AWTF-80 SC

The Aisin AW TF-8# SC series is a 6-speed automatic transmission designed for use in transverse engine applications produced by Aisin Seiki. It is built in Anjō, Japan,^[1] and is also called TF-80SC^[2] (AWF21), AF40-6, AM6,^[3] AW6A-EL and TF-81SC (AF21).^[4] All-wheel drive transfer cases can be fitted to the AWTF-80 SC.

It uses a Lepelletier gear mechanism,^[5] an epicyclic/planetary gearset, which can provide more gear ratios with significantly fewer components. This means the Aisin AW TF-8# SC series is actually lighter than its five-speed predecessors.

The Ford 6R, GM 6L, and ZF 6HP transmissions are based on the same globally patented gearset concept. The AWTF-80 SC is the only one for transverse engine installation.

The main objective in replacing the predecessor model was to improve vehicle fuel economy with extra speeds and a wider gear span to allow the engine speed level to be lowered (downspeeding). The layout brings the ability to shift in a non-sequential manner – going from gear 6 to gear 2 in extreme situations simply by changing one shift element (actuating clutch E and releasing brake A).

In order to increase the number of ratios, ZF has abandoned the conventional design method of limiting themselves to pure in-line epicyclic gearing and extended it to a combination with parallel epicyclic gearing. This was only possible thanks to computer-aided design and has resulted in a globally patent for this gearset concept. The AWTF-80 is based on the 6HP from ZF, which was the first transmission designed according to this new paradigm. After gaining additional gear ratios only with additional components, this time the number of components has to decrease while the number of ratios still increase. The progress is reflected in a much better ratio of the number of gears to the number of components used compared to existing layouts.

Gearset Concept: Cost-Effectiveness^[a]

With Assessment	Output: Gear Ratios	Innovation Elasticity[b] Δ Output :  Δ Input	Input: Main Components
			Total	Gearsets	Brakes	Clutches
AWTF-80 Ref. Object	${\displaystyle n_{O1}}$ ${\displaystyle n_{O2}}$	Topic[b]	${\displaystyle n_{I}=n_{G}+}$ ${\displaystyle n_{B}+n_{C}}$	${\displaystyle n_{G1}}$ ${\displaystyle n_{G2}}$	${\displaystyle n_{B1}}$ ${\displaystyle n_{B2}}$	${\displaystyle n_{C1}}$ ${\displaystyle n_{C2}}$
Δ Number	${\displaystyle n_{O1}-n_{O2}}$		${\displaystyle n_{I1}-n_{I2}}$	${\displaystyle n_{G1}-n_{G2}}$	${\displaystyle n_{B1}-n_{B2}}$	${\displaystyle n_{C1}-n_{C2}}$
Relative Δ	Δ Output ${\displaystyle {\tfrac {n_{O1}-n_{O2}}{n_{O2}}}}$	${\displaystyle {\tfrac {n_{O1}-n_{O2}}{n_{O2}}}:{\tfrac {n_{I1}-n_{I2}}{n_{I2}}}}$ ${\displaystyle ={\tfrac {n_{O1}-n_{O2}}{n_{O2}}}}$·${\displaystyle {\tfrac {n_{I2}}{n_{I1}-n_{I2}}}}$	Δ Input ${\displaystyle {\tfrac {n_{I1}-n_{I2}}{n_{I2}}}}$	${\displaystyle {\tfrac {n_{G1}-n_{G2}}{n_{G2}}}}$	${\displaystyle {\tfrac {n_{B1}-n_{B2}}{n_{B2}}}}$	${\displaystyle {\tfrac {n_{C1}-n_{C2}}{n_{C2}}}}$
AWTF-80 Aisin TB-50LS[c]	6[d] 5[d]	Progress[b]	8 9	3[e] 3	2 3	3 3
Δ Number	1		-1	0	-1	0
Relative Δ	0.200 ${\displaystyle {\tfrac {1}{5}}}$	−1.800[b] ${\displaystyle {\tfrac {1}{5}}:{\tfrac {-1}{9}}={\tfrac {1}{5}}}$·${\displaystyle {\tfrac {-9}{1}}={\tfrac {-9}{5}}}$	−0.111 ${\displaystyle {\tfrac {-1}{9}}}$	0.000 ${\displaystyle {\tfrac {0}{3}}}$	−0.333 ${\displaystyle {\tfrac {-1}{3}}}$	0.000 ${\displaystyle {\tfrac {0}{3}}}$
AWTF-80 3-Speed[f]	6[d] 3[d]	Market Position[b]	8 7	3[e] 2	2 3	3 2
Δ Number	3		1	1	-1	1
Relative Δ	1.000 ${\displaystyle {\tfrac {1}{1}}}$	7.000[b] ${\displaystyle {\tfrac {1}{1}}:{\tfrac {1}{7}}={\tfrac {1}{1}}}$·${\displaystyle {\tfrac {7}{1}}={\tfrac {7}{1}}}$	0.143 ${\displaystyle {\tfrac {1}{7}}}$	0.500 ${\displaystyle {\tfrac {1}{2}}}$	−0.333 ${\displaystyle {\tfrac {-1}{3}}}$	0.500 ${\displaystyle {\tfrac {1}{2}}}$
^ Progress increases cost-effectiveness and is reflected in the ratio of forward gears to main components. It depends on the power flow: parallel: using the two degrees of freedom of planetary gearsets to increase the number of gears with unchanged number of components serial: in-line combined planetary gearsets without using the two degrees of freedom to increase the number of gears a corresponding increase in the number of components is unavoidable ^ a b c d e f Innovation Elasticity Classifies Progress And Market Position Automobile manufacturers drive forward technical developments primarily in order to remain competitive or to achieve or defend technological leadership. This technical progress has therefore always been subject to economic constraints Only innovations whose relative additional benefit is greater than the relative additional resource input, i.e. whose economic elasticity is greater than 1, are considered for realization The required innovation elasticity of an automobile manufacturer depends on its expected return on investment. The basic assumption that the relative additional benefit must be at least twice as high as the relative additional resource input helps with orientation negative, if the output increases and the input decreases, is perfect 2 or above is good 1 or above is acceptable (red) below this is unsatisfactory (bold) ^ Direct Predecessor To reflect the progress of the specific model change ^ a b c d plus 1 reverse gear ^ a b of which 2 gearsets are combined as a compound Ravigneaux gearset ^ Reference Standard (Benchmark) 3-speed transmissions with torque converters have established the modern market for automatic transmissions and thus made it possible in the first place, as this design proved to be a particularly successful compromise between cost and performance It became the archetype and dominated the world market for around 3 decades, setting the standard for automatic transmissions. It was only when fuel consumption became the focus of interest that this design reached its limits, which is why it has now completely disappeared from the market What has remained is the orientation that it offers as a reference standard (point of reference, benchmark) for this market for determining progressiveness and thus the market position of all other, later designs All transmission variants consist of 7 main components Typical examples are Turbo-Hydramatic from GM Cruise-O-Matic from Ford TorqueFlite from Chrysler Detroit Gear from BorgWarner for Studebaker BW-35 from BorgWarner and as T35 from Aisin 3N 71 from Nissan/Jatco 3 HP from ZF Friedrichshafen W3A 040 and W3B 050 from Mercedes-Benz

To reduce external wiring as well as to provide a constant environment for the transmission control module (TCM), it is located inside the transmission housing. Gear shifting is managed by a computer program that oversees a clutch-to-clutch actuation that allows one clutch engage the instant the clutch from the previous gear disengages. When idling and with the foot brake depressed neutral gear is selected automatically. This helps to reduce internal temperatures and improve the fuel economy.

A conventional 5-pinion planetary gearset and a compound Ravigneaux gearset is combined in a Lepelletier gear mechanism,^[5] to reduce both the size and weight. It was first realized in 2000 with the 6HP from ZF Friedrichshafen. Like all transmissions realized with Lepelletier transmissions, the AWTF-80 SC also dispenses with the use of the direct gear ratio, making it one of the very few automatic transmission concepts without such a ratio.

It also has the capability to achieve torque converter lock-up on all 6 forward gears, and disengage it completely when at a standstill, significantly closing the fuel efficiency gap between automatic and manual transmissions.

The ratios of the 6 gears are evenly distributed in all versions. Exceptions are the large step from 1st to 2nd gear and the almost geometric steps from 3rd to 4th to 5th gear. They cannot be eliminated without affecting all other gears. As the large step is shifted due to the large span to a lower speed range than with conventional gearboxes, it is less significant. As the gear steps are smaller overall due to the additional gear(s), the geometric gear steps are still smaller than the corresponding gear steps of conventional gearboxes. Overall, therefore, the weaknesses are not overly significant. As the selected gearset concept saves up to 2 components compared to 5-speed transmissions, the advantages clearly outweigh the disadvantages.

In a Lepelletier gearset,^[5] a conventional planetary gearset and a composite Ravigneaux gearset are combined to reduce both the size and weight as well as the manufacturing costs. Like all transmissions realized with Lepelletier transmissions, the 6L also dispenses with the use of the direct gear ratio and is thus one of the very few automatic transmission concepts without such a ratio.

Gear Ratio Analysis

In-Depth Analysis With Assessment[a][b][c]		Planetary Gearset: Teeth[d] Lepelletier Gear Mechanism			Count	Nomi- nal[e] Effec- tive[f]	Cen- ter[g]
		Simple	Ravigneaux				Avg.[h]
Model	Version First Delivery	S1[i] R1[j]	S2[k] R2[l]	S3[m] R3[n]	Brakes Clutches	Ratio Span	Gear Step[o]
Gear Ratio	R ${\displaystyle {i_{R}}}$	1 ${\displaystyle {i_{1}}}$	2 ${\displaystyle {i_{2}}}$	3 ${\displaystyle {i_{3}}}$	4 ${\displaystyle {i_{4}}}$	5 ${\displaystyle {i_{5}}}$	6 ${\displaystyle {i_{6}}}$
Step[o]	${\displaystyle -{\frac {i_{R}}{i_{1}}}}$[p]	${\displaystyle {\frac {i_{1}}{i_{1}}}}$	${\displaystyle {\frac {i_{1}}{i_{2}}}}$[q]	${\displaystyle {\frac {i_{2}}{i_{3}}}}$	${\displaystyle {\frac {i_{3}}{i_{4}}}}$	${\displaystyle {\frac {i_{4}}{i_{5}}}}$	${\displaystyle {\frac {i_{5}}{i_{6}}}}$
Δ Step[r][s]			${\displaystyle {\tfrac {i_{1}}{i_{2}}}:{\tfrac {i_{2}}{i_{3}}}}$	${\displaystyle {\tfrac {i_{2}}{i_{3}}}:{\tfrac {i_{3}}{i_{4}}}}$	${\displaystyle {\tfrac {i_{3}}{i_{4}}}:{\tfrac {i_{4}}{i_{5}}}}$	${\displaystyle {\tfrac {i_{4}}{i_{5}}}:{\tfrac {i_{5}}{i_{6}}}}$
Shaft Speed	${\displaystyle {\frac {i_{1}}{i_{R}}}}$	${\displaystyle {\frac {i_{1}}{i_{1}}}}$	${\displaystyle {\frac {i_{1}}{i_{2}}}}$	${\displaystyle {\frac {i_{1}}{i_{3}}}}$	${\displaystyle {\frac {i_{1}}{i_{4}}}}$	${\displaystyle {\frac {i_{1}}{i_{5}}}}$	${\displaystyle {\frac {i_{1}}{i_{6}}}}$
Δ Shaft Speed[t]	${\displaystyle 0-{\tfrac {i_{1}}{i_{R}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{1}}}-0}$	${\displaystyle {\tfrac {i_{1}}{i_{2}}}-{\tfrac {i_{1}}{i_{1}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{3}}}-{\tfrac {i_{1}}{i_{2}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{4}}}-{\tfrac {i_{1}}{i_{3}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{5}}}-{\tfrac {i_{1}}{i_{4}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{6}}}-{\tfrac {i_{1}}{i_{5}}}}$
Specific Torque[u]	${\displaystyle {\tfrac {T_{2;R}}{T_{1;R}}}}$[v]	${\displaystyle {\tfrac {T_{2;1}}{T_{1;1}}}}$[v]	${\displaystyle {\tfrac {T_{2;2}}{T_{1;2}}}}$[v]	${\displaystyle {\tfrac {T_{2;3}}{T_{1;3}}}}$[v]	${\displaystyle {\tfrac {T_{2;4}}{T_{1;4}}}}$[v]	${\displaystyle {\tfrac {T_{2;5}}{T_{1;5}}}}$[v]	${\displaystyle {\tfrac {T_{2;6}}{T_{1;6}}}}$[v]
Efficiency ${\displaystyle \eta _{n}}$[u]	${\displaystyle {\tfrac {T_{2;R}}{T_{1;R}}}:{i_{R}}}$	${\displaystyle {\tfrac {T_{2;1}}{T_{1;1}}}:{i_{1}}}$	${\displaystyle {\tfrac {T_{2;2}}{T_{1;2}}}:{i_{2}}}$	${\displaystyle {\tfrac {T_{2;3}}{T_{1;3}}}:{i_{3}}}$	${\displaystyle {\tfrac {T_{2;4}}{T_{1;4}}}:{i_{4}}}$	${\displaystyle {\tfrac {T_{2;5}}{T_{1;5}}}:{i_{5}}}$	${\displaystyle {\tfrac {T_{2;6}}{T_{1;6}}}:{i_{6}}}$
Aisin AWTF-80 SC	450 N⋅m (332 lb⋅ft) 2005[6]	50 90	36 44	44 96	2 3	6.0494 4.9495 [f][p]	1.6865
							1.4333[o]
Gear Ratio	−3.3939[p][f] ${\displaystyle -{\tfrac {112}{33}}}$	4.1481 ${\displaystyle {\tfrac {112}{27}}}$	2.3704[q] ${\displaystyle {\tfrac {64}{27}}}$	1.5556 ${\displaystyle {\tfrac {14}{9}}}$	1.1546[s] ${\displaystyle {\tfrac {112}{97}}}$	0.8593 ${\displaystyle {\tfrac {336}{391}}}$	0.6857[t] ${\displaystyle {\tfrac {24}{35}}}$
Step	0.8182[p]	1.0000	1.7500[q]	1.5238	1.3472	1.3436	1.2532
Δ Step[r]			1.1484	1.1311	1.0027[s]	1.0722
Speed	-1.2222	1.0000	1.7500	2.6667	3.5926	4.8272	6.0494
Δ Speed	1.2222	1.0000	0.7500	0.9167	0.9259	1.2346	1.2222[t]
Specific Torque[u]	–3.3023 –3.2568	3.9956 3.9204	2.3127 2.2841	1.5444 1.5389	1.1471 1.1434	0.8553 0.8532	0.6813 0.6791
Efficiency ${\displaystyle \eta _{n}}$[u]	0.9730 0.9596	0.9632 0.9451	0.9757 0.9636	0.9929 0.9893	0.9935 0.9903	0.9953 0.9928	0.9936 0.9904
ZF 6HP	All[c] · 2000[w]	37 71	31 38	38 85	2 3	6.0354 4.9236 [f][p]	1.6977
							1.4327[o]
Gear Ratio	−3.4025[p][f] ${\displaystyle -{\tfrac {4,590}{1,349}}}$	4.1708 ${\displaystyle {\tfrac {9,180}{2,201}}}$	2.3397[q] ${\displaystyle {\tfrac {211,140}{90,241}}}$	1.5211 ${\displaystyle {\tfrac {108}{71}}}$	1.1428 [s][t] ${\displaystyle {\tfrac {9,180}{8,033}}}$	0.8672 ${\displaystyle {\tfrac {4,590}{5,293}}}$	0.6911 ${\displaystyle {\tfrac {85}{123}}}$
Step	0.8158[p]	1.0000	1.7826[q]	1.5382	1.3311	1.3178	1.2549
Δ Step[r]			1.1589	1.1559	1.0101[s]	1.0502
Speed	-1.2258	1.0000	1.7826	2.7419	3.6497	4.8096	6.0354
Δ Speed	1.2258	1.0000	0.7826	0.9593	0.9078[t]	1.1599	1.2258
Specific Torque[u]	–3.3116 –3.2665	4.0186 3.9436	2.2837 2.2559	1.5107 1.5055	1.1359 1.1325	0.8633 0.8613	0.6867 0.6845
Efficiency ${\displaystyle \eta _{n}}$[u]	0.9733 0.9600	0.9635 0.9455	0.9761 0.9642	0.9931 0.9897	0.9939 0.9910	0.9955 0.9932	0.9937 0.9905
Actuated Shift Elements
Brake A[x]		❶	❶	❶	❶
Brake B[y]	❶			❶		❶
Clutch C[z]			❶				❶
Clutch D[aa]	❶	❶
Clutch E[ab]					❶	❶	❶
Geometric Ratios
Ratio R & 3 & 6 Ordinary[ac] Elementary Noted[ad]	${\displaystyle i_{R}=-{\frac {R_{3}(S_{1}+R_{1})}{R_{1}S_{3}}}}$		${\displaystyle i_{3}={\frac {S_{1}+R_{1}}{R_{1}}}}$		${\displaystyle i_{6}={\frac {R_{3}}{S_{3}+R_{3}}}}$
	${\displaystyle i_{R}=-\left(1+{\tfrac {S_{1}}{R_{1}}}\right){\tfrac {R_{3}}{S_{3}}}}$		${\displaystyle i_{3}=1+{\tfrac {S_{1}}{R_{1}}}}$		${\displaystyle i_{6}={\tfrac {1}{1+{\tfrac {S_{3}}{R_{3}}}}}}$
Ratio 1 & 2 Ordinary[ac] Elementary Noted[ad]	${\displaystyle i_{1}={\frac {R_{2}R_{3}(S_{1}+R_{1})}{R_{1}S_{2}S_{3}}}}$			${\displaystyle i_{2}={\frac {R_{3}(S_{1}+R_{1})(S_{2}+R_{2})}{R_{1}S_{2}(S_{3}+R_{3})}}}$
	${\displaystyle i_{1}=\left(1+{\tfrac {S_{1}}{R_{1}}}\right){\tfrac {R_{2}R_{3}}{S_{2}S_{3}}}}$			${\displaystyle i_{2}={\tfrac {\left(1+{\tfrac {S_{1}}{R_{1}}}\right)\left(1+{\tfrac {R_{2}}{S_{2}}}\right)}{1+{\tfrac {S_{3}}{R_{3}}}}}}$
Ratio 4 & 5 Ordinary[ac] Elementary Noted[ad]	${\displaystyle i_{4}={\frac {R_{2}R_{3}(S_{1}+R_{1})}{R_{2}R_{3}(S_{1}+R_{1})-S_{1}S_{2}S_{3}}}}$			${\displaystyle i_{5}={\frac {R_{3}(S_{1}+R_{1})}{R_{3}(S_{1}+R_{1})+S_{1}S_{3}}}}$
	${\displaystyle i_{4}={\tfrac {1}{1-{\tfrac {\tfrac {S_{2}S_{3}}{R_{2}R_{3}}}{1+{\tfrac {R_{1}}{S_{1}}}}}}}}$			${\displaystyle i_{5}={\tfrac {1}{1+{\tfrac {\tfrac {S_{3}}{R_{3}}}{1+{\tfrac {R_{1}}{S_{1}}}}}}}}$
Kinetic Ratios
Specific Torque[u] R & 3 & 6	${\displaystyle {\tfrac {T_{2;R}}{T_{1;R}}}=-\left(1+{\tfrac {S_{1}}{R_{1}}}\eta _{0}\right){\tfrac {R_{3}}{S_{3}}}\eta _{0}}$		${\displaystyle {\tfrac {T_{2;3}}{T_{1;3}}}=1+{\tfrac {S_{1}}{R_{1}}}\eta _{0}}$		${\displaystyle {\tfrac {T_{2;6}}{T_{1;6}}}={\tfrac {1}{1+{\tfrac {S_{3}}{R_{3}}}\cdot {\tfrac {1}{\eta _{0}}}}}}$
Specific Torque[u] 1 & 2	${\displaystyle {\tfrac {T_{2;1}}{T_{1;1}}}=\left(1+{\tfrac {S_{1}}{R_{1}}}\eta _{0}\right){\tfrac {R_{2}R_{3}}{S_{2}S_{3}}}{\eta _{0}}^{\tfrac {3}{2}}}$			${\displaystyle {\tfrac {T_{2;2}}{T_{1;2}}}={\tfrac {\left(1+{\tfrac {S_{1}}{R_{1}}}\eta _{0}\right)\left(1+{\tfrac {R_{2}}{S_{2}}}\eta _{0}\right)}{1+{\tfrac {S_{3}}{R_{3}}}\cdot {\tfrac {1}{\eta _{0}}}}}}$
Specific Torque[u] 4 & 5	${\displaystyle {\tfrac {T_{2;4}}{T_{1;4}}}={\tfrac {1}{1-{\tfrac {{\tfrac {S_{2}S_{3}}{R_{2}R_{3}}}{\eta _{0}}^{\tfrac {3}{2}}}{1+{\tfrac {R_{1}}{S_{1}}}\cdot {\tfrac {1}{\eta _{0}}}}}}}}$			${\displaystyle {\tfrac {T_{2;5}}{T_{1;5}}}={\tfrac {1}{1+{\tfrac {{\tfrac {S_{3}}{R_{3}}}\cdot {\tfrac {1}{\eta _{0}}}}{1+{\tfrac {R_{1}}{S_{1}}}\eta _{0}}}}}}$
^ Revised 16 November 2025 ^ The AWTF80 SC-transmission is based on the Lepelletier gear mechanism, first realized in the ZF 6HP gearbox ^ a b Other gearboxes using the Lepelletier gear mechanism see infobox ^ Layout Input and output are on opposite sides Planetary gearset 1 is on the input (turbine) side Input shafts are R1 and, if actuated, C2/C3 (the combined carrier of the compound Ravigneaux gearset 2 and 3) Output shaft is R3 (ring gear of gearset 3: outer Ravigneaux gearset) ^ Total Ratio Span (Total Gear/Transmission Ratio) Nominal ${\displaystyle {\frac {i_{1}}{i_{n}}}}$ A wider span enables the downspeeding when driving outside the city limits increase the climbing ability when driving over mountain passes or off-road or when towing a trailer ^ a b c d e Total Ratio Span (Total Gear/Transmission Ratio) Effective ${\displaystyle {\frac {min(i_{1};|i_{R}|)}{i_{n}}}}$ The span is only effective to the extent that the reverse gear ratio matches that of 1st gear see also Standard R:1 ^ Ratio Span's Center ${\displaystyle (i_{1}i_{n})^{\frac {1}{2}}}$ The center indicates the speed level of the transmission Together with the final drive ratio it gives the shaft speed level of the vehicle ^ Average Gear Step ${\displaystyle \left({\frac {i_{1}}{i_{n}}}\right)^{\frac {1}{n-1}}}$ With decreasing step width the gears connect better to each other shifting comfort increases ^ Sun 1: sun gear of gearset 1 ^ Ring 1: ring gear of gearset 1 ^ Sun 2: sun gear of gearset 2: inner Ravigneaux gearset ^ Ring 2: ring gear of gearset 2: inner Ravigneaux gearset ^ Sun 3: sun gear of gearset 3: outer Ravigneaux gearset ^ Ring 3: ring gear of gearset 3: outer Ravigneaux gearset ^ a b c d Standard 50:50 — 50 % Is Above And 50 % Is Below The Average Gear Step — With steadily decreasing gear steps (yellow highlighted line Step) and a particularly large step from 1st to 2nd gear the lower half of the gear steps (between the small gears; rounded down, here the first 2) is always larger and the upper half of the gear steps (between the large gears; rounded up, here the last 3) is always smaller than the average gear step (cell highlighted yellow two rows above on the far right) lower half: smaller gear steps are a waste of possible ratios (red bold) upper half: larger gear steps are unsatisfactory (red bold) ^ a b c d e f g Standard R:1 — Reverse And 1st Gear Have The Same Ratio — The ideal reverse gear has the same transmission ratio as 1st gear no impairment when maneuvering especially when towing a trailer a torque converter can only partially compensate for this deficiency Plus 11.11 % minus 10 % compared to 1st gear is good Plus 25 % minus 20 % is acceptable (red) Above this is unsatisfactory (bold) see also Total Ratio Span (Total Gear/Transmission Ratio) Effective ^ a b c d e Standard 1:2 — Gear Step 1st To 2nd Gear As Small As Possible — With continuously decreasing gear steps (yellow marked line Step) the largest gear step is the one from 1st to 2nd gear, which for a good speed connection and a smooth gear shift must be as small as possible A gear ratio of up to 1.6667 : 1 (5 : 3) is good Up to 1.7500 : 1 (7 : 4) is acceptable (red) Above is unsatisfactory (bold) ^ a b c From large to small gears (from right to left) ^ a b c d e Standard STEP — From Large To Small Gears: Steady And Progressive Increase In Gear Steps — Gear steps should increase: Δ Step (first green highlighted line Δ Step) is always greater than 1 As progressive as possible: Δ Step is always greater than the previous step Not progressively increasing is acceptable (red) Not increasing is unsatisfactory (bold) ^ a b c d e Standard SPEED — From Small To Large Gears: Steady Increase In Shaft Speed Difference — Shaft speed differences should increase: Δ Shaft Speed (second line marked in green Δ (Shaft) Speed) is always greater than the previous one 1 difference smaller than the previous one is acceptable (red) 2 consecutive ones are a waste of possible ratios (bold) ^ a b c d e f g h i Specific Torque Ratio And Efficiency The specific torque is the Ratio of output torque ${\displaystyle T_{2;n}}$ to input torque ${\displaystyle T_{1;n}}$ with ${\displaystyle n=gear}$ The efficiency is calculated from the specific torque in relation to the transmission ratio Power loss for single meshing gears is in the range of 1 % to 1.5 % helical gear pairs, which are used to reduce noise in passenger cars, are in the upper part of the loss range spur gear pairs, which are limited to commercial vehicles due to their poorer noise comfort, are in the lower part of the loss range ^ a b c d e f g Corridor for specific torque and efficiency in planetary gearsets, the stationary gear ratio ${\displaystyle i_{0}}$ is formed via the planetary gears and thus by two meshes for reasons of simplification, the efficiency for both meshes together is commonly specified there the efficiencies ${\displaystyle \eta _{0}}$ specified here are based on assumed efficiencies for the stationary ratio ${\displaystyle i_{0}}$ of ${\displaystyle \eta _{0}=0.9800}$ (upper value) and ${\displaystyle \eta _{0}=0.9700}$ (lower value) for both interventions together The corresponding efficiency for single-meshing gear pairs is ${\displaystyle {\eta _{0}}^{\tfrac {1}{2}}}$ at ${\displaystyle 0.9800^{\tfrac {1}{2}}=0.98995}$ (upper value) and ${\displaystyle 0.9700^{\tfrac {1}{2}}=0.98489}$ (lower value) ^ First gearbox on the market to use the Lepelletier gear mechanism for comparison purposes only ^ Blocks R2 and S3 ^ Blocks C2 (carrier 2) and C3 (carrier 3) ^ Couples C1 (carrier 1) and S2 ^ Couples C1 (carrier 1) with R2 and S3 ^ Couples R1 with C2 (carrier 2) and C3 (carrier 3) ^ a b c Ordinary Noted For direct determination of the ratio ^ a b c Elementary Noted Alternative representation for determining the transmission ratio Contains only operands With simple fractions of both central gears of a planetary gearset Or with the value 1 As a basis For reliable And traceable Determination of specific torque and efficiency