9HP is thetrademark name for theZF Friedrichshafen 9-speedautomatic transmission models (9-speed transmission withHydraulic converter andPlanetary gearsets) fortransverse engine applications, designed by ZF's subsidiary inSaarbrücken and built inGray Court, South Carolina.^[1] It is used infront-wheel drive andall-wheel drive vehicles.

The 9HP is the world's first 9-speed automatic transmission for passenger cars.Land Rover andJeep launched it at the 2013Geneva Motor Show.^[2] The2014 Jeep Cherokee then was the first car with this transmission delivered to customers.

Gearset Concept: Cost-Effectiveness^[a]

With Assessment	Output: Gear Ratios	Innovation Elasticity[b] Δ Output : Δ Input	Input: Main Components
			Total	Gearsets	Brakes	Clutches
9HP 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 ${\displaystyle \frac{n_{O1}-n_{O2}}{n_{O2}}}$	${\displaystyle \frac{n_{O1}-n_{O2}}{n_{O2}}:\frac{n_{I1}-n_{I2}}{n_{I2}}}$ ${\displaystyle =\frac{n_{O1}-n_{O2}}{n_{O2}}\cdot \frac{n_{I2}}{n_{I1}-n_{I2}}}$	Δ Input ${\displaystyle \frac{n_{I1}-n_{I2}}{n_{I2}}}$	${\displaystyle \frac{n_{G1}-n_{G2}}{n_{G2}}}$	${\displaystyle \frac{n_{B1}-n_{B2}}{n_{B2}}}$	${\displaystyle \frac{n_{C1}-n_{C2}}{n_{C2}}}$
9HP 4HP[c]	9[d] 4[d]	Progress[b]	10 7	4 2[e]	3 2	3 3
Δ Number	5		3	2	1	0
Relative Δ	1.250 ${\displaystyle \frac{5}{4}}$	2.917[b] ${\displaystyle \frac{5}{4}:\frac{3}{7}=\frac{5}{4}\cdot \frac{7}{3}=\frac{35}{12}}$	0.429 ${\displaystyle \frac{3}{7}}$	1.000 ${\displaystyle \frac{2}{2}}$	0.500 ${\displaystyle \frac{1}{2}}$	0.000 ${\displaystyle \frac{0}{3}}$
9HP Aisin[f]	9[d] 4[d]	Progress[b]	10 8	4 3[g]	3 2	3 3
Δ Number	3		2	1	1	0
Relative Δ	0.500 ${\displaystyle \frac{3}{6}}$	2.000[b] ${\displaystyle \frac{3}{6}:\frac{2}{8}=\frac{1}{2}\cdot \frac{4}{1}=\frac{2}{1}}$	0.250 ${\displaystyle \frac{2}{8}}$	0.333 ${\displaystyle \frac{1}{3}}$	0.333 ${\displaystyle \frac{-1}{3}}$	0.000 ${\displaystyle \frac{0}{3}}$
9HP 8HP[h]	9[d] 8[d]	Current Market Position[b]	10 9	4 4	3 2	3 3
Δ Number	1		1	0	1	0
Relative Δ	0.125 ${\displaystyle \frac{1}{8}}$	1.125[b] ${\displaystyle \frac{1}{8}:\frac{1}{9}=\frac{1}{8}\cdot \frac{9}{1}=\frac{9}{8}}$	0.111 ${\displaystyle \frac{1}{9}}$	0.000 ${\displaystyle \frac{0}{4}}$	0.500 ${\displaystyle \frac{1}{2}}$	0.000 ${\displaystyle \frac{0}{3}}$
W9A 3-Speed[i]	9[d] 3[d]	Historical Market Position[b]	10 7	4 2	3 3	3 2
Δ Number	6		3	2	0	1
Relative Δ	2.000 ${\displaystyle \frac{6}{3}}$	4.667[b] ${\displaystyle \frac{6}{3}:\frac{3}{7}=\frac{2}{1}\cdot \frac{7}{3}=\frac{14}{3}}$	0.429 ${\displaystyle \frac{3}{7}}$	1.000 ${\displaystyle \frac{1}{1}}$	0.000 ${\displaystyle \frac{0}{3}}$	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 ^abcdefghijInnovationElasticity 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) ^Direct Predecessor To reflect the progress of the specific model change ^abcdefghplus 1 reverse gear ^combined as a compoundRavigneaux gearset ^Market Predecessor As the reference standard fortransverse engine vehicles, theAisinsAWTF-80 SC reflects the progress for car manufacturer and customer at that time ^of which two gearstets are combined as a compoundRavigneaux gearset ^Current Reference Standard (Benchmark) The 8HP has become the new reference standard (benchmark) for automatic transmissions. Although designed for longitudinal installation, it is nevertheless the industry standard. ^Historical 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 9HP is only 0.24 inches (6 mm) longer than, and weighs 16.5 lbs (7.5 kg) less than, the outgoing six-speed transmission. The compact packaging is achieved by using a number of innovative design features: a new compact hydraulic vane-type pump, two patenteddog clutches,^[3] which replace bulkier conventional clutch packs, and a nested gear set.^[2] ZF claims that it is able to save an average of 16% in fuel compared with current 6-speed automatic transmissions.^[1]

Gear Ratio Analysis

In-Depth Analysis With Assessment[a]				Planetary Gearset: Teeth[b]				Count	Nomi- nal[c] Effec- tive[d]	Cen- ter[e]
										Avg.[f]
Model Type	Version First Delivery · Weight			S4[g] R4[h]	S3[i] R3[j]	S2[k] R2[l]	S1[m] R1[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 ${\displaystyle i_6}$	7 ${\displaystyle i_7}$	8 ${\displaystyle i_8}$	9 ${\displaystyle i_9}$
Step[o]	${\displaystyle -\frac{i_R}{i_1}}$[p]	${\displaystyle \frac{i_1}{i_1}}$	${\displaystyle \frac{i_1}{i_2}}$[q]	${\displaystyle \frac{i_2}{i_3}}$	${\displaystyle \frac{i_3}{i_4}}$	${\displaystyle \frac{i_4}{i_5}}$	${\displaystyle \frac{i_5}{i_6}}$	${\displaystyle \frac{i_6}{i_7}}$	${\displaystyle \frac{i_7}{i_8}}$	${\displaystyle \frac{i_8}{i_9}}$
Δ Step[r][s]			${\displaystyle \frac{i_1}{i_2}:\frac{i_2}{i_3}}$	${\displaystyle \frac{i_2}{i_3}:\frac{i_3}{i_4}}$	${\displaystyle \frac{i_3}{i_4}:\frac{i_4}{i_5}}$	${\displaystyle \frac{i_4}{i_5}:\frac{i_5}{i_6}}$	${\displaystyle \frac{i_5}{i_6}:\frac{i_6}{i_7}}$	${\displaystyle \frac{i_6}{i_7}:\frac{i_7}{i_8}}$	${\displaystyle \frac{i_7}{i_8}:\frac{i_8}{i_9}}$
Shaft Speed	${\displaystyle \frac{i_1}{i_R}}$	${\displaystyle \frac{i_1}{i_1}}$	${\displaystyle \frac{i_1}{i_2}}$	${\displaystyle \frac{i_1}{i_3}}$	${\displaystyle \frac{i_1}{i_4}}$	${\displaystyle \frac{i_1}{i_5}}$	${\displaystyle \frac{i_1}{i_6}}$	${\displaystyle \frac{i_1}{i_7}}$	${\displaystyle \frac{i_1}{i_8}}$	${\displaystyle \frac{i_1}{i_9}}$
Δ Shaft Speed[t]	${\displaystyle 0-\frac{i_1}{i_R}}$	${\displaystyle \frac{i_1}{i_1}-0}$	${\displaystyle \frac{i_1}{i_2}-\frac{i_1}{i_1}}$	${\displaystyle \frac{i_1}{i_3}-\frac{i_1}{i_2}}$	${\displaystyle \frac{i_1}{i_4}-\frac{i_1}{i_3}}$	${\displaystyle \frac{i_1}{i_5}-\frac{i_1}{i_4}}$	${\displaystyle \frac{i_1}{i_6}-\frac{i_1}{i_5}}$	${\displaystyle \frac{i_1}{i_7}-\frac{i_1}{i_6}}$	${\displaystyle \frac{i_1}{i_8}-\frac{i_1}{i_7}}$	${\displaystyle \frac{i_1}{i_9}-\frac{i_1}{i_8}}$
Specific Torque[u]	${\displaystyle \frac{T_{2;R}}{T_{1;R}}}$[v]	${\displaystyle \frac{T_{2;1}}{T_{1;1}}}$[v]	${\displaystyle \frac{T_{2;2}}{T_{1;2}}}$[v]	${\displaystyle \frac{T_{2;3}}{T_{1;3}}}$[v]	${\displaystyle \frac{T_{2;4}}{T_{1;4}}}$[v]	${\displaystyle \frac{T_{2;5}}{T_{1;5}}}$[v]	${\displaystyle \frac{T_{2;6}}{T_{1;6}}}$[v]	${\displaystyle \frac{T_{2;7}}{T_{1;7}}}$[v]	${\displaystyle \frac{T_{2;8}}{T_{1;8}}}$[v]	${\displaystyle \frac{T_{2;9}}{T_{1;9}}}$[v]
Efficiency ${\displaystyle {\eta }_n}$[u]	${\displaystyle \frac{T_{2;R}}{T_{1;R}}:i_R}$	${\displaystyle \frac{T_{2;1}}{T_{1;1}}:i_1}$	${\displaystyle \frac{T_{2;2}}{T_{1;2}}:i_2}$	${\displaystyle \frac{T_{2;3}}{T_{1;3}}:i_3}$	${\displaystyle \frac{T_{2;4}}{T_{1;4}}:i_4}$	${\displaystyle \frac{T_{2;5}}{T_{1;5}}:i_5}$	${\displaystyle \frac{T_{2;6}}{T_{1;6}}:i_6}$	${\displaystyle \frac{T_{2;7}}{T_{1;7}}:i_7}$	${\displaystyle \frac{T_{2;8}}{T_{1;8}}:i_8}$	${\displaystyle \frac{T_{2;9}}{T_{1;9}}:i_9}$
9HP 28 9HP 48	280 Nm[w] · 2013 · 78 kg (172 lb) 480 Nm[x] · 2013 · 86 kg (190 lb)			42 110	42 110	91 133	42 86	3[y] 3[z]	9.8085 7.9402	1.5007
										1.3303[o]
Gear Ratio	−3.8049[p] ${\displaystyle -\frac{3,142,144}{825,825}}$	4.7001 ${\displaystyle \frac{184,832}{39,325}}$	2.8419 ${\displaystyle \frac{369,664}{130,075}}$	1.9094 ${\displaystyle \frac{5,776}{3,025}}$	1.3818[s] ${\displaystyle \frac{76}{55}}$	1.0000 ${\displaystyle \frac{1}{1}}$	0.8081[t] ${\displaystyle \frac{34,048}{42,133}}$	0.6995[s][t] ${\displaystyle \frac{6,272}{8,967}}$	0.5802[s] ${\displaystyle \frac{76}{131}}$	0.4792 ${\displaystyle \frac{2,176}{4,541}}$
Step	0.8095[p]	1.0000	1.6538	1.4884	1.3818	1.3818	1.2375	1.1553	1.2056	1.2107
Δ Step[r]			1.1112	1.0771	1.0000[s]	1.1167	1.0711	0.9583[s]	0.9958[s]
Speed	-1.2353	1.0000	1.6538	2.4615	3.4014	4.7001	5.5816	6.7197	8.1015	9.8085
Δ Speed	1.2353	1.0000	0.6538	0.8077	0.9399	1.2987	1.1161[t]	0.9035[t]	1.3818	1.7066
Specific Torque[u]	-3.5391 –3.4099	4.5931 4.5402	2.7922 2.7675	1.8884 1.8779	1.3742 1.3704	1.0000	0.8005 0.7966	0.6904 0.6857	0.5717 0.5673	0.4653 0.4582
Efficiency ${\displaystyle {\eta }_n}$[u]	0.9302 0.8962	0.9772 0.9660	0.9825 0.9738	0.9890 0.9835	0.9945 0.9917	1.0000	0.9906 0.9857	0.9870 0.9803	0.9854 0.9779	0.9710 0.9561
Actuated Shift Elements[aa]
Brake A[ab]	❶	❶	❶	❶	❶
Brake C[ac]			❶				❶		❶
Brake D[ad]	❶	❶						❶	❶	❶
Clutch B[ae]	❶			❶		❶				❶
Clutch E[af]					❶	❶	❶	❶	❶	❶
Clutch F[ag]		❶	❶	❶	❶	❶	❶	❶
Geometric Ratios
Ratio R & 1 Ordinary[ah] Elementary Noted[ai]	${\displaystyle i_R=\frac{(S_1{S}_2-R_1{R}_2)(S_3+R_3)(S_4+R_4)}{S_1{S}_2{R}_3{R}_4}}$					${\displaystyle i_1=\frac{(S_2+R_2)(S_3+R_3)(S_4+R_4)}{S_2{R}_3{R}_4}}$
	${\displaystyle i_R=\left(1-\frac{R_1{R}_2}{S_1{S}_2}\right)\left(1+\frac{S_3}{R_3}\right)\left(1+\frac{S_4}{R_4}\right)}$					${\displaystyle i_1=\left(1+\frac{R_2}{S_2}\right)\left(1+\frac{S_3}{R_3}\right)\left(1+\frac{S_4}{R_4}\right)}$
Ratio 2 & 3 Ordinary[ah] Elementary Noted[ai]	${\displaystyle i_2=\frac{(S_1+R_1)(S_3+R_3)(S_4+R_4)}{R_1{R}_3{R}_4}}$					${\displaystyle i_3=\frac{(S_3+R_3)(S_4+R_4)}{R_3{R}_4}}$
	${\displaystyle i_2=\left(1+\frac{S_1}{R_1}\right)\left(1+\frac{S_3}{R_3}\right)\left(1+\frac{S_4}{R_4}\right)}$					${\displaystyle i_3=\left(1+\frac{S_3}{R_3}\right)\left(1+\frac{S_4}{R_4}\right)}$
Ratio 5–7 Ordinary[ah] Elementary Noted[ai]	${\displaystyle i_5=\frac{1}{1}}$	${\displaystyle i_6=\frac{S_3(S_1+R_1)(S_4+R_4)}{S_3(S_1+R_1)(S_4+R_4)+S_1{R}_3{S}_4}}$					${\displaystyle i_7=\frac{S_3(S_2+R_2)(S_4+R_4)}{S_3(S_2+R_2)(S_4+R_4)+R_2{R}_3{S}_4}}$
		${\displaystyle i_6=\frac{1}{1+\frac{\frac{R_3}{S_3}}{\left(1+\frac{R_1}{S_1}\right)\left(1+\frac{R_4}{S_4}\right)}}}$					${\displaystyle i_7=\frac{1}{1+\frac{\frac{R_3}{S_3}}{\left(1+\frac{S_2}{R_2}\right)\left(1+\frac{R_4}{S_4}\right)}}}$
Ratio 4 & 8 & 9 Ordinary[ah] Elementary Noted[ai]	${\displaystyle i_4=\frac{S_4+R_4}{R_4}}$		${\displaystyle i_8=\frac{S_3(S_4+R_4)}{S_4(S_3+R_3)+S_3{R}_4}}$			${\displaystyle i_9=\frac{S_3(R_1{R}_2-S_1{S}_2)(S4+R_4)}{S_3(R_1{R}_2-S_1{S}_2)(S_4+R_4)+R_1{R}_2{R}_3{S}_4}}$
	${\displaystyle i_4=1+\frac{S_4}{R_4}}$		${\displaystyle i_8=\frac{1}{1+\frac{\frac{R_3}{S_3}}{1+\frac{R_4}{S_4}}}}$			${\displaystyle i_9=\frac{1}{1+\frac{\frac{R_3}{S_3}}{\left(1-\frac{S_1{S}_2}{R_1{R}_2}\right)\left(1+\frac{R_4}{S_4}\right)}}}$
Kinetic Ratios
Specific Torque[u] R & 1	${\displaystyle \frac{T_{2;R}}{T_{1;R}}=\left(1-\frac{R_1{R}_2}{S_1{S}_2}{{\eta }_0}^2\right)\left(1+\frac{S_3}{R_3}{\eta }_0\right)\left(1+\frac{S_4}{R_4}{\eta }_0\right)}$					${\displaystyle \frac{T_{2;1}}{T_{1;1}}=\left(1+\frac{R_2}{S_2}{\eta }_0\right)\left(1+\frac{S_3}{R_3}{\eta }_0\right)\left(1+\frac{S_4}{R_4}{\eta }_0\right)}$
Specific Torque[u] 2 & 3	${\displaystyle \frac{T_{2;2}}{T_{1;2}}=\left(1+\frac{S_1}{R_1}{\eta }_0\right)\left(1+\frac{S_3}{R_3}{\eta }_0\right)\left(1+\frac{S_4}{R_4}{\eta }_0\right)}$					${\displaystyle \frac{T_{2;3}}{T_{1;3}}=\left(1+\frac{S_3}{R_3}{\eta }_0\right)\left(1+\frac{S_4}{R_4}{\eta }_0\right)}$
Specific Torque[u] 5–7	${\displaystyle \frac{T_{2;5}}{T_{1;5}}=\frac{1}{1}}$	${\displaystyle \frac{T_{2;6}}{T_{1;6}}=\frac{1}{1+\frac{\frac{R_3}{S_3}\cdot \frac{1}{{\eta }_0}}{\left(1+\frac{R_1}{S_1}{\eta }_0\right)\left(1+\frac{R_4}{S_4}{\eta }_0\right)}}}$					${\displaystyle \frac{T_{2;7}}{T_{1;7}}=\frac{1}{1+\frac{\frac{R_3}{S_3}\cdot \frac{1}{{\eta }_0}}{\left(1+\frac{S_2}{R_2}{\eta }_0\right)\left(1+\frac{R_4}{S_4}{\eta }_0\right)}}}$
Specific Torque[u] 4 & 8 & 9	${\displaystyle \frac{T_{2;4}}{T_{1;4}}=1+\frac{S_4}{R_4}{\eta }_0}$		${\displaystyle \frac{T_{2;8}}{T_{1;8}}=\frac{1}{1+\frac{\frac{R_3}{S_3}\cdot \frac{1}{{\eta }_0}}{1+\frac{R_4}{S_4}{\eta }_0}}}$			${\displaystyle \frac{T_{2;9}}{T_{1;9}}=\frac{1}{1+\frac{\frac{R_3}{S_3}\cdot \frac{1}{{\eta }_0}}{\left(1-\frac{S_1{S}_2}{R_1{R}_2}\cdot \frac{1}{{{\eta }_0}^2}\right)\left(1+\frac{R_4}{S_4}{\eta }_0\right)}}}$
^Revised 15 November 2025 ^Layout Input and output are on the same side Planetary gearset 4 is on the input (turbine) side Input shafts are, if actuated,S1,R1 + S3, andC3 (planetary gear carrier of gearset 1) + R4 Output shaft isC4 (planetary gear carrier of gearset 4) ^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 ^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 corresponds to that of 1st gear see alsoStandard 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 ${\displaystyle (\frac{i_1}{i_n}{)}^{\frac{1}{n-1}}}$ With decreasing step width the gears connect better to each other shifting comfort increases ^Sun 4: sun gear of gearset 4 ^Ring 4: ring gear of gearset 4 ^Sun 3: sun gear of gearset 3 ^Ring 3: ring gear of gearset 3 ^Sun 2: sun gear of gearset 2 ^Ring 2: ring gear of gearset 2 ^Sun 1: sun gear of gearset 1 ^Ring 1: ring gear of gearset 1 ^abcStandard 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 4)is always larger and theupper half of the gear steps (between the large gears; rounded up, here the last 4)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) ^abcStandard 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) ^Standard 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) ^abFrom large to small gears (from right to left) ^abcdefgStandard 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) ^abcdeStandard 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) ^abcdefghSpecific 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${\displaystyle n=gear}$ Theefficiency 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 ^abcdefghijCorridor 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${\displaystyle {{\eta }_0}^{\frac{1}{2}}}$ at${\displaystyle {0.9800}^{\frac{1}{2}}=0.98995}$ (upper value) and${\displaystyle {0.9700}^{\frac{1}{2}}=0.98489}$ (lower value) ^280 N⋅m (207 lb⋅ft) for both gasoline and diesel[1] ^450 N⋅m (332 lb⋅ft) for gasoline 480 N⋅m (354 lb⋅ft) for diesel[1] ^Thereof 1 dog break[3] ^Thereof 1 dog clutch[3] ^Permanentlycoupled elements C1, C2, andR3 S3 andS4 C3 and R4 ^Dog brake blocksS3 andS4 ^BlocksS1 ^BlocksR2 ^CouplesS1 with input shaft ^CouplesC3 (carrier 3) andR4 with input shaft ^Dog clutch couplesR1 andS2 with input shaft ^abcdOrdinary Noted For direct determination of the ratio ^abcdElementary Noted Alternative representation for determining the transmission ratio Contains only operands With ordinary 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 efficiency1

An Animated Drive Line Schematic & A Rotational Speeds Nomogram

These ordinates are positioned on the abscissa in strict accordance with the proportions of the sun gears' teeth numbers relative to those of their rings. Consequently, the output ratios on the ordinateC₄ (carrier of planetary gearset 4) follows closely to those of the actual transmission. Note that elements A and F are labelled swapped (cf. legend below).

▶️ Interactive NomogramArchived 2017-02-02 at theWayback Machine

This interactivenomogram is a real geometric calculator exactly representing the rotational speeds of the transmission's3x4 = 12 internal shafts for each of its9 ratios (+reverse), grouped according to their5 permanent coupling on4 joint ordinates and3 independent ordinates. These ordinates are positioned on theabscissa in strict accordance with the proportions of the sun gears' teeth numbers relative to those of their rings. Consequently, theoutput ratios on the6th ordinate (carrier of the fourth planetary gearset) follows closely those of the actual transmission. This advantageous geometric construction sets us free fromRobert Willis' famous and tedious formula,^[4] because all calculations are exclusively determined by lengths ratios, respectively teeth numbers on theabscissa for the 4 epicyclic ratios, and of rotational speeds on the6th ordinate for the 10 gear ratios.

A: Dog brake (blocksS₃ andS₄)
C: Brake (blocksS₁)
D: Brake (blocksR₂)
B: Clutch (couplesS₁ with input shaft)
E: Clutch (couplesC₃ (carrier 3) andR₄ with input shaft)
F: Dog clutch (couplesR₁ andS₂ with input shaft)

The transmission has been problematic, as customers of Jeep, Chrysler, and Acura models equipped with the transmission have experienced problems in their vehicles regarding slow shifting and noisy operation. ZF has said this is due to software problems, not mechanical issues.^[8]

Chrysler issued Technical Service Bulletins (TSB) for the 2014Jeep Cherokee to "fix rough and delayed gearshifts", and Acura has issued transmission-related recalls for the 2015Acura TLX.^[9][10]

Production of the 9HP started in 2013 at ZF's Gray Court facility inLaurens, South Carolina. 400,000 units are produced per year.^[11]

Production of the 9HP for Fiat and Chrysler vehicles began in May 2013 at Indiana Transmission Plant I (ITPI), followed by Tipton Transmission Plant in Tipton County, Indiana in May 2014.^[12]

• ZF Friedrichshafen transmissions

• All articles with dead external links
• Articles with dead external links from August 2025
• Articles with permanently dead external links
• Articles with short description
• Short description is different from Wikidata
• Short description matches Wikidata
• Webarchive template wayback links