6HP
Automatic Transmission 6HP 26 cutaway
Overview
Manufacturer	ZF Friedrichshafen
Production	2000–2014
Model years	2000–2014
Body and chassis
Class	6-SpeedLongitudinalAutomatic Transmission
Related	Ford 6R GM 6L Aisin AWTF-80 SC MB 7G-Tronic
Dimensions
Curb weight	72–99 kg (159–218 lb)[1]
Chronology
Predecessor	ZF 5HP
Successor	ZF 8HP

6HP isZF Friedrichshafen AG'strademark name for its 6-speedautomatic transmission models (6-speed transmission withHydraulic converter andPlanetary gearsets) forlongitudinal engine applications, designed and built by ZF's subsidiary inSaarbrücken. Released as the6HP 26 in 2000, it was the first 6-speed automatic transmission in a production passengercar. Other variations of the first generation6HP in addition to the6HP 26, were6HP19, and6HP 32 having lower and higher torque capacity, respectively. In 2007, the second generation of the6HP series was introduced, with models6HP 21 and6HP 28. A6HP 34 was planned, but never went into production.^[2]

It uses theLepelletier gear mechanism,^[3] anepicyclic/planetary gearset, which can provide more gear ratios with significantly fewer components. This means the6HP 26 is actually lighter than its five-speed5HP predecessors. The6HP is the first transmission to use theLepelletier gear mechanism.

The last6HP automatic transmission was produced by the Saarbrücken plant in March 2014 after 7,050,232 units were produced.^[4][5] The ZF plant in Shanghai continued to produce the6HP for the Chinese market.^[4]

TheFord 6R,GM 6L, andAisin AWTF-80 SC transmissions are all based on the same globally patentedLepelletier gear mechanism. TheAWTF-80 SC is the only one fortransverse 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-lineepicyclic gearing and extended it to a combination with parallelepicyclic gearing. This was only possible thanks to computer-aided design and has resulted in a global patent for this gearset concept. The6HP is 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
6HP 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 ${\displaystyle \frac{n_{O1}-n_{O2}}{n_{O2}}}$	${\displaystyle \frac{n_{O1}-n_{O2}}{n_{O2}}:\frac{n_{I1}-n_{I2}}{n_{I2}}}$ ${\displaystyle =\frac{n_{O1}-n_{O2}}{n_{O2}}}$·${\displaystyle \frac{n_{I2}}{n_{I1}-n_{I2}}}$	Δ Input ${\displaystyle \frac{n_{I1}-n_{I2}}{n_{I2}}}$	${\displaystyle \frac{n_{G1}-n_{G2}}{n_{G2}}}$	${\displaystyle \frac{n_{B1}-n_{B2}}{n_{B2}}}$	${\displaystyle \frac{n_{C1}-n_{C2}}{n_{C2}}}$
6HP 5HP 24/30[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 ${\displaystyle \frac{1}{5}}$	−1.800[b] ${\displaystyle \frac{1}{5}:\frac{-1}{9}=\frac{1}{5}}$·${\displaystyle \frac{-9}{1}=\frac{-9}{5}}$	−0.111 ${\displaystyle \frac{-1}{9}}$	0.000 ${\displaystyle \frac{0}{3}}$	−0.333 ${\displaystyle \frac{-1}{3}}$	0.000 ${\displaystyle \frac{0}{3}}$
6HP 5HP 18/19[c]	6[d] 5[d]	Progress[b]	8 10	3[e] 3[e]	2 3	3 4
Δ Number	1		-2	0	-1	-1
Relative Δ	0.200 ${\displaystyle \frac{1}{5}}$	−1.000[b] ${\displaystyle \frac{1}{5}:\frac{-1}{5}=\frac{1}{5}}$·${\displaystyle \frac{-5}{1}=\frac{-1}{1}}$	−0.200 ${\displaystyle \frac{-1}{5}}$	0.000 ${\displaystyle \frac{0}{3}}$	−0.333 ${\displaystyle \frac{-1}{3}}$	−0.250 ${\displaystyle \frac{-1}{4}}$
6HP 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 ${\displaystyle \frac{1}{1}}$	7.000[b] ${\displaystyle \frac{1}{1}:\frac{1}{7}=\frac{1}{1}}$·${\displaystyle \frac{7}{1}=\frac{7}{1}}$	0.143 ${\displaystyle \frac{1}{7}}$	0.500 ${\displaystyle \frac{1}{2}}$	−0.333 ${\displaystyle \frac{-1}{3}}$	0.500 ${\displaystyle \frac{1}{2}}$
^Progress increases cost-effectiveness and is reflected in theratio of forward gears to main components. It depends on thepower flow: parallel: using the two degrees of freedom ofplanetary gearsets to increase the number of gears with unchanged number of components serial: in-line combinedplanetary gearsets without using the two degrees of freedom to increase the number of gears a corresponding increase in the number of components is unavoidable ^abcdefghInnovationElasticity 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. whoseeconomicelasticity is greater than 1, are considered for realization Therequired innovationelasticity of an automobile manufacturer depends on its expected return on investment. The basic assumption that the relative additional benefit must beat 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) ^abDirect Predecessor To reflect the progress of the specific model change ^abcdefplus 1 reverse gear ^abcdof which 2 gearsets are combined as a compoundRavigneaux 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 fromGM Cruise-O-Matic fromFord TorqueFlite fromChrysler Detroit Gear fromBorgWarner forStudebaker BW-35 fromBorgWarner and asT35 fromAisin 3N 71 fromNissan/Jatco 3 HP fromZF Friedrichshafen W3A 040 and W3B 050 fromMercedes-Benz

The ratios of the 6 gears are nicely 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.

It has atorque converter lock-up for all 6 forward gears, which can be fully disengage when stationary, largely closing thefuel efficiency gap between vehicles with automatic andmanual transmissions.

In aLepelletier gearset,^[3] a conventionalplanetary gearset and a compositeRavigneaux gearset are combined to reduce both the size and weight as well as the manufacturing costs. Like all transmissions realized with Lepelletier transmissions, the6HP 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^[a][b]

In-Depth Analysis[c] With Assessment And Torque Ratio[d] And Efficiency Calculation[e]		Planetary Gearset: Teeth[f] Lepelletier gear mechanism			Count	Nomi- nal[g] Effec- tive[h]	Cen- ter[i]
		Simple	Ravigneaux				Avg.[j]
Make[k] Model	Version First Delivery	S1[l] R1[m]	S2[n] R2[o]	S3[p] R3[q]	Brakes Clutches	Ratio Span	Gear Step[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	${\displaystyle i_R}$[c]	${\displaystyle i_1}$[c]	${\displaystyle i_2}$[c]	${\displaystyle i_3}$[c]	${\displaystyle i_4}$[c]	${\displaystyle i_5}$[c]	${\displaystyle i_6}$[c]
Step[r]	${\displaystyle -\frac{i_R}{i_1}}$[s]	${\displaystyle \frac{i_1}{i_1}}$	${\displaystyle \frac{i_1}{i_2}}$[t]	${\displaystyle \frac{i_2}{i_3}}$	${\displaystyle \frac{i_3}{i_4}}$	${\displaystyle \frac{i_4}{i_5}}$	${\displaystyle \frac{i_5}{i_6}}$
Δ Step[u][v]			${\displaystyle \frac{i_1}{i_2}:\frac{i_2}{i_3}}$	${\displaystyle \frac{i_2}{i_3}:\frac{i_3}{i_4}}$	${\displaystyle \frac{i_3}{i_4}:\frac{i_4}{i_5}}$	${\displaystyle \frac{i_4}{i_5}:\frac{i_5}{i_6}}$
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[w]	${\displaystyle 0-\frac{i_1}{i_R}}$	${\displaystyle \frac{i_1}{i_1}-0}$	${\displaystyle \frac{i_1}{i_2}-\frac{i_1}{i_1}}$	${\displaystyle \frac{i_1}{i_3}-\frac{i_1}{i_2}}$	${\displaystyle \frac{i_1}{i_4}-\frac{i_1}{i_3}}$	${\displaystyle \frac{i_1}{i_5}-\frac{i_1}{i_4}}$	${\displaystyle \frac{i_1}{i_6}-\frac{i_1}{i_5}}$
Torque Ratio[d]	${\displaystyle {\mu }_R}$[d]	${\displaystyle {\mu }_1}$[d]	${\displaystyle {\mu }_2}$[d]	${\displaystyle {\mu }_3}$[d]	${\displaystyle {\mu }_4}$[d]	${\displaystyle {\mu }_5}$[d]	${\displaystyle {\mu }_6}$[d]
Efficiency ${\displaystyle {\eta }_n}$[e]	${\displaystyle \frac{{\mu }_R}{i_R}}$[e]	${\displaystyle \frac{{\mu }_1}{i_1}}$[e]	${\displaystyle \frac{{\mu }_2}{i_2}}$[e]	${\displaystyle \frac{{\mu }_3}{i_3}}$[e]	${\displaystyle \frac{{\mu }_4}{i_4}}$[e]	${\displaystyle \frac{{\mu }_5}{i_5}}$[e]	${\displaystyle \frac{{\mu }_6}{i_6}}$[e]
2000: 1st Generation
ZF 6HP 26[x] ZF 6HP 19[x] ZF 6HP 32[x]	600 N⋅m (443 lb⋅ft) 400 N⋅m (295 lb⋅ft)[y] 750 N⋅m (553 lb⋅ft)[6] 2000 (all)	37 71	31 38	38 85	2 3	6.0354 4.9236 [h][s]	1.6977
							1.4327[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	−3.4025[s][h] ${\displaystyle -\frac{4,590}{1,349}}$	4.1708 ${\displaystyle \frac{9,180}{2,201}}$	2.3397[t] ${\displaystyle \frac{211,140}{90,241}}$	1.5211 ${\displaystyle \frac{108}{71}}$	1.1428 [v][w] ${\displaystyle \frac{9,180}{8,033}}$	0.8672 ${\displaystyle \frac{4,590}{5,293}}$	0.6911 ${\displaystyle \frac{85}{123}}$
Step	0.8158[s]	1.0000	1.7826[t]	1.5382	1.3311	1.3178	1.2549
Δ Step[u]			1.1589	1.1559	1.0101[v]	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[w]	1.1599	1.2258
Torque Ratio[d]	–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 ${\displaystyle {\eta }_n}$[e]	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
2007: 2nd Generation
ZF 6HP 28[x] ZF 6HP 21[x] ZF 6HP 34[x]	600 N⋅m (443 lb⋅ft) 450 N⋅m (332 lb⋅ft)[z] 750 N⋅m (553 lb⋅ft)[aa] 2007 (all)	37 71	31 38	38 85	2 3	6.0354 4.9236 [h][s]	1.6977
							1.4327[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	−3.4025[s][h]	4.1708	2.3397[t]	1.5211	1.1428 [v][w]	0.8672	0.6911
Other Manufacturer using theLepelletier gear mechanism
Aisin AWTF-80 SC	450 N⋅m (332 lb⋅ft)[7] 2005	50 90	36 44	44 96	2 3	6.0494 4.9495 [h][s]	1.6865
							1.4333[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	−3.3939[s][h] ${\displaystyle -\frac{112}{33}}$	4.1481 ${\displaystyle \frac{112}{27}}$	2.3704[t] ${\displaystyle \frac{64}{27}}$	1.5556 ${\displaystyle \frac{14}{9}}$	1.1546[v] ${\displaystyle \frac{112}{97}}$	0.8593 ${\displaystyle \frac{336}{391}}$	0.6857[w] ${\displaystyle \frac{24}{35}}$
Step	0.8182[s]	1.0000	1.7500[t]	1.5238	1.3472	1.3436	1.2532
Δ Step[u]			1.1484	1.1311	1.0027[v]	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[w]
Torque Ratio[d]	–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 ${\displaystyle {\eta }_n}$[e]	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
Ford 6R 60 6R 80	600 N⋅m (443 lb⋅ft) 800 N⋅m (590 lb⋅ft) 2005 (all)	37 71	31 38	38 85	2 3	6.0354 4.9236 [h][s]	1.6977
							1.4327[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	−3.4025[s][h]	4.1708	2.3397[t]	1.5211	1.1428 [v][w]	0.8672	0.6911
Ford 6R 140	1,400 N⋅m (1,033 lb⋅ft) 2005	49 95	37 47	47 97	2 3	5.8993 4.6441 [h][s]	1.6361
							1.4261[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	−3.1283[s][h] ${\displaystyle -\frac{13,968}{4,485}}$	3.9738 ${\displaystyle \frac{13,968}{3,515}}$	2.3181 [t][v] ${\displaystyle \frac{8,148}{3,515}}$	1.5158 ${\displaystyle \frac{144}{95}}$	1.1492 [v][w] ${\displaystyle \frac{13,968}{12,155}}$	0.8585 ${\displaystyle \frac{13,968}{16,271}}$	0.6736 ${\displaystyle \frac{97}{144}}$
Step	0.7872[s]	1.0000	1.7143[t]	1.5293	1.3190	1.3389	1.2744
Δ Step[u]			1.1210[v]	1.1594	0.9854[v]	1.0504
Speed	-1.2703	1.0000	1.7143	2.6216	3.4580	4.6290	5.8993
Δ Speed	1.2703	1.0000	0.7143	0.9073	0.8364[w]	1.1710	1.2703
Torque Ratio[d]	–3.0449 –3.0035	3.8290 3.7576	2.2615 2.2333	1.5055 1.5003	1.1419 1.1383	0.8543 0.8522	0.6692 0.6669
Efficiency ${\displaystyle {\eta }_n}$[e]	0.9733 0.9601	0.9635 0.9456	0.9756 0.9635	0.9932 0.9898	0.9937 0.9906	0.9952 0.9927	0.9934 0.9900
GM 6L 45 6L 50	500 N⋅m (369 lb⋅ft) 2006	49 89	37 47	47 97	2 3	6.0346 4.7507 [h][s]	1.6548
							1.4326[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	−3.2001[s][h] ${\displaystyle -\frac{13,386}{4,183}}$	4.0650 ${\displaystyle \frac{13,386}{3,293}}$	2.3712 [t][v] ${\displaystyle \frac{15,617}{63586}}$	1.5506 ${\displaystyle \frac{138}{89}}$	1.1567 [v][w] ${\displaystyle \frac{13,386}{11,573}}$	0.8532 ${\displaystyle \frac{13,386}{15,689}}$	0.6736 ${\displaystyle \frac{97}{144}}$
Step	0.7872[s]	1.0000	1.7143[t]	1.5293	1.3406	1.3557	1.2662
Δ Step[u]			1.1210[v]	1.1408	0.9889[v]	1.0703
Speed	-1.2703	1.0000	1.7143	2.6216	3.5144	4.7643	6.0346
Δ Speed	1.2703	1.0000	0.7143	0.9073	0.8928[w]	1.2499	1.2703
Torque Ratio[d]	–3.1138 –3.0710	3.9156 3.8421	2.3127 2.2826	1.5396 1.5340	1.1490 1.1453	0.8490 0.8468	0.6692 0.6692
Efficiency ${\displaystyle {\eta }_n}$[e]	0.9730 0.9597	0.9633 0.9452	0.9753 0.9630	0.9929 0.9893	0.9934 0.9902	0.9951 0.9925	0.9934 0.9900
GM 6L 80 6L 90	800 N⋅m (590 lb⋅ft) 2005	50 94	35 46	46 92	2 3	6.0401 4.5957 [h][s]	1.6384
							1.4329[r]
Gear	R	1	2	3	4	5	6
Gear Ratio[c]	−3.0638[s][h] ${\displaystyle -\frac{144}{47}}$	4.0267 ${\displaystyle \frac{6,624}{1,645}}$	2.3635 [t][v] ${\displaystyle \frac{3,888}{1,645}}$	1.5319 ${\displaystyle \frac{72}{47}}$	1.1522 [v][w] ${\displaystyle \frac{6,624}{5,749}}$	0.8521 ${\displaystyle \frac{144}{169}}$	0.6667 ${\displaystyle \frac{2}{3}}$
Step	0.7609[s]	1.0000	1.7037[t]	1.5429	1.3296	1.3522	1.2781
Δ Step[u]			1.1043[v]	1.1604	0.9832[v]	1.0580
Speed	-1.3143	1.0000	1.7037	2.6286	3.4948	4.7258	6.0401
Δ Speed	1.3143	1.0000	0.7037	0.9249	0.8662[w]	1.2310	1.3143
Torque Ratio[d]	–2.9817 –2.9410	3.8794 3.8068	2.3048 2.2756	1.5213 1.5160	1.1448 1.1412	0.8478 0.8456	0.6622 0.6599
Efficiency ${\displaystyle {\eta }_n}$[e]	0.9732 0.9599	0.9634 0.9454	0.9751 0.9628	0.9931 0.9896	0.9936 0.9904	0.9950 0.9924	0.9932 0.9898
Actuated Shift Elements[ab]
Brake A[ac]		❶	❶	❶	❶
Brake B[ad]	❶			❶		❶
Clutch C[ae]			❶				❶
Clutch D[af]	❶	❶
Clutch E[ag]					❶	❶	❶
Geometric Ratios: Speed Conversion
Gear Ratio[c] R & 3 & 6 Ordinary[ah] Elementary Noted[ai]	${\displaystyle i_R=-\frac{R_3(S_1+R_1)}{R_1{S}_3}}$		${\displaystyle i_3=\frac{S_1+R_1}{R_1}}$		${\displaystyle i_6=\frac{R_3}{S_3+R_3}}$
	${\displaystyle i_R=-\left(1+\frac{S_1}{R_1}\right)\frac{R_3}{S_3}}$		${\displaystyle i_3=1+\frac{S_1}{R_1}}$		${\displaystyle i_6=\frac{1}{1+\frac{S_3}{R_3}}}$
Gear Ratio[c] 1 & 2 Ordinary[ah] Elementary Noted[ai]	${\displaystyle i_1=\frac{R_2{R}_3(S_1+R_1)}{R_1{S}_2{S}_3}}$			${\displaystyle i_2=\frac{R_3(S_1+R_1)(S_2+R_2)}{R_1{S}_2(S_3+R_3)}}$
	${\displaystyle i_1=\left(1+\frac{S_1}{R_1}\right)\frac{R_2{R}_3}{S_2{S}_3}}$			${\displaystyle i_2=\frac{\left(1+\frac{S_1}{R_1}\right)\left(1+\frac{R_2}{S_2}\right)}{1+\frac{S_3}{R_3}}}$
Gear Ratio[c] 4 & 5 Ordinary[ah] Elementary Noted[ai]	${\displaystyle i_4=\frac{R_2{R}_3(S_1+R_1)}{R_2{R}_3(S_1+R_1)-S_1{S}_2{S}_3}}$			${\displaystyle i_5=\frac{R_3(S_1+R_1)}{R_3(S_1+R_1)+S_1{S}_3}}$
	${\displaystyle i_4=\frac{1}{1-\frac{\frac{S_2{S}_3}{R_2{R}_3}}{1+\frac{R_1}{S_1}}}}$			${\displaystyle i_5=\frac{1}{1+\frac{\frac{S_3}{R_3}}{1+\frac{R_1}{S_1}}}}$
Kinetic Ratios: Torque Conversion
Torque Ratio[d] R & 3 & 6	${\displaystyle {\mu }_R=-\left(1+\frac{S_1}{R_1}{\eta }_0\right)\frac{R_3}{S_3}{\eta }_0}$		${\displaystyle {\mu }_3=1+\frac{S_1}{R_1}{\eta }_0}$		${\displaystyle {\mu }_6=\frac{1}{1+\frac{S_3}{R_3}\cdot \frac{1}{{\eta }_0}}}$
Torque Ratio[d] 1 & 2	${\displaystyle {\mu }_1=\left(1+\frac{S_1}{R_1}{\eta }_0\right)\frac{R_2{R}_3}{S_2{S}_3}{{\eta }_0}^{\frac{3}{2}}}$			${\displaystyle {\mu }_2=\frac{\left(1+\frac{S_1}{R_1}{\eta }_0\right)\left(1+\frac{R_2}{S_2}{\eta }_0\right)}{1+\frac{S_3}{R_3}\cdot \frac{1}{{\eta }_0}}}$
Torque Ratio[d] 4 & 5	${\displaystyle {\mu }_4=\frac{1}{1-\frac{\frac{S_2{S}_3}{R_2{R}_3}{{\eta }_0}^{\frac{3}{2}}}{1+\frac{R_1}{S_1}\cdot \frac{1}{{\eta }_0}}}}$			${\displaystyle {\mu }_5=\frac{1}{1+\frac{\frac{S_3}{R_3}\cdot \frac{1}{{\eta }_0}}{1+\frac{R_1}{S_1}{\eta }_0}}}$
^The 6HP-transmission is the first one to use theLepelletier gear mechanism ^Revised 14 January 2026 Nomenclature ${\displaystyle S_n=}$ sun gear: number of teeth ${\displaystyle R_n=}$ ring gear: number of teeth ${\displaystyle C_n=}$carrier or planetary gear carrier (not needed) ${\displaystyle s_n=}$ sun gear: shaft speed ${\displaystyle r_n=}$ ring gear: shaft speed ${\displaystyle c_n=}$ carrier or planetary gear carrier: shaft speed With${\displaystyle n=}$ gear is ${\displaystyle i_n=}$ gear ratio or transmission ratio ${\displaystyle {\omega }_{1;n}={\omega }_t=}$ shaft speed shaft 1: input (turbine) shaft ${\displaystyle {\omega }_{2;n}=}$ shaft speed shaft 2: output shaft ${\displaystyle T_{1;n}=T_t=}$ torque shaft 1: input (turbine) shaft ${\displaystyle T_{2;n}=}$ torque shaft 2: output shaft ${\displaystyle {\mu }_n=}$ torque ratio or torque conversion ratio ${\displaystyle {\eta }_n=}$ efficiency ${\displaystyle i_0=}$ stationary gear ratio ${\displaystyle {\eta }_0=}$ (assumed) stationary gear efficiency ^abcdefghijklmnopqrsGear Ratio (Transmission Ratio)${\displaystyle i_n}$ — Speed Conversion — Thegear ratio${\displaystyle i_n}$ is the ratio of input shaft speed${\displaystyle {\omega }_{1;n}}$ to output shaft speed${\displaystyle {\omega }_{2;n}}$ and therefore corresponds tothe reciprocal of the shaft speeds ${\displaystyle i_n=\frac{1}{\frac{{\omega }_{2;n}}{{\omega }_{1;n}}}=\frac{{\omega }_{1;n}}{{\omega }_{2;n}}=\frac{{\omega }_t}{{\omega }_{2;n}}}$ ^abcdefghijklmnopqTorque Ratio (Torque Conversion Ratio)${\displaystyle {\mu }_n}$ — Torque Conversion — Thetorque ratio${\displaystyle {\mu }_n}$ is the ratio of output torque${\displaystyle T_{2;n}}$ to input torque${\displaystyle T_{1;n}}$ minus efficiency losses and therefore corresponds (apart from the efficiency losses) tothe reciprocal of the shaft speeds too ${\displaystyle {\mu }_n=i_n{\eta }_{n;{\eta }_0}=\frac{{\omega }_{1;n}{\eta }_{n;{\eta }_0}}{{\omega }_{2;n}}=\frac{T_{2;n}{\eta }_{n;{\eta }_0}}{T_{1;n}}}$ whereby${\displaystyle {\eta }_{n;{\eta }_0}}$ may vary from gear to gear according to the formulas listed in this table and${\displaystyle 0\le {\eta }_{n;{\eta }_0}\le 1}$ ^abcdefghijklmnEfficiency Theefficiency${\displaystyle {\eta }_n}$ is calculated from the torque ratio in relation to the gear ratio (transmission ratio) ${\displaystyle {\eta }_n=\frac{{\mu }_n}{i_n}}$ 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 Corridor for torque ratio and efficiency in planetary gearsets, thestationary 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 thestationary 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${\displaystyle {{\eta }_0}^{\frac{1}{2}}}$ at${\displaystyle {0.9800}^{\frac{1}{2}}=0.98995}$ (upper value) and${\displaystyle {0.9700}^{\frac{1}{2}}=0.98489}$ (lower value) ^Layout Input and output are on opposite sides Planetary gearset 1 is on the input (turbine) side Input (turbine) shafts areR1 and, if actuated,C2/C3 (the common carrier of the compound Ravigneaux gearset) Output shaft isR3 (ring gear of outer Ravigneaux gearset) ^Total Ratio Span (Total Gear/Transmission Ratio) Nominal ${\displaystyle \frac{{\omega }_{2;n}}{{\omega }_{2;1}}=\frac{\frac{{\omega }_{2;n}}{{\omega }_{2;1}{\omega }_{2;n}}}{\frac{{\omega }_{2;1}}{{\omega }_{2;1}{\omega }_{2;n}}}=\frac{\frac{1}{{\omega }_{2;1}}}{\frac{1}{{\omega }_{2;n}}}=\frac{\frac{{\omega }_t}{{\omega }_{2;1}}}{\frac{{\omega }_t}{{\omega }_{2;n}}}=\frac{i_1}{i_n}}$ 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 ^abcdefghijklmnoTotal Ratio Span (Total Gear Ratio/Total Transmission Ratio) Effective ${\displaystyle \frac{{\omega }_{2;n}}{max({\omega }_{2;1};|{\omega }_{2;R}|)}=\frac{min(i_1;|i_R|)}{i_n}}$ The span is only effective to the extent that the reverse gear ratio matches that of 1st gear see alsoStandard R:1 Digression Reverse gear is usuallylonger than 1st gear theeffective span is therefore ofcentral importance for describing the suitability of a transmission because in these cases, thenominal spread conveys a misleading picture which is only unproblematic for vehicles with high specific power Market participants Manufacturers naturally have no interest in specifying the effective span Users have not yet formulated the practical benefits that the effective span has for them The effective span has not yet played a role in research and teaching Contrary to its significance theeffective span has thereforenot yet been able to establish itself eitherin theory orin practice. End of digression ^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 ${\displaystyle {\left(\frac{{\omega }_{2;n}}{{\omega }_{2;1}}\right)}^{\frac{1}{n-1}}={\left(\frac{i_1}{i_n}\right)}^{\frac{1}{n-1}}}$ There are${\displaystyle n-1}$ gear steps between${\displaystyle n}$ gears with decreasing step width the gears connect better to each other shifting comfort increases ^Manufacturer ^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 ^abcdefghiStandard 50:50 — 50 % Is Above And 50 % Is Below The Average Gear Step — With steadily decreasing gear steps (yellow highlighted lineStep) and a particularly large step from 1st to 2nd gear thelower half of the gear steps (between the small gears; rounded down, here the first 2)is always larger and theupper half of the gear steps (between the large gears; rounded up, here the last 3)is always smaller than the average gear step (cell highlightedyellow 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) ^abcdefghijklmnopqrstStandard 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 alsoTotal Ratio Span (Total Gear/Transmission Ratio) Effective ^abcdefghijklmStandard 1:2 — Gear Step 1st To 2nd Gear As Small As Possible — With continuously decreasing gear steps (yellow marked lineStep) thelargest 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) ^abcdefFrom large to small gears (from right to left) ^abcdefghijklmnopqrsStandard STEP — From Large To Small Gears: Steady And Progressive Increase In Gear Steps — Gear steps should increase: Δ Step (firstgreen highlighted lineΔ Step) is always greater than 1 Asprogressive as possible: Δ Step is always greater than the previous step Not progressively increasing is acceptable (red) Not increasing is unsatisfactory (bold) ^abcdefghijklmStandard SPEED — From Small To Large Gears: Steady Increase In Shaft Speed Difference — Shaft speed differences should increase: Δ Shaft Speed (second line marked ingreenΔ (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) ^abcdefforRear-wheel drive cars ^400 N⋅m (295 lbf⋅ft) or 400 N⋅m (295 lbf⋅ft) ^produced in the PRC,[5] alternatively known as 6HP 19tu and 6HP 19z ^planned, but never went into production[2] ^ Permanentlycoupled elements Apart from Ravigneaux couplings, there areno permanent couplings ^ BlocksR2 andS3 ^ BlocksC2/C3 (the common carrier of the compound Ravigneaux gearset) ^ CouplesC1 andS2 ^ CouplesC1 withR2 andS3 ^ CouplesR1 withC2/C3 (the common carrier of the compound Ravigneaux gearset) ^abcOrdinary Noted For direct determination of the ratio ^abcElementary 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 the torque conversion rate and efficiency