CJ street “take off “ ratios 1945-1979.

    1945-1963 T90A x 5.38 = 15.0/1
    1956-1963 T98A -A (option) x 5.38 = 16.6/1
    1963-1965 T90C x 4.27 = 14.3/1
    1963-1971 T98A (option) x 4.27 = 13.2/1
    1966-1967 T86AA x 3.73 = 10.4/1
    1966-1967 T86AA x 4.89 (option) = 13.7/1
    1967-1975 T14 x 3.73 = 11.6/1
    1967-1971 T14 x 4.89 (option) = 15.2/1
    1970-1975 NR T18 x 3.73 = 15.0/1
    1972-1975 T14 x 4.27 (option) = 13.2/1
    1972-1975 T15 x 3.73 = 11.1/1
    1972-1975 T15 x 4.27 (option) = 12.8/1
    1976-1979 T150 x 3.54 = 10.6/1
    1976 NR T18 x 3.54 = 14.2/1
    1977-1979 WR T18 x 3.54 = 10.9/1
     
  7. Jan 9, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    Yes - I certainly wouldn't go any lower geared (numerically higher ratio) than 11.5/1.....I don't have any actual experience with something in the 10.5-11:1 range, but I would guess that for street driving, it would be good. I dug through my tacoma specs as I find its a bit too low geared for street take-off as well with 32s....turns out its about 15:1 with the 4.2 first gear and 3.73 axles....2nd gear is 2.2 which yields 8.2 and requires a lot of clutch burn....so something between 10.5-11.5:1 seems like a good place to be....
     
    Last edited: Jan 9, 2021
  8. Jan 9, 2021
    73 cj5

    73 cj5 Not ready for the junkyard yet

    Clinton, Mississippi
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    My 81 CJ5 had a 9/1 first gear. It was horrible, especially on hills. Personally, I don't like the 14/1 of the t90c and 4.27's with the f134.
     
  9. Jan 9, 2021
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    This really comes down to engine choice, where a one size fits all approach won’t work.

    My 15:1 first feels great in my 4cyl CJ with an engine that has no problem winding out to 4, 5 or even 6k rpm. Like Fino stated, that might not be ideal when coupled with an engine with gobs of low-end torque that is suffering past 3 or 4k.

    The 225/t86/3.73 combo (10.4:1) in Mighty Mouse was ok, but i found myself idling while riding the brake in parking lots, and the low range gearing was awful. But everyday driving was fine, aside from the too-wide split between 2nd and 3rd.
     
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  10. Jan 9, 2021
    oldtime

    oldtime oldtime

    St. Charles,...
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    Well I sure don’t wanna ride the brakes in the parking lot.
    I know the 15/1 ratio rolls right over speed bumps without needing brakes.
    But I will surely consider speeding it up a little.
    Dauntless torque should have no problems with most any of the ratios posted.
     
  11. Jan 9, 2021
    73 cj5

    73 cj5 Not ready for the junkyard yet

    Clinton, Mississippi
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    I'd say vehicle weight and tire size comes into play right along with the engine choice.

    This is more opinion based as far as the ideal ratio goes.
     
  12. Jan 9, 2021
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Pullman, WA
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    I've got a '68 with an odd-fire 231 and a '71 with a Buick 350 that both have the original T-14/3.73 setup. For street driving, I think the 11.6:1 take-off gear is perfect. I do find it to be a little high when offroad in hi-range though. A 15:1 would be better for that.

    That said, the plan is to got to a T-98/od/4.88 setup in the '71. 2nd gear starts in high range are right at the 15:1. Here's all the gears with that combo in order of ratio:
    • 1/low 76.83
    • 1/low/od 57.62
    • 2/low 37.09
    • 1/hi 31.23
    • 2/low/od 27.82
    • 1/hi/od 23.42
    • 3/low 20.29
    • 3/low/od 15.22
    • 2/hi 15.08
    • 4/low 12.00
    • 2/hi/od 11.31
    • 4/low/od 9.00
    • 3/hi 8.25
    • 3/hi/od 6.19
    • 4/hi 4.88
    • 4/hi/od 3.66
    Lots of overlap between hi/low range which is a little odd, but it gives you a wide range of speeds in low with out having to stop and shift to hi. Interesting the T-98 1st/hi is that same as my current 1st/low with the T-14/3.73 gears.

    It is tempting to not do the over drive and leave the 3.73 gears. That makes the following gears:
    • 1/low 58.73
    • 2/low 28.35
    • 1/hi 23.87
    • 3/low 15.51
    • 2/hi 11.53
    • 4/low 9.18
    • 4/h 3.73
    But, I like havng 4 shift levers and extra gears to play with.
     
  13. Jan 9, 2021
    Jw60

    Jw60 Sitting up n buckled down. 2024 Sponsor 2023 Sponsor 2022 Sponsor

    Sedalia MO.
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    I agree this will never be a one size fits all especially when you factor in topography.
    The 134 t90a and 5.38s were great in upstate NY but way too low for MO.
     
  14. Jan 9, 2021
    FinoCJ

    FinoCJ 1970 CJ5 Staff Member

    Bozeman, MT
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    all True...but as oldtime is looking to run a 225v6 with 32s, our set-ups are pretty close so there is some viable comparison....

    Not sure 15:1 really works off road much better....maybe dirt road cruising or snow pack, but basically, if 4wd is needed here on the mountain trails, low range is also needed. A true granny low would give some option to run 4hi though.....my jeep rids so rough on 4wd trails (even with BDS and aired down) that low range is required just to go slow enough to make it pleasant....
     
  15. Jan 9, 2021
    Fireball

    Fireball Well-Known Member 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    I meant more for steeper parts around our property where you don't need to be in 4 low, but you have to slip the clutch noticeably to get going. It's not an issue on the road. Like you say though, then I usually drop it into low range.
     
  16. Jan 10, 2021
    oldtime

    oldtime oldtime

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    Yes, for now I’m totally sold on flatties powered by the Dauntless on 32” skinny’s.
    I have two fully built engines and 3 sets of new tires in waiting. So that will not change.
    But I’m still considering various ways to gear them.

    For the gear train I have:
    Two WR Jeep T18’s and also have a Jeep T15 ready to go. Maybe find and try a NR T19 ?

    A nice freshly built 2.46 twin stick big hole D18 with tapered intermediate bearing kit.
    Ditto the above D18 but with Tera Low gears.
    Have Rebuilt Warn overdrives and a pto adapter for both D18’s. Can run the overdrives with 2.46 or 3.15.
    Also have a special built Tera Low D20 with DS factory twin sticks and parking brake.

    3 sets of rear axles still being assembled, all with Powr Lok.
    A D44 center flanged with 3.73 gears and two D44 offset flanged axle assemblies with 4.89 gears.
    All front axles are Powr Lok D30’s.

    My cruise ratio is already determined.
    I’ll go 3.73 with the D20.
    With the D18’s (4.89 x .75) I’ll end up with 3.66.

    The only thing I can change now are the street take off ratios and the crawl ratios.

    Enough stuff to complete 2 more daily driver flatties with a few extra parts.
    I plan to build them with different geartrain combinations and see what I like the best.
    Probably my next build will use the easier shifting T15 and a Tera Low D18.
    If that’s too noisy I may try to quiet it with 2.46 gear set and a WR T18 for better crawl gears.
    Then if still too noisy I can just drop in the silent type transfer case.
     
  17. Jan 10, 2021
    ojgrsoi

    ojgrsoi Retired 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    I am impressed. :watch: I work pretty hard to figure how to get my stuff to move, stop and steer. :shrug: Youse guys just amaze me with all the thought and numbers. :study: :schooled:
     
  18. Jan 10, 2021
    Jw60

    Jw60 Sitting up n buckled down. 2024 Sponsor 2023 Sponsor 2022 Sponsor

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  19. Jan 10, 2021
    colojeepguy

    colojeepguy Colorado Springs

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    Agreed. I do the same thing, except my T90 has an even more anemic 2.79 1st gear, which puts me at 10.21. The 225 can pull that just fine, unless it's a steep hill, then I use straight 1st.
     
  20. Jan 11, 2021
    RATTYFLATTY

    RATTYFLATTY I think you need a little more throttle

    Central MN
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    To add my .02 I run a 225/6.32 T18/2.46 low Dana 20 with 4.10 gears and 33" tires. Around town I run it as a 3 spd, with the 3.09 2nd that puts me at 12.67 for a take off ratio which seems to work great for me. I don't have a tach in the Jeep so I cat tell you the runout RPM's for the HWY driving. I do get out on the freeway at times and I'm sure the RPM's are up there. I don't find myself holding up traffic but then again I'm not passing anyone either.
     
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