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Ari Holopainen / gearbox1 | |
| BASIC & SPECIAL DESIGNS Here is first three types of basic designs: some auxiliary gearboxes, main gearboxes and transfer cases. Auxiliaries are used in trucks and tractors to give more gears and larger speed range. Main gearboxes are heart of truck and tractor transmissions, and they have usually geometrical gear steps. So they differ from personal car gearboxes which have progressive gear steps. There are also some transfer cases for off-road vehicles. Then there is three types of special designs: gearboxes with 2-speed motor, flat gearbox designs where axles use only one or 1,5 layer vertical space and race transmissions. Table of Contents: A. Auxiliary Gearboxes - A.1. Range-change unit, gear step 5,00 - A.2. Range-change unit, gear step 4,50 - A.3. Range-change unit, gear step 4,00 - A.4. 4-speed range unit for tractor - A.5. Splitter unit, gear step 1,25 - A.6. Splitter unit, gear step 1,20 - A.7. Auxiliary 3-speed gearbox, compound splitter/range-change unit B. Main Gearboxes - B.1. Basic 5-speed synchromesh gearbox, overall gear ratio 9,00 - B.2. Basic 6-speed synchromesh gearbox, overall gear ratio 3,47 - B.3. Basic 3+R-speed synchromesh gearbox, overall gear ratio 3,00 - B.4. 5+R-speed synchromesh gearbox, overall gear ratio 4,00 - B.5. 5+R-speed synchromesh gearbox, overall gear ratio 3,33 - B.6. 4+R-speed synchromesh gearbox, overall gear ratio 3,00 - B.7. Simple 2-speed synchromesh gearbox version A & B, gear step 1,71 C. Transfer Cases - C.1. Version I - C.2. Version II - C.3. Version III - C.4. Version IV - C.5. Version V [Shortcut to A.-C.] D. Gearboxes With 2-speed Motor - D.1. 10-speed with splitter for truck - D.2. 10-speed version II B for truck - D.3. 4-speed version B for muscle car - D.4. 5-speed version B for personal car - D.5. 6-speed version B for van - D.6. (reserved for 7-speed version B for coach) E. Flat Gearbox Designs - E.1. Basic 8-speed for mid range truck - E.2. Small step 16-speed for linehaul truck - E.3. 14-speed for heavy duty truck - E.4. Basic 8+8R-speed for tractor - E.5. Basic 8+4R-speed for tractor - E.6. 16+8R-speed with splitter for tractor - E.7. 12+8R-speed with creeper for tractor F. Race Transmissions - F.1. 4-speed drag race version I - F.2. 4-speed drag race version II - F.3. 3-speed drag race - F.4. 4-speed NASCAR [Shortcut to D.-F.]
A. Auxiliary Gearboxes: Here is updated small collection of auxiliary gearboxes that are used in trucks and tractors together with main gearboxes. All designs are quite basic so you don’t need old 14 teeth thin bevel gears or new 28 teeth gear. Although all designs have brick frame they should be possible to build with studless frame. A.1. Range-change unit, gear step 5,00: Using examples: -heavy duty 10-speed (5x2) -heavy duty 12-speed (2x3x2) -severe duty 14-speed (2x3x2+2)
These two setups are 2-speed range-change units, which are used in heavy truck transmissions as an auxiliary gearbox. Range-change unit’s idea is to enlarge main gearbox’s speed range by adding two different ranges. So you can shift main gearbox through twice, first in low range and then in high range. Real range-change unit is pneumatic-operated preselector gearbox which shifts when main gearbox goes through neutral. These lego designs are not so clever, they are only mechanical and non-preselective. Available is two setups: direct drive synchromesh and direct drive sequential. Low ratio is 5,00 and high ratio 1,00 which gives quite large range gear step 5,00.
Note the shift lever position locking method in sequential setup. Idea is that shift lever axle goes slightly inside technic plate’s hole. When shifting you tilt lever to free it, move axle to new position and lock lever in another hole. It is simple and useful for all sequential sliding axle gearboxes. Other notable thing is that in direct drive synchromesh 12 teeth double bevel gear can be replaced with two 14 teeth thin bevel gears. This gives gear step 4,29 which can be used for example in heavy duty 16-speed transmission. A.2. Range-change unit, gear step 4,50: Using examples: -linehaul 10-speed (5x2) -severe duty 14-speed (2x3x2+2) -heavy duty 16-speed (2x4x2)
Here is three setups of another 2-speed range-change unit. Setups are: direct drive synchromesh, direct drive sequential and underdrive sequential. In direct drives low ratio is 4,50 and high ratio 1,00. In underdrive low ratio is 6,00 and high ratio 1,33 and it suits to high speed motor design. So gear step in these setups is middle-sized 4,50.
One note is that direct drive sequential can be difficult to shift to high range due to S(16)-S(16) spur gear pair. When problem occurs run motor shortly to move gear wheels’ teeth in new position and try shifting again. A.3. Range-change unit, gear step 4,00: Using examples: -8-speed & 9-speed (4x2 & 4x2+1) -heavy duty 14-speed (2x3x2+2) -linehaul 16-speed (2x4x2) -heavy duty 18-speed (2x4x2+2) -6+2R-speed & 8+2R-speed tractor (3x2 & 4x2)
Range-change unit with gear step 4,00 is quite versatile design. It can be used not only in many truck transmissions but also in some tractor transmissions. Available is three setups: direct drive synchromesh, direct drive sequential and underdrive sequential. In direct drive ratios are 4,00 and 1,00 and in underdrive design 6,00 and 1,50.
In underdrive version gear wheels are chosen so that you can easily add a third ratio in this gearbox. In that case you convert range-change unit to 3-speed splitter/range-change unit. Check A.7. Auxiliary 3-speed gearbox for further information. Range-change unit’s gear step can be also smaller than 4,00. Usually 10-speed and 12-speed heavy duty transmissions need largest range step while transmissions with crawler gear(s) can use smaller range step. A.4. 4-speed range unit for tractor: Using examples: -16+16R-speed tractor (4x4) -12+4R-speed tractor (3x4)
These are 4-speed range units (ranges A, B, C and D) and designed for tractor use. Available is both synchro and sequential design. Range steps A-B and C-D are both 2,00 but step B-C is only 1,50. Notable thing is that step B-C is smaller on purpose not because of simpler lego design. Idea is taken from John Deere’s transmissions and it’s to get more gears for field working speeds 4-12 km/h.
Other note is that these range units are designed to use only with main gearboxes. Gear steps 2,00 are simply too large for using these designs as single gearbox. These designs have replaced original sequential design in which all gear step were 2,00. If you still need that original design you can check main gearboxes of 12-speed Twin Splitter transmissions on main page. A.5. Splitter unit, gear step 1,25: Using examples: -12-speed (2x3x2) -14-speed (2x3x2+2)
Splitter unit is a different kind of auxiliary gearbox used in trucks. Its idea is to double the number of gears and halve the gear steps. Real splitters are pneumatic-operated preselector gearboxes which shift when you press clutch pedal (synchromesh gearbox) or cut torque in drive line (non-synchro gearbox). Again lego designs are only mechanical and non-preselective.
Available is three setups: direct/overdrive synchromesh, direct/overdrive sequential and underdrive sequential. Direct/overdrive designs can be used two ways: in direct mode low ratio is 1,25 and high ratio 1,00 but in overdrive mode (swapped input and output) low ratio is 1,00 and high ratio 0,80. Underdrive design is for high speed motor use and its low ratio is 2,50 and high ratio 2,00. One note about underdrive sequential is that shifting to low ratio can be difficult due to XS(8)-S(16) spur gear pair. If problem occurs drive motor shortly to turn gear wheels’ teeth in new positions and try shifting again. This splitter gear step 1,25 splits equally main gearbox’s step 1,56 and it’s useful for main gearbox steps 1,50-1,67. This leads to compound shift steps 1,20-1,33. If you want to enlarge overall gear ratio by adding progression in gear steps lower gears can have as high step as 1,80 (gives compound shift step 1,44). In heavy duty 12-speed splitter’s step can be larger like 1,28 or 1,31 when using geometrical gear steps. Also larger splitter step (1,36) can be in 10-speed splitter-type transmission (5x2). Examples can be checked from main page: splitter step 1,28 is in A.4. 14-speed transmission version IV, step 1,33 in L.2. 12-speed version IIA & IIB and step 1,36 in M. 10-speed transmission. A.6. Splitter unit, gear step 1,20: Using examples: -16-speed (2x4x2) -18-speed (2x4x2+2) -16+8R-speed tractor (2x4x2)
This splitter’s gear step 1,20 suits to transmissions with lots of gears, it can be used in 16-speed and 18-speed trucks or as mechanical splitter of 16+8R-speed tractor. In tractor use splitter is used for more accurate working speed control, not for splitting main gears while driving.
Available is three setups: direct/overdrive synchromesh, direct/overdrive sequential and underdrive sequential. Again direct/overdrive designs can be used two ways: in direct mode low ratio is 1,20 and high ratio 1,00 but in overdrive mode (swapped input and output) low ratio is 1,00 and high ratio 0,83. Underdrive design is for high speed motor use and its low ratio is 2,00 and high ratio 1,67. Notable thing in direct/overdrive sequential is that shifting can be difficult due to XS(8)-S(16) and S(16)-S(16) spur gear pairs. If problem occurs drive motor shortly to turn gear wheels’ teeth in new positions and try shifting again. Splitter step 1,20 splits equally main gearbox’s step 1,44 and it’s usable in main steps 1,40-1,50 which give as compound shift steps 1,17-1,25. Crawler gear’s step in 18-speed transmission can be larger 1,67 without getting too large compound step (acceptable 1,39). In 18-speed transmission splitter step can be even smaller 1,17 but here is no examples of it. A.7. Auxiliary 3-speed gearbox, compound splitter/range-change unit: Using examples: -13-speed (4x3+1)
This one is a 3-speed auxiliary gearbox with compound splitter and range-change unit. Structure is based on range-change unit where splitter unit is available in high range only. The idea is to get progressive-like gear steps for truck transmission use. Available is both original sequential setup and alternative synchro setup. Sequential design has underdrive ratios: Low range (LO) has ratio 6,00, ratio in high range with splitter low (HI-L) is 1,50 and splitter high (HI-H) 1,25. Altogether range step is 4,00 and splitter step 1,20. In real auxiliaries HI-L is usually direct and HI-H overdrive. For more realistic lego ratios you can add Su(12)-XS(8) or M(24)-S(16) overdrive gear pair between auxiliary and main gearbox. This way you get ratios 4,00, 1,00 and 0,83 without changing gear steps. This sequential setup is simple and compact design with good efficiency. Only problem is difficult shift to HI-H due to S(16)-S(16) spur gear pair. If shifting problems become annoying available is also direct drive synchro setup with identical gear steps. So, low range ratio LO is 4,80 and in high range low split HI-L has ratio 1,20 and high split HI-H 1,00. This synchro version has two high-low shift levers: left one for splitter and right one for range change. This arrangement allows remote auxiliary shifting if you add mini motors to shift levers. But note in this design that splitter must be in low position to enable low range. This feature is copied from real Fuller’s auxiliary. B. Main Gearboxes: Geometrical gear steps Here is updated small collection of main gearboxes to be used in trucks and tractors. Largest number of gears in single manual gearbox is 7+R and that is not usually enough in truck and tractor transmissions. This will lead either too small overall gear ratio or too large gear steps so they use one or two auxiliary gearbox to multiply main gearbox’s number of gears. This way you will get also slow gears without too large gear steps. Auxiliaries also mean that you can’t use progressive gear steps or progression must be small. These lego designs are mainly with brick frame but in many cases studless frame should be possible. Mainly reverse gear’s S’(16C)-XS(8)-Su(12) gear train is problematic in studless frame. In some cases you can’t avoid old 14 teeth thin bevel gears or new 28 teeth gear without losing realistic ratios. B.1. Basic 5-speed synchromesh gearbox, overall gear ratio 9,00: Using examples: -5x4 & 5x3 twin stick
This 5-speed synchromesh gearbox is based on very simple gear pairs. Front and back movement of the shift lever handles between ratios 1,67 (done by 12 and 20 teeth gears) and 1,00 after the synchro parts. Shift lever’s left and right movement chooses between ratios 9,00, 3,00 and 1,00 before the synchro parts (done by 8 and 24 teeth gears). Altogether, gear steps are quite good but not optimal: they vary between 1,67 (gear steps 2-3 and 4-5) and 1,80 (gear step 1-2 and 3-4). All shiftings should have the same gear step value (or almost same) in transmission with geometrical gear steps.
This 5-speed main gearbox is simple but realistic auxiliaries for it is another job. Easiest design is to add 2-speed splitter with gear step 1,25-1,33. It’s simple lego design but ratio set is not realistic. For 5x4 and 5x3 twin stick transmissions this 5-speed main gearbox suits quite well. But auxiliaries of twin stick transmissions are more complex designs. So for realistic lego twin stick transmission you’ll need to check section N. Twin Stick Transmissions on main page. This gearbox has two alternative upgrade possibilities: 6-speed gearbox or 5-speed gearbox with a reverse gear. 6-speed gearbox has overall gear ratio 15,00 and it suits to 12-speed splitter-type truck transmission (6x2). Suitable splitter gear step is 1,25-1,33, but this lego design won’t have realistic ratio set. In real 12-speed splitter-type transmission splitter step is smaller and main gearbox has progressive gear steps. For basic lego design with splitter step 1,33 you can check L.2. 12-speed version IIA & IIB and for more realistic lego design O.8. 6-speed & 12-speed on main page. B.2. Basic 6-speed synchromesh gearbox, overall gear ratio 3,47: Using examples: -12+12R-speed tractor (6x2) -18+6R-speed & 24+6R-speed tractor (6x3 & 6x4)
This 6-speed gearbox is also basic version but it uses different gear pairs than previous 5-speed main gearbox. Now ratios before synchro parts are 1,00, 1,67 and 2,78 and they are done by 12 and 20 teeth gears. After synchro parts ratios are 1,00 and 1,25 which is done by 16 and 20 teeth gears. Gear step are not very good because they vary between 1,25 and 1,33. All in all gear steps are smaller so this main gearbox doesn’t need splitter but range-change unit.
This 6-speed design is for tractor use, in truck world 6-speed main gearbox with range-change unit is not used. So, in tractors 6-speed main gearbox can be used with 2-speed range unit and driving direction changer (shuttle). This gives 12+12R-speed design in which range gear step 4,00 is quite typical. Other use for 6-speed main gearbox are 18+6R-speed & 24+6R-speed tractors with 3+R-speed & 4+R-speed range units (ranges low, medium, high and reverse, additional creeper in 4+R-speed). In these designs ranges overlap heavily. For more info check T.5. 18+6R-speed & 24+6R-speed on main page. For truck world you will need modification: replace 1st gear with reverse gear to get 5-speed gearbox (overall gear ratio 2,78). It suits to 15-speed truck transmission (5x2+5) which has 10 road speeds in two ranges plus 5 deep reduction gears for low speed operating. More info about this is in section F. 15-speed Transmissions on main page. B.3. Basic 3+R-speed synchromesh gearbox, overall gear ratio 3,00: Using examples: -3+R-speed personal car -12-speed (2x3x2) -6+2R-speed tractor (3x2)
This basic 3+R-speed gearbox is a small brother of the earlier basic 5-speed synchromesh gearbox: 1st and 2nd gear are removed and reverse gear is added. Reverse gear adds some complexity for this design but it’s still as small as basic 4-speed. Available is two setups: in personal car/truck setup reverse gear is slower than 1st gear but in tractor setup faster. This difference is typical for real transmissions.
Gear step 1-2 is 1,80 and gear step 2-3 1,67 so this gearbox has actually progressive gear steps (the higher gear the smaller gear step between gears). So this gearbox suits straight to be used as old 3+R-speed personal car gearbox. In truck use this main gearbox will need both splitter and range-change unit which leads to 12-speed design (2x3x2). Suitable range gear step is 5,00 and suitable splitter steps are between 1,25-1,33. Larger splitter step leads to higher overall gear ratio but reduces gear step progression and performance in high speeds. My recommendation is splitter step 1,25 with stronger progression in gear steps, it gives overall gear ratio 18,75 which still suits very well to heavy duty trucks. In tractor transmissions range is not usually changed during driving. So range step is smaller than in truck use, or ranges can even overlap. For 6+2R-speed tractor with this main gearbox suits range unit with gear step 4,00. This design can be enlarged to 12+4R-speed version by adding Hi-Lo powershift. Typical powershift step will be around 1,33. B.4. 5+R-speed synchromesh gearbox, overall gear ratio 4,00: Using examples: -as 4+C+R-speed: heavy duty 13-speed & 18-speed (4x3+1 & 2x4x2+2) -as 4+R-speed: linehaul 16-speed (2x4x2) -as 5-speed: 15+15R-speed & 45+45R-speed tractor -as 4-speed: 8+4R-speed, 16+8R-speed & 12+8R-speed tractor
This 5+R-speed main gearbox is quite versatile design although it’s never used in its basic form. Available is two setups: old school setup has 14 teeth thin bevel gears with 20 teeth gear (ratio 1,43) and modern setup 20 teeth gear with new 28 teeth gear (ratio 1,40). These are for smaller gear step after synchro parts, front ratios 4,00, 2,00 and 1,00 are done by 8 and 16 teeth gears.
When you use this as 4-speed gearbox that has crawler (C) and reverse gear you can build heavy duty 13-speed and 18-speed truck transmissions. They have range-change unit and splitter but in 13-speed version splitter is available in high range only. And crawler gear is used in low range only. Suitable range gear step is 4,00 and splitter step 1,20. 13-speed version can use earlier 3-speed auxiliary that has compound splitter/range-change unit. When using as 4+R-speed design (no crawler gear) you can get linehaul 16-speed transmission. It uses same range and splitter steps as previous 13-speed and 18-speed. But you need some modifications in main gearbox: when removing crawler gear reverse gear becomes too slow. So I recommend to make reversing gear train XS(8)-XS(8)-XS(8) as front ratio between left and middle synchro axle and put reverse gear next to 1st gear. When using 5-speed design without reverse gear you can build 15+15R-speed and 45+45R-speed tractor transmissions. They have 3-speed range unit and driving direction changer (shuttle), 45+45R-speed version also 3-speed powershift. For more info you need to check 45+45R-speed designs on main page. When you remove crawler and reverse gear you can use 4-speed main gearbox in 8+4R-speed tractor transmission in which auxiliary has ranges high, low and reverse. And this 8+4R-speed design can be enlarged with Hi-Lo powershift (16+8R-speed), mechanical splitter (16+8R-speed) or creeper range (12+8R-speed). Suitable gear step for splitter is 1,20. For more info you need to check section S. Tractor Transmissions Part I on main page. And one note: if you build 16-speed and 18-speed without splitter you get 8-speed and 9-speed (4x2 & 4x2+1) truck transmissions. But quite large gear steps lead to bad performance in high speeds so they make top step 7-8 (and step 3-4 due to range-change unit) smaller than others. This helps to keep suitable engine rpm in all speed limits 50, 60, 70 and 80 km/h. In lego world this is not so big issue so you can use this main gearbox in 8-speed and 9-speed transmissions. B.5. 5+R-speed synchromesh gearbox, overall gear ratio 3,33: Using examples: -10-speed (5x2)
This 5-speed main gearbox is designed for 10-speed transmission with range-change unit. 10-speed transmission is quite simple and logical for truck transmission but realistic ratios lead to quite complex lego main gearbox.
Suitable range gear step for this main gearbox is 4,50. Combination gives overall gear ratio 15,00 which suits to linehaul and easier heavy duty purposes. So, this lego design is not the simplest but it gives simple and logical operating. Only reverse gear uses old 14 teeth thin bevel gears and this is for slightly slower reverse gear than 1st gear. If you don’t have those gear wheels you can copy reverse gear train S’(16C)-XS(8)-Su(12) from 3+R-speed main gearbox and transfer torque to output axle via S(16)-S(16)-S(16) gear train. B.6. 4+R-speed synchromesh gearbox, overall gear ratio 3,00: Using examples: -heavy duty 16-speed (2x4x2) -8+2R-speed tractor (4x2)
This 4+R-speed main gearbox is designed for heavy duty 16-speed transmission so it needs both splitter and range-change unit. Also this one is more complex design due to realistic ratio set. Suitable splitter gear step is 1,20 and suitable range step 4,50 or 4,29, the latter you get when you modify range-change unit with gear step 5,00.
Other use for this main gearbox is 8+2R-speed tractor in which range-change unit has gear step 4,00. Although reverse gear is already faster than 1st gear you can modify it as fast as 2nd gear when using this main gearbox in tractor. To get it use XS(8)-XS(8)-XS(8) gear train between middle and left synchro axle and keep reverse gear’s clutch gear next to 2nd gear. This ratio set is not possible without old 14 teeth thin bevel gears. If you have them you can build lego 16-speed transmission with very realistic ratios. If you have only new 28 teeth gear you can build 16-speed linehaul transmission with smaller overall gear ratio. For more info check 4+R-speed setup in chapter B.4. 5+R-speed synchromesh gearbox. B.7. Simple 2-speed synchromesh gearbox version A & B, gear step 1,71:
Here is simple 2-speed gearbox if you have only one transmission driving ring. In real automotive transmissions gear steps are usually under 2,00 because combustion engines are not good at handling large steps in shifting. So this lego transmission has ratio 12/7=1,71 in 1st gear and 1,00 in 2nd gear. Available is version A with brick frame and version B with studless frame. Transmission is quite simple to build but there are also building instructions available, check link BuildIt in Brickshelf Gallery or YouTube.
There are also two optional ratio sets available: When you replace 14 teeth bevel gears with 12 teeth gear you get ratio 2,00 for 1st gear. If you swap 14 teeth bevel gears and 12 teeth gear ratio of 1st gear will be 7/3=2,33. (If you replace this gear pair with 8 and 16 teeth gear pair you get synchromesh range-change unit with gear step 4,00.) As an other option you can make remote shifting system by adding small motor on shift lever axle. When you don’t use neutral position shift lever has only two positions and shift lever’s movement is limited with bricks. So you can do remotely simple up- and downshiftings between 1st and 2nd gear while driving. Actually this design is not a real main gearbox but ancient 2-speed personal car gearbox. But you can use this with splitter and range-change unit to get 8-speed transmission that has three Hi-Lo gearboxes. Suitable range gear step is 3,00 and splitter step 1,25-1,33. This kind of transmission doesn’t really exist but can be used as remote shiftable design with realistic ratios for lego playing. C. Transfer Cases: Transfer cases are used in off-road vehicles and they are needed for two reasons. They devide power to front and rear axle to get 4x4 design and with 2 speeds allow also low speed driving. Transfer case’s high (H) is for everyday use on the roads and low (L) is for off-road driving when low speeds are needed. C.1. Version I, gear step 2,25: With 5-speed version I This transfer case is together with 5-speed version I so check it on main page if you need more info about main gearbox. Transfer case is continuous 4WD with lockable centre differential so there are four options: H4 (high 4WD) and L4 (low 4WD) with centre differential in use or locked. High ratio is 2,00 and low ratio 4,50 so gear step is 2,25. Usually transfer case’s high ratio is direct but these ratios gave smaller construction with proper gear step. You can think this transfer case as part of final drive so you don’t need so large ratios in front and rear axle differentials.
C.2. Version II, gear step 2,25: With 5-speed version III Here is another transfer case for off-road vehicles and it’s together with 5-speed version III. Again transfer case’s high ratio is 2,00 and low ratio 4,50 so gear step is 2,25. This version II is updated version of previous transfer case version I and it has 5 options: H2 (high RWD) plus H4 (high 4WD) and L4 (low 4WD) with centre differential in use or locked.
This transmission uses original setup of 5-speed version III, check alternative setup or tutorial version for more compact and simpler main gearbox. C.3. Version III, gear step 2,40:
This is alternative setup for transfer case version III, original design P.17. Old 3-speed & transfer case version III is now on page Junkyard. This transfer case is old-fashioned two stick design: one stick for high and low selection and other one to switch front wheel drive on or off. High ratio is 1,25 and low ratio 3,00 so gear step of this transfer case is 2,40.
This design is part time 4x4 without centre differential so on the road and other good conditions it’s recommended to use only rear wheel drive. But when conditions get worse you can switch on front wheel drive and perhaps low selection if low speeds are needed. Available is also a remake for this type of two stick transfer case. For more information you can check P.17. 3-speed & transfer case version VI in section P. Personal Car Transmissions on main page. C.4. Version IV, gear step 2,50:
This is alternative parallel setup for transfer case version IV, original inline design was introduced in now junked 3-speed semiautomatic & transfer case version IV. This is another part time 4x4 design but it has one shift lever with three positions: H2 (high RWD), H4 (high 4WD) and L4 (low 4WD). So in good conditions you use rear wheel drive (H2) and in bad conditions high or low four wheel drive (H4 or L4). High ratio is 1,33 and low ratio 3,33 which gives gear step 2,50.
With 3-speed semiautomatic Inspirer: Ford Bronco II This is remake of 3-speed semiautomatic & transfer case version IV. It is based on off-road vehicle that has 3-speed automatic gearbox with torque converter and 2-speed part time 4x4 transfer case. In lego version 3-speed semiautomatic “main gearbox” is actually 2 motors and a planetary gear. For more information you can check B.8. 3-speed semiautomatic in Planetary gears.
In this remake transfer case’s low ratio is 2,50 and high ratio is direct 1,00, so gear step is still 2,50. Reason for this remake is more compact design. Original design was very space consuming and it’s moved to page Junkyard. C.5. Version V, gear step 2,25:
This transfer case version V uses smallest possible gear wheels so gearbox itself is very small design. But shift lever needs some more attention while there are not much places where to put it.
Again design is part time 4x4 and shift lever has three positions: H2 (high RWD), H4 (high 4WD) and L4 (low 4WD). So on the road you drive with rear wheel drive (H2) and four wheel drive positions H4 and L4 are for bad conditions only. This time high ratio is direct 1,00 and low ratio 2,25 so gear step is also 2,25. This transfer case has modified version together with P.8. 4-speed version III in section P. Personal Car Transmissions on main page. That 4-speeder is wide ratio design with typical ratio set of off-road vehicles so it’s logical to offer also additional lego transfer case.
D. Gearboxes With 2-speed Motor:
This Electric RC Race Buggy Motor has two outputs with gear step 23/17=1,35. If you have it you can take advantage of these outputs and use them both in one transmission. When used in splitter this gear step suits to 10-speed truck transmission. In main gearbox motor can be used so that two top gears use motor’s high output and lower gears low output. So, motor’s step 1,35 as second highest gear step gives several transmission possibilities: 10-speed with range-change unit for truck, 4-speed for muscle car, 5-speed for personal car, 6-speed for van and 7-speed for coach. D.1. 10-speed with splitter for truck, overall gear ratio 10,15: Splitter + main gearbox, also 12-speed conversion Inspirer: Scania GS771
This one is 10-speed transmission for mid range truck and 2-speed motor is used as splitter unit. Notable thing is that 8th and 9th gear are swapped in shift pattern. This swap gives halved gear steps in shifts 7-8, 8-9 and 9-10 and better performance in high speed driving. But swap also reduces overall gear ratio so this transmission doesn’t suit to heavy duty trucks.
This transmission is sister of M. 10-speed Transmission on main page. So if you don’t have this motor you can use this main gearbox directly with splitter unit of those transmissions on main page. It makes small changes in ratios and gear steps but not too much. On the other hand main gearboxes of those main page transmissions can be used with this motor-splitter. While this transmission is inspired by 10-speed Scania transmission I wanted 10 gears in lego transmission too. If you need more gears and larger overall gear ratio this transmission is easy convert into 12-speed version: just flip around 16 teeth clutch gear on the left synchro axle. Next pictures give you more info.
D.2. 10-speed version II B for truck, overall gear ratio 15,03: Main gearbox + range-change unit Inspirer: Eaton Fuller Advantage Series FA-10B
This one is 10-speed transmission for linehaul truck with 5-speed main gearbox and range-change unit. 2-speed motor used so that main gears 4-5 are from motor’s high output and gears 1-3 and reverse from low output. Main gearbox and range-change unit are parallel which gives quite short design so only space issue is width. This parallel design means also that there is a short cut in power flow in gears 8th and 9th between main gearbox’s and range-change unit’s clutch gears.
This lego transmission is only possible with studless frame due to used Su(12)-S(16) gear pairs. So there is exceptional 1,75 stud axle base in this transmission and it needs some careful axle locating if you build this version. Bushes should show to you where those special 0,25 stud gaps are needed. And reverse gear’s idler gear is slightly difficult to support in studless frame. Lego structure can be difficult to figure out from pictures so I recommend to download LDraw file or check YouTube clip Built it. One notable thing is gear order in shift pattern while main gearbox’s 4th and 5th gear are swapped. This swap gives easier use for motor’s gear step 1,35 but idea is taken from real Eaton’s transmissions: older 10-speed overdrive Fullers (RTO series) have same kind of swap. But these older 10-speed Fullers have smaller gear steps and overall gear ratio than this lego design and they are not suitable to model with this 2-speed lego motor. Lego version’s overdrive ratio set is close to newer Eaton Fuller Advantage Series FA-10B which is direct drive. Although ratios are all different gear steps and overall gear ratio are quite close to each other including larger range step 4-5. Reverse gear is also slower than 1st gear in main gearbox but lego version’s step -1,25 is a little bit larger than Fuller’s -1,18. Check similarities from picture Ratio comparison. But, there is a little reality issue while lego version’s shift pattern and ratio set are from different 10-speed Fuller models, but we can accept this small exception, can’t we. :-) More info about swapped gears in shift pattern is in chapter N.5. More about twin stick transmissions on main page. There is also sister design of this lego transmission with slightly different ratio set, check chapter I.5. 10-speed version V on main page. All in all this lego transmission is pretty realistic design for American linehaul semitrailer truck. Lego using idea goes so that you put motor and transmission partly under cabin but leave shift levers usable behind cabin. Then you put rear axles and fifth wheel rear enough so that semitrailer doesn’t hide shift levers. So there is still room for 6-cylinder inline engine in truck’s engine bay. D.3. 4-speed version B for muscle car, overall gear ratio 2,82: Inspirer: Borg Warner Super T-10 (X ratio) (Richmond Gear, present manufacturer) Progressive gear steps
This one is quite simple and compact 4-speed transmission for old American muscle cars and other sport cars. It’s inspired by X ratio set of Borg Warner Super T-10. 2-speed motor is used so that gears 3-4 uses motor’s high output and gears 1-2 low output so motor’s step 1,35 is between 2nd and 3rd gear.
All in all this gearbox has quite good progressive gear steps and overall gear ratio is typical for close ratio 4-speed sport cars. Progressive gear steps mean the higher gear the smaller gear step between gears. Note that progression in lego transmission is not optimized because it follows Borg Warner’s ratios and gear steps. If you want faster 1st gear (smaller gear step 1-2) you can do simple conversion: change rear 12 teeth double bevel gear to two 14 teeth thin bevel gears. And if you need ratios, gear steps and overall gear ratio of that conversion you can make request so I can calculate changed values with Excel. :-) Design has studless frame mainly because of studless motor but also brick frame is possible altough I haven’t modelled it. If you don’t have this 2-speed motor there is an ordinary sister transmission for this design, check original setup (X ratio) in chapter P.9. 4-speed version IV on main page. D.4. 5-speed version B for personal car, overall gear ratio 4,06: Progressive gear steps
Another use for this 2-speed motor is overdrive 5-speed personal car transmission. Gears 4-5 use motor’s high output and gears 1-3 low output. When 5th gear is overdrive and 4th gear direct motor’s gear step 1,35 can be used between gears 3 and 4. All in all this gearbox has very good progressive gear steps and overall gear ratio is typical for 5-speed personal car transmissions. H shift pattern is typical for light trucks and some sport cars but it’s easier to get progressive gear steps in lego gearbox with this arrangement. Progressive gear steps mean the higher gear the smaller gear step between gears.
Design has studless frame mainly because of studless motor but also brick frame is possible altough I haven’t modelled it. D.5. 6-speed version B for van, overall gear ratio 6,96: Inspirer: ZF Ecolite for van Progressive gear steps
In this 6-speed transmission overall gear ratio is too small for light trucks but too high for typical personal cars so transmission suits best for vans. Other possible use is wide ratio personal car transmission which are normally used in diesel powered cars.
In lego version gears 5-6 use motor’s high output and gears 1-4 low output. Motor’s gear step 1,35 is used in gear pair 4-5 while 5th gear is direct and 6th gear overdrive. Like in real 6-speed transmissions also this version has progressive gear steps which means the higher gear the smaller gear step between gears. This design is only possible with studless frame while there is horizontally located Mu(20)-S(16) gear pair in 2nd gear. This gear pair has unusual 2,25 stud axle base so put axle carefully into right place if you build this transmission. D.6. (reserved for 7-speed version B for coach) This is for 7-speed rear engine transmission for coach inspired by Eaton Fuller... E. Flat Gearbox Designs: Here are some flat transmissions where axles are in one or 1,5 layers. 1,5 layers mean that there is small vertical movement together with horizontal movement, but too small to put axles vertical. Designs are transversal and long but narrow so truck transmissions can be placed partly inside truck’s frame under cargo body. Shift levers are on the left side of the truck outside the frame. Also their height is minimized so it’s possible that they fit under cargo body too. In tractor use you can think that lego motor and front part of transmission is in tractor’s narrow engine bay and the rest under cabin. Here is how to make basic 8-speed transmission for mid range truck, small step 16-speed for linehaul truck and 14-speed for heavy duty truck. For tractor use here is basic 8+8R-speed and basic 8+4R-speed, that has two enlargements: 16+8R-speed with mechanical splitter and 12+8R-speed with creeper unit. E.1. Basic 8-speed for mid range truck, overall gear ratio 11,43: Range + main gearbox
This 8-speed transmission is basic design with 4-speed main gearbox and range-change unit. Instead of real 8-speed trucks gear steps are pure geometrical. Real 8-speed transmissions have normally smaller gear step 7-8 (also step 3-4 due to range-change unit) to get better performance in high speed driving. This is why this lego transmission doesn’t have inspirer. Lego transmission has large front ratio (6,00) from motor to range-change unit so this transmission suits to high speed motor. Shift lever in main gearbox allows only 4 positions so this transmission doesn’t have reverse gears.
This transmission is easy to enlarge to 16-speed version by adding splitter unit. Then you get small gear step transmission for linehaul truck. Or you can use 2 crown gears on 1st axle to get sliding axle driving direction changer so you will get 8+8R-speed tractor transmission. E.2. Small step 16-speed for linehaul truck, overall gear ratio 13,71: Splitter + range + main gearbox Inspirer: Volvo SR62
This 16-speed transmission has same type 4-speed main gearbox and range-change unit as previous 8-speeder. New feature is splitter unit which halves the gear steps and doubles the number of gears. Overall gear ratio is not very large so transmission suits to linehaul truck. While there is front ratio 3,00 and underdrive splitter this transmission works best with high speed motor. There are no reverse gears in this transmission so gears are: 1L-1H-2L-2H-3L-3H-4L-4H-5L-5H-6L-6H-7L-7H-8L-8H.
Best known real 16-speed transmission is ZF Ecosplit but it has larger overall gear ratio than this lego version. Now basic lego design lead to smaller overall gear ratio, so it and gear steps are closer to Volvo’s SR62 transmission. This is sister transmission of K.2. 16-speed transmission version II on main page. For lego heavy duty trucks I have 14-speed transmission which has larger gear steps and overall gear ratio. E.3. 14-speed for heavy duty truck, overall gear ratio 31,25: Range + splitter + main gearbox Inspirer: Volvo and Scania
This 14-speed transmission has 3-speed main gearbox including also crawler gear (C) together with splitter and range-change unit (2x3x2+2). Transmission has larger gear steps than previous 16-speeder so overall gear ratio is large and suitable for heavy and severe duty trucks. There is some progression in gear steps so step between highest gears is not so large as in transmission with geometrical gear steps. There are no reverse gears in this transmission so gears are: CL-CH-1L-1H-2L-2H-3L-3H-4L-4H-5L-5H-6L-6H.
This design is sister transmission of 14-speed versions I & II on main page. E.4. Basic 8+8R-speed for tractor, overall gear ratio 11,43: Fwd/rev + range + main gearbox Inspirer: Massey Ferguson 4220
This lego 8+8R-speed transmission is tractor version of earlier shown basic 8-speed truck transmission. Now there are two crown gears right next motor to get driving direction changer. Main gearbox is taken directly from that 8-speed but 16-speeder’s range-change unit suited better to this tractor design. Driving direction changer has ratio 2,00 so this design suits best to high speed motor.
E.5. Basic 8+4R-speed for tractor, overall gear ratio 11,43: Range/reverse + main gearbox Inspirer: Ford 6610 Dual-range
This 8+4R-speed transmission has same main gearbox as previous 8+8R-speed tractor and earlier basic 8-speed truck transmission. Now auxiliary has ranges low, high and reverse, so you have 4 slow and 4 fast gears in forward and 4 slow gears in reverse. This is direct drive version so it suits also to low speed motors. Unlike previous transmissions this one needs 1,5 layers.
This transmission is cousin of S.1. 8+4R-speed tractor transmission on main page with slightly different ratios in auxiliary. E.6. 16+8R-speed with splitter for tractor, overall gear ratio 13,71: Splitter + range/reverse + main gearbox Inspirer: Valmet 900
This 16+8R-speed transmission is enlarged version of previous 8+4R-speed tractor transmission. It contains same 4-speed main gearbox and range unit that has ranges high, low and reverse. New feature is mechanical splitter to enable more accurate working speed control. So this lego design is also close to earlier 16-speed truck transmission. This time lego design is overdrive so it suits best to low speed motor. Like 8+4R-speeder this transmission requires 1,5 layers.
When you look closely you can notice that this 16+8R-speed version has different inspirer than earlier 8+4R-speed version. This oddity comes from the fact that Ford offered only 2-speed powershift to enlarge 8+4R-speeder to 16+8R-speed version. On the other hand also Valmet had 8+4R-speed transmission and they offered mechanical splitter or creeper unit as optional equipment giving 16+8R-speed or 12+8R-speed versions. So this lego version follows that 16+8R-speed splitter version. This one has also cousin in S.3. 16+8R & 12+8R-speed tractor transmissions on main page with slightly different ratios in range unit. E.7. 12+8R-speed with creeper for tractor, overall gear ratio 45,71: Creeper + range/reverse + main gearbox Inspirer: Valmet 900
This 12+8R-speed transmission is another enlargement of earlier 8+4R-speed tractor transmission. So it’s based on 4-speed main gearbox and range unit with ranges high, low and reverse. Now additional equipment is creeper unit which can be switched on with ranges low and reverse. So it offers 4 extra slow gears in both driving directions giving 12 forward and 8 reverse gears altogether. This is direct drive version so it suits also to low speed motors and like 8+4R-speeder this transmission requires 1,5 layers.
If previous 16+8R-speed gives smaller gear steps this 12+8R-speed enables extra slow speeds. This one has also cousin in S.3. 16+8R & 12+8R-speed tractor transmissions on main page with slightly different ratios in range unit. F. Race Transmissions: Here are located transmissions that are designed for racing use. First three are drag race transmissions that have special lightning rod shifters to minimize shifting errors under maximum acceleration. Fourth one is 4-speed manual transmission for NASCAR racing with extremely close ratio design. F.1. 4-speed drag race version I, overall gear ratio 3,33: Inspirer: Lightning rod shifter
This design is 4-speed manual drag race transmission and it’s equipped with lightning rod shifter.
Lightning rod shifter means that you have three forward-rearward shift levers for three upshifts. Left one is for shift 1-2, middle one for shift 2-3 and right one for shift 3-4. You start with levers in front position and upshift by pulling levers rearward one at time starting from left lever. Check picture Shifting procedure. So it’s like three 2-speed gearboxes in a row. Idea is to minimize shifting errors under pressure in drag racing while shift levers have only two positions. Downshift happens in reversed order: while all levers are in rear position you downshift by pushing levers forward starting from right lever. I’m not drag race transmission specialist so I don’t know their typical gear steps and progression stage. Ratios of this lego version are taken from GM 4L80E 4-speed conventional automatic transmission which can be equipped with lightning rod shifter. One note is that GM 4L80E is overdrive transmission while lego version is direct drive but gear steps and overall gear ratio are close to each other. F.2. 4-speed drag race version II, overall gear ratio 2,86: Inspirer: Lightning rod shifter
This version II is another 4-speed manual drag race transmission with lightning rod shifter. This design has same gear step 3-4 as earlier version I but less progression so it reduces lower gear steps and overall gear ratio.
Check previous version I or picture Shifting procedure for how to operate lightning rod shifter. In this lego version ratios are taken from Borg Warner ST10 (CC Ratio) 4-speed manual transmission. F.3. 3-speed drag race, overall gear ratio 2,50: Inspirer: Lightning rod shifter
This one is compact 3-speed version of drag race transmissions that has lightning rod shifter.
Lego design is actually 4-speed version I without 4th gear and its smallest gear step. So you have only two shift levers: left one for shift 1-2 and right one for shift 2-3. You start with both levers in front position and upshift by pulling first left lever and then right lever rearward. Downshift happens reversed: first you push forward right lever and then left lever. This time lego ratios are taken from GM TH350 3-speed conventional automatic transmission which can be equipped with lightning rod shifter. F.4. 4-speed NASCAR, overall gear ratio 1,79:
If I understand it right older rules of NASCAR say that you have to use 3-4-speed manual H shift pattern transmission with next ratio limits: 1st gear ratio must be 1,70 or higher, 3rd gear ratio (2nd in 3-speed version) must be 1,14 or higher and top gear must have direct ratio. Other notable thing is that racing happens in high speeds on oval shaped tracks. So you don’t need fast acceleration in lower speeds which means that NASCAR transmissions are extremely close ratio versions. So overall gear ratio and gear steps are usually too small for normal 4-speed transmission, even for close ratio sport car.
Google search gave as real example ratios 1st 1,80, 2nd 1,45, 3rd 1,16 and 4th 1,00. These ratios are quite close to NASCAR’s ratio limits so it’s likely that also wider ratio sets are used. With legos I almost managed to copy these ratios including progressive gear steps: 1st 1,79, 2nd 1,43, 3rd 1,17 and 4th 1,00. Available is two lego setups with identical ratio set: original setup is shorter but wider while alternative setup is more narrow but longer. Lego setups differ only how 1st gear is arranged. So depending on your lego NASCAR design you have two setups which to choose more suitable. For other use than NASCAR these lego transmissions are useless due to too small overall gear ratio. This is also why these lego transmissions are here in race transmissions, not in section P. Personal Car Transmissions on main page.
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