Engineering:GM 8L transmission

8L 45 · 8L 90 · 8L 80
8L 45 · 8L 90 · 8L 80
Overview
Manufacturer	General Motors
Production	2014–present
Body and chassis
Class	8-speed longitudinal automatic transmission
Related	ZF 8HP · Aisin-Toyota 8-speed · MB 9G-Tronic
Chronology
Predecessor	6L 45 · 6L 50 · 6L 80 · 6L 90
Successor	10L 80 · 10L 90 · 10L 1000

Short description: Motor vehicle automatic transmission models

All 8L transmissions are based on the same globally patented gearset concept as the ZF 8HP from 2008. While fully retaining the same gearset logic, they differ only in the patented^[1] arrangement of the components, with gearsets 1 and 3 swapped.^[2]

The 8L 90 is the first 8-speed automatic transmission built by General Motors. It debuted in 2014 and is designed for use in longitudinal engine applications, either attached to the front-located engine^[3] with a standard bell housing or mounted in the rear of the car adjacent to the differential (as in the Corvette). It features a hydraulic (Hydramatic) design.

The 8L 45 is the smaller variant and debuted in 2015 in the 2016 Cadillac CT6. It is designed for use in longitudinal engine applications attached to the front-located engine^[3] with a standard bell housing. It is a hydraulic (Hydramatic) design sharing much with the 8L 90 transmission.^[4] Estimated weight savings over the heavier-duty 8L 90 is 33 lb (15 kg). A second generation of the 8L 45 was introduced in 2023 model years with a new RPO^[5] code N8R^[6]

The 8L 80 is an updated version with a new RPO^[5] code MFC. Debuted in the 2023 model years of the Chevrolet Colorado and GMC Canyon.^[7]

Key Data

Gear Ratios^{[lower-alpha 1]}^[8]
Model	Type	First Delivery	Gear									Total Span			Avg. Step	Components		Nomenclature
Model	Type	First Delivery	R	1	2	3	4	5	6	7	8	Nomi- nal	Effec- tive	Cen- ter	Avg. Step	Total	per Gear^{[lower-alpha 2]}	Gears Count	Cou- pling	Gear- sets	Maximum Input Torque

8L 90 · 8L 80	M5U · MFC+N8X	2014 · 2023	−3.818	4.560	2.971	2.075	1.688	1.270	1.000	0.845	0.652	6.999	5.860	1.724	1.320	4 Gearsets 2 Brakes 3 Clutches	1.125	6^{[lower-alpha 2]}	Installation L^{[lower-alpha 3]}		900 N⋅m (664 lb⋅ft)^[9]
8L 45	M5N · N8R	2015 · 2023	−3.928	4.615	3.038	2.065	1.658	1.259	1.000	0.849	0.658	7.011	5.966	1.743	1.321				Installation L^{[lower-alpha 3]}		500 N⋅m (369 lb⋅ft)

ZF 8HP 70^{[lower-alpha 4]}		2008	−3.297	4.696	3.130	2.104	1.667	1.285	1.000	0.839	0.667	7.043	4.945	1.769	1.322				H^{[lower-alpha 5]}	P^{[lower-alpha 6]}	400 N⋅m (295 lb⋅ft) – 750 N⋅m (553 lb⋅ft)

↑ Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage ↑ ^2.0 ^2.1 Forward gears only ↑ Longitudinal engine ↑ first transmission to use this 8-speed gearset concept. It has become the new benchmark for automatic transmissions ↑ Hydraulic torque converter · German: Hydraulischer Wandler oder Drehmomentwandler ↑ Planetary gearing · German: Planetenradsätze

Specifications

Features
	8L 45 M5N + N8R^[10]	8L 90 M5U 8L 80 MFC + N8X^[11]

Input Capacity
Maximum engine power	308 bhp (230 kW)^{[lower-alpha 1]}	420 bhp (313 kW)^{[lower-alpha 2]}
Maximum gearbox torque	550 N⋅m (406 lb⋅ft)^{[lower-alpha 1]}	900 N⋅m (664 lb⋅ft)^{[lower-alpha 2]}
Maximum shift speed	7,500/min	6,000/min
Vehicle
Maximum Validated Weight Gross Vehicle Weight · GVW	—	—
Maximum Validated Weight Gross Curb Vehicle Weight · GCVW	12,000 lb (5,440 kg)^{[lower-alpha 1]}	22,500 lb (10,210 kg)^{[lower-alpha 2]}
Sundry
Range-selector quadrant	P · R · N · D · M · L
Case description	2-piece main, bell integrated with main
Case material	Die cast aluminum
Shift pattern (2)	2 on/off solenoids
Shift quality	6 Variable Force Solenoids · 1 for each clutch · 1 for TCC
Torque converter clutch	Variable Force Solenoid ECCC · 2 path · turbine damper
Converter size	238 mm (9.37 in)	258 mm (10.16 in)
Fluid type	DEXRON High Performance ATF
Fluid capacity	10.8 l (11.4 US qt)^{[lower-alpha 1]}	10.3 l (10.9 US qt)^{[lower-alpha 2]}
Weight	80 kg (176 lb)^{[lower-alpha 1]}	98.9 kg (218 lb)^{[lower-alpha 2]}
Available Control Features
Shift Patterns	Multiple (Selectable)
Driver Shift Control	Tap Up and Down
Additional Modes	Tow & Haul Mode (Selectable)
Engine Torque Management	On All Shifts
Shift Control	Automatic Start/Stop Automatic Grade Braking
Assembly sites	GMPT^{[lower-alpha 3]} Toledo · Ohio · USA GMPT^{[lower-alpha 3]} Silao · Mexico

↑ ^1.0 ^1.1 ^1.2 ^1.3 ^1.4 based on 2020 Chevrolet Colorado Z71 2WD Crew Cab · Short Bed ↑ ^2.0 ^2.1 ^2.2 ^2.3 ^2.4 General Motors estimate ↑ ^3.0 ^3.1 General Motors Powertrain

Combined Parallel and Serial Coupled Gearset Concept For More Gears And Improved Cost-Effectiveness

Main Objectives

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 8 to gear 2 in extreme situations simply by changing one shift element (actuating break B and releasing clutch D).^[12]

Extent

In order to increase the number of ratios, ZF and consequently GM have 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 patented gearset concept. The resulting progress is reflected in a better ratio of the number of gears to the number of components used compared to existing layouts. The ZF 8HP has become the new reference standard (benchmark) for automatic transmissions.

Gearset Concept: Cost-Effectiveness^{[lower-alpha 1]}
With Assessment	Output: Gear Ratios	Innovation Elasticity^{[lower-alpha 2]} Δ Output : Δ Input	Input: Main Components
With Assessment	Output: Gear Ratios	Innovation Elasticity^{[lower-alpha 2]} Δ Output : Δ Input	Total	Gearsets	Brakes	Clutches

8L Ref. Object	$n_{O 1}$ $n_{O 2}$	Topic^{[lower-alpha 2]}	$n_{I} = n_{G} +$ $n_{B} + n_{C}$	$n_{G 1}$ $n_{G 2}$	$n_{B 1}$ $n_{B 2}$	$n_{C 1}$ $n_{C 2}$
Δ Number	$n_{O 1} - n_{O 2}$	Topic^{[lower-alpha 2]}	$n_{I 1} - n_{I 2}$	$n_{G 1} - n_{G 2}$	$n_{B 1} - n_{B 2}$	$n_{C 1} - n_{C 2}$
Relative Δ	Δ Output $\frac{n_{O 1} - n_{O 2}}{n_{O 2}}$	$\frac{n_{O 1} - n_{O 2}}{n_{O 2}} : \frac{n_{I 1} - n_{I 2}}{n_{I 2}}$ $= \frac{n_{O 1} - n_{O 2}}{n_{O 2}}$ · $\frac{n_{I 2}}{n_{I 1} - n_{I 2}}$	Δ Input $\frac{n_{I 1} - n_{I 2}}{n_{I 2}}$	$\frac{n_{G 1} - n_{G 2}}{n_{G 2}}$	$\frac{n_{B 1} - n_{B 2}}{n_{B 2}}$	$\frac{n_{C 1} - n_{C 2}}{n_{C 2}}$

8L 6L^{[lower-alpha 3]}	8^{[lower-alpha 4]} 6^{[lower-alpha 4]}	Progress^{[lower-alpha 2]}	9 8	4 3^{[lower-alpha 5]}	2 2	3 3
Δ Number	2	Progress^{[lower-alpha 2]}	1	1	0	0
Relative Δ	0.333 $\frac{1}{3}$	2.667^{[lower-alpha 2]} $\frac{1}{3} : \frac{1}{8} = \frac{1}{3}$ · $\frac{8}{1} = \frac{8}{3}$	0.125 $\frac{1}{8}$	0.333 $\frac{1}{3}$	0.000 $\frac{0}{2}$	0.000 $\frac{0}{3}$

8L ZF 8HP^{[lower-alpha 6]}	8^{[lower-alpha 4]} 8^{[lower-alpha 4]}	Current Market Position^{[lower-alpha 2]}	9 9	4 4	2 2	3 3
Δ Number	0	Current Market Position^{[lower-alpha 2]}	0	0	0	0
Relative Δ	0.000 $\frac{0}{8}$	0.000^{[lower-alpha 2]} $\frac{0}{8} : \frac{0}{9} = \frac{0}{8}$ · $\frac{9}{0} = \frac{0}{0}$	0.000 $\frac{0}{9}$	0.000 $\frac{0}{4}$	0.000 $\frac{0}{2}$	0.000 $\frac{0}{3}$

8L 3-Speed^{[lower-alpha 7]}	8^{[lower-alpha 4]} 3^{[lower-alpha 4]}	Historical Market Position^{[lower-alpha 2]}	9 7	4 2	2 3	3 2
Δ Number	5	Historical Market Position^{[lower-alpha 2]}	2	2	-1	1
Relative Δ	1.667 $\frac{5}{3}$	5.833^{[lower-alpha 2]} $\frac{5}{3} : \frac{2}{7} = \frac{5}{3}$ · $\frac{7}{2} = \frac{35}{6}$	0.286 $\frac{2}{7}$	1.000 $\frac{1}{1}$	−0.333 $\frac{- 1}{3}$	0.500 $\frac{1}{2}$

↑ 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 ↑ ^2.0 ^2.1 ^2.2 ^2.3 ^2.4 ^2.5 ^2.6 ^2.7 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 ↑ ^4.0 ^4.1 ^4.2 ^4.3 ^4.4 ^4.5 plus 1 reverse gear ↑ of which 2 gearsets are combined as a compound Ravigneaux gearset ↑ Current Reference Standard (Benchmark) The 8HP has become the new reference standard (benchmark) for automatic transmissions ↑ 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

Gearset Concept: Quality

The ratios of the 8 gears are relatively unevenly distributed in all versions. Particularly noticeable are the too small step between 3rd and 4th gear and the too large one between 7th and 8th gear. This cannot be eliminated without affecting all other gear ratios. On the other hand the selected gearset concept offers 2 to 3 gears more than conventional transmissions of comparable manufacturing costs, which more than compensates for the weaknesses.

Gear Ratio Analysis^{[lower-alpha 1]}^{[lower-alpha 2]}
In-Depth Analysis^{[lower-alpha 3]} With Assessment And Torque Ratio^{[lower-alpha 4]} And Efficiency Calculation^{[lower-alpha 5]}			Planetary Gearset: Teeth^{[lower-alpha 6]}				Count	Nomi- nal^{[lower-alpha 7]} Effec- tive^{[lower-alpha 8]}	Cen- ter^{[lower-alpha 9]}
			Planetary Gearset: Teeth^{[lower-alpha 6]}				Count	Nomi- nal^{[lower-alpha 7]} Effec- tive^{[lower-alpha 8]}	Avg.^{[lower-alpha 10]}

Model Type	Version First Delivery		S₁^{[lower-alpha 11]} R₁^{[lower-alpha 12]}	S₂^{[lower-alpha 13]} R₂^{[lower-alpha 14]}	S₃^{[lower-alpha 15]} R₃^{[lower-alpha 16]}	S₄^{[lower-alpha 17]} R₄^{[lower-alpha 18]}	Brakes Clutches	Ratio Span	Gear Step^{[lower-alpha 19]}
Gear	R	1	2	3	4	5	6	7	8
Gear Ratio^{[lower-alpha 3]}	$i_{R}$ ^{[lower-alpha 3]}	$i_{1}$ ^{[lower-alpha 3]}	$i_{2}$ ^{[lower-alpha 3]}	$i_{3}$ ^{[lower-alpha 3]}	$i_{4}$ ^{[lower-alpha 3]}	$i_{5}$ ^{[lower-alpha 3]}	$i_{6}$ ^{[lower-alpha 3]}	$i_{7}$ ^{[lower-alpha 3]}	$i_{8}$ ^{[lower-alpha 3]}
Step^{[lower-alpha 19]}	$- \frac{i_{R}}{i_{1}}$ ^{[lower-alpha 20]}	$\frac{i_{1}}{i_{1}}$	$\frac{i_{1}}{i_{2}}$ ^{[lower-alpha 21]}	$\frac{i_{2}}{i_{3}}$	$\frac{i_{3}}{i_{4}}$	$\frac{i_{4}}{i_{5}}$	$\frac{i_{5}}{i_{6}}$	$\frac{i_{6}}{i_{7}}$	$\frac{i_{7}}{i_{8}}$
Δ Step^{[lower-alpha 22]}^{[lower-alpha 23]}			$\frac{i_{1}}{i_{2}} : \frac{i_{2}}{i_{3}}$	$\frac{i_{2}}{i_{3}} : \frac{i_{3}}{i_{4}}$	$\frac{i_{3}}{i_{4}} : \frac{i_{4}}{i_{5}}$	$\frac{i_{4}}{i_{5}} : \frac{i_{5}}{i_{6}}$	$\frac{i_{5}}{i_{6}} : \frac{i_{6}}{i_{7}}$	$\frac{i_{6}}{i_{7}} : \frac{i_{7}}{i_{8}}$
Shaft Speed	$\frac{i_{1}}{i_{R}}$	$\frac{i_{1}}{i_{1}}$	$\frac{i_{1}}{i_{2}}$	$\frac{i_{1}}{i_{3}}$	$\frac{i_{1}}{i_{4}}$	$\frac{i_{1}}{i_{5}}$	$\frac{i_{1}}{i_{6}}$	$\frac{i_{1}}{i_{7}}$	$\frac{i_{1}}{i_{8}}$
Δ Shaft Speed^{[lower-alpha 24]}	$0 - \frac{i_{1}}{i_{R}}$	$\frac{i_{1}}{i_{1}} - 0$	$\frac{i_{1}}{i_{2}} - \frac{i_{1}}{i_{1}}$	$\frac{i_{1}}{i_{3}} - \frac{i_{1}}{i_{2}}$	$\frac{i_{1}}{i_{4}} - \frac{i_{1}}{i_{3}}$	$\frac{i_{1}}{i_{5}} - \frac{i_{1}}{i_{4}}$	$\frac{i_{1}}{i_{6}} - \frac{i_{1}}{i_{5}}$	$\frac{i_{1}}{i_{7}} - \frac{i_{1}}{i_{6}}$	$\frac{i_{1}}{i_{8}} - \frac{i_{1}}{i_{7}}$
Torque Ratio^{[lower-alpha 4]}	$μ_{R}$ ^{[lower-alpha 4]}	$μ_{1}$ ^{[lower-alpha 4]}	$μ_{2}$ ^{[lower-alpha 4]}	$μ_{3}$ ^{[lower-alpha 4]}	$μ_{4}$ ^{[lower-alpha 4]}	$μ_{5}$ ^{[lower-alpha 4]}	$μ_{6}$ ^{[lower-alpha 4]}	$μ_{7}$ ^{[lower-alpha 4]}	$μ_{8}$ ^{[lower-alpha 4]}
Efficiency $η_{n}$ ^{[lower-alpha 5]}	$\frac{μ_{R}}{i_{R}}$ ^{[lower-alpha 5]}	$\frac{μ_{1}}{i_{1}}$ ^{[lower-alpha 5]}	$\frac{μ_{2}}{i_{2}}$ ^{[lower-alpha 5]}	$\frac{μ_{3}}{i_{3}}$ ^{[lower-alpha 5]}	$\frac{μ_{4}}{i_{4}}$ ^{[lower-alpha 5]}	$\frac{μ_{5}}{i_{5}}$ ^{[lower-alpha 5]}	$\frac{μ_{6}}{i_{6}}$ ^{[lower-alpha 5]}	$\frac{μ_{7}}{i_{7}}$ ^{[lower-alpha 5]}	$\frac{μ_{8}}{i_{8}}$ ^{[lower-alpha 5]}

8L 90-M5U 8L 80-MFC 8L 80-N8X	900 N⋅m (664 lb⋅ft)^[9] 2014^{[lower-alpha 25]} · 2023^[5]		41^[13] 79	46 86	37 73	25 89	2 3	6.9991 5.8595 ^{[lower-alpha 8]}^{[lower-alpha 20]}	1.7236
8L 90-M5U 8L 80-MFC 8L 80-N8X	900 N⋅m (664 lb⋅ft)^[9] 2014^{[lower-alpha 25]} · 2023^[5]		41^[13] 79	46 86	37 73	25 89	2 3	6.9991 5.8595 ^{[lower-alpha 8]}^{[lower-alpha 20]}	1.3204^{[lower-alpha 19]}
Gear	R	1	2	3	4	5	6	7	8
Gear Ratio^{[lower-alpha 3]}	−3.8176 ^{[lower-alpha 20]}^{[lower-alpha 8]} $- \frac{43, 043}{11, 275}$	4.5600 $\frac{114}{25}$	2.9709^{[lower-alpha 23]} $\frac{817}{275}$	2.0751 $\frac{12, 540}{6, 043}$	1.6876 ^{[lower-alpha 19]}^{[lower-alpha 23]}^{[lower-alpha 24]} $\frac{4, 121}{2, 442}$	1.2700^{[lower-alpha 23]} $\frac{28, 817, 100}{22, 690, 429}$	1.0000 $\frac{1}{1}$	0.8455 ^{[lower-alpha 23]}^{[lower-alpha 24]} $\frac{5, 160}{6, 103}$	0.6515 $\frac{43}{66}$
Step	0.8372^{[lower-alpha 20]}	1.0000	1.5349	1.4317	1.2297^{[lower-alpha 19]}	1.3288	1.2700	1.1828	1.2977
Δ Step^{[lower-alpha 22]}			1.0721^{[lower-alpha 23]}	1.1643	0.9254^{[lower-alpha 23]}	1.0463^{[lower-alpha 23]}	1.0738	0.9114^{[lower-alpha 23]}
Speed	-1.1945	1.0000	1.5349	2.1975	2.7021	3.5905	4.56	5.3933	6.9991
Δ Speed	1.1945	1.0000	0.5349	0.6626	0.5047^{[lower-alpha 24]}	0.8884	0.9695	0.8333^{[lower-alpha 24]}	1.6057
Torque Ratio^{[lower-alpha 4]}	–3.6149 –3.5155	4.48887 4.4532	2.9039 2.8704	2.0535 2.0255	1.6650 1.6385	1.2578 1.2516	1.0000	0.8411 0.8409	0.6469 0.6446
Efficiency $η_{n}$ ^{[lower-alpha 5]}	0.9469 0.9209	0.9844 0.9766	0.9774 0.9662	0.9896 0.9761	0.9866 0.9709	0.9904 0.9855	1.0000	0.9948 0.9945	0.9929 0.9893

8L 45 M5N	550 N⋅m (406 lb⋅ft) 2015^{[lower-alpha 26]} · 2023^[6]		41 79	41 79	41 79	26 94	2 3	7.0107 5.9662 ^{[lower-alpha 8]}^{[lower-alpha 20]}	1.7431
8L 45 M5N	550 N⋅m (406 lb⋅ft) 2015^{[lower-alpha 26]} · 2023^[6]		41 79	41 79	41 79	26 94	2 3	7.0107 5.9662 ^{[lower-alpha 8]}^{[lower-alpha 20]}	1.3208^{[lower-alpha 19]}
Gear	R	1	2	3	4	5	6	7	8
Gear Ratio^{[lower-alpha 3]}	−3.9278 ^{[lower-alpha 20]}^{[lower-alpha 8]} $- \frac{4, 187}{1, 066}$	4.6154 $\frac{60}{13}$	3.0385^{[lower-alpha 23]} $\frac{79}{26}$	2.0648 $\frac{7, 200}{3, 487}$	1.6583 ^{[lower-alpha 19]}^{[lower-alpha 23]}^{[lower-alpha 24]} $\frac{199}{120}$	1.2587^{[lower-alpha 23]} $\frac{740, 760}{588, 527}$	1.0000 $\frac{1}{1}$	0.8494 ^{[lower-alpha 23]}^{[lower-alpha 24]} $\frac{9, 480}{11, 161}$	0.6583 $\frac{79}{120}$
Step	0.8510^{[lower-alpha 20]}	1.0000	1.5190	1.4715	1.2451^{[lower-alpha 19]}	1.3175	1.2587	1.1773	1.2902
Δ Step^{[lower-alpha 22]}			1.0322^{[lower-alpha 23]}	1.1819	0.9450^{[lower-alpha 23]}	1.0468^{[lower-alpha 23]}	1.0691	0.9125^{[lower-alpha 23]}
Speed	-1.1751	1.0000	1.5190	2.2353	2.7831	3.6669	4.6154	5.4338	7.0107
Δ Speed	1.1751	1.0000	0.5190	0.7163	0.5479^{[lower-alpha 24]}	0.8837	0.9485	0.8184^{[lower-alpha 24]}	1.5769
Torque Ratio^{[lower-alpha 4]}	–3.7202 –3.6185	4.5431 4.5069	2.9701 2.9360	2.0435 2.0328	1.6366 1.6258	1.2468 1.2408	1.0000	0.8451 0.8428	0.6538 0.6514
Efficiency $η_{n}$ ^{[lower-alpha 5]}	0.9472 0.9213	0.9843 0.9765	0.9775 0.9663	0.9897 0.9845	0.9869 0.9804	0.9905 0.9858	1.0000	0.9949 0.9923	0.9931 0.9895

Actuated Shift Elements^{[lower-alpha 27]}
Brake A^{[lower-alpha 28]}	❶	❶	❶					❶	❶
Brake B^{[lower-alpha 29]}	❶	❶	❶	❶	❶	❶
Clutch C^{[lower-alpha 30]}		❶		❶		❶	❶	❶
Clutch D^{[lower-alpha 31]}	❶				❶	❶	❶	❶	❶
Clutch E^{[lower-alpha 32]}			❶	❶	❶		❶		❶
Geometric Ratios: Speed Conversion
Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 33]} R & 1 & 2 Ordinary^{[lower-alpha 34]} Elementary Noted^{[lower-alpha 35]}	$i_{R} = \frac{R_{2} (S_{1} S_{4} - R_{1} R_{4})}{S_{1} S_{4} (S_{2} + R_{2})}$			$i_{1} = \frac{S_{4} + R_{4}}{S_{4}}$			$i_{2} = \frac{R_{2} (S_{4} + R_{4})}{(S_{2} + R_{2}) S_{4}}$
	$i_{R} = \frac{1 - \frac{R_{1} R_{4}}{S_{1} S_{4}}}{1 + \frac{S_{2}}{R_{2}}}$			$i_{1} = 1 + \frac{R_{4}}{S_{4}}$			$i_{2} = \frac{1 + \frac{R_{4}}{S_{4}}}{1 + \frac{S_{2}}{R_{2}}}$

Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 33]} 3 & 4 Ordinary^{[lower-alpha 34]} Elementary Noted^{[lower-alpha 35]}	$i_{3} = \frac{(S_{3} + R_{3}) (S_{4} + R_{4})}{S_{4} R_{3} + S_{3} (S_{4} + R_{4})}$					$i_{4} = 1 + \frac{S_{2} R_{3}}{S_{3} (S_{2} + R_{2})}$
	$i_{3} = \frac{1}{\frac{1}{1 + \frac{R_{3}}{S_{3}}} + \frac{1}{(1 + \frac{S_{3}}{R_{3}}) (1 + \frac{R_{4}}{S_{4}})}}$					$i_{4} = 1 + \frac{\frac{R_{3}}{S_{3}}}{1 + \frac{R_{2}}{S_{2}}}$

Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 33]} 5 Ordinary^{[lower-alpha 34]} Elementary Noted^{[lower-alpha 35]}	$i_{5} = \frac{S_{3} R_{2} R_{4} (S_{1} + R_{1}) + S_{2} S_{1} (S_{3} + R_{3}) (S_{4} + R_{4})}{S_{3} R_{4} (S_{1} (S_{2} + R_{2}) + R_{1} R_{2}) + S_{1} S_{2} S_{4} (S_{3} + R_{3})}$
	$i_{5} = \frac{1}{\frac{1}{\frac{(1 + \frac{R_{3}}{S_{3}}) (1 + \frac{S_{4}}{R_{4}})}{1 + \frac{R_{2}}{S_{2}} (1 + \frac{R_{1}}{S_{1}})} + \frac{1}{\frac{1}{1 + \frac{S_{1}}{R_{1}}} + \frac{1 + \frac{S_{2}}{R_{2}}}{1 + \frac{R_{1}}{S_{1}}}}} + \frac{1}{1 + \frac{R_{4}}{S_{4}} + \frac{\frac{R_{2} R_{4}}{S_{2} S_{4}} (1 + \frac{R_{1}}{S_{1}})}{1 + \frac{R_{3}}{S_{3}}}}}$

Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 33]} 6 – 8 Ordinary^{[lower-alpha 34]} Elementary Noted^{[lower-alpha 35]}	$i_{6} = \frac{1}{1}$		$i_{7} = \frac{R_{2} (S_{1} + R_{1})}{R_{2} (S_{1} + R_{1}) + S_{1} S_{2}}$				$i_{8} = \frac{R_{2}}{S_{2} + R_{2}}$
	$i_{6} = \frac{1}{1}$		$i_{7} = \frac{1}{1 + \frac{\frac{S_{2}}{R_{2}}}{1 + \frac{R_{1}}{S_{1}}}}$				$i_{8} = \frac{1}{1 + \frac{S_{2}}{R_{2}}}$
Kinetic Ratios: Torque Conversion
Torque Ratio^{[lower-alpha 4]} R & 1 & 2	$μ_{R} = \frac{1 - \frac{R_{1} R_{4}}{S_{1} S_{4}} {η_{0}}^{2}}{1 + \frac{S_{2}}{R_{2}} \cdot \frac{1}{η_{0}}}$			$μ_{1} = 1 + \frac{R_{4}}{S_{4}} η_{0}$			$μ_{2} = \frac{1 + \frac{R_{4}}{S_{4}} η_{0}}{1 + \frac{S_{2}}{R_{2}} \cdot \frac{1}{η_{0}}}$

Torque Ratio^{[lower-alpha 4]} 3 & 4	$μ_{3} = \frac{1}{\frac{1}{1 + \frac{R_{3}}{S_{3}} {η_{0}}^{\frac{1}{2}}} + \frac{1}{(1 + \frac{S_{3}}{R_{3}} {η_{0}}^{\frac{1}{2}}) (1 + \frac{R_{4}}{S_{4}} η_{0})}}$					$μ_{4} = 1 + \frac{\frac{R_{3}}{S_{3}} η_{0}}{1 + \frac{R_{2}}{S_{2}} \cdot \frac{1}{η_{0}}}$

Torque Ratio^{[lower-alpha 4]} 5	$μ_{5} = \frac{1}{\frac{1}{\frac{(1 + \frac{R_{3}}{S_{3}} {η_{0}}^{\frac{1}{2}}) (1 + \frac{S_{4}}{R_{4}} {η_{0}}^{\frac{1}{3}})}{1 + \frac{R_{2}}{S_{2}} \cdot \frac{1}{{η_{0}}^{\frac{1}{3}}} (1 + \frac{R_{1}}{S_{1}} \cdot \frac{1}{{η_{0}}^{\frac{1}{4}}})} + \frac{1}{\frac{1}{1 + \frac{S_{1}}{R_{1}} {η_{0}}^{\frac{1}{4}}} + \frac{1 + \frac{S_{2}}{R_{2}} \cdot \frac{1}{{η_{0}}^{\frac{1}{3}}}}{1 + \frac{R_{1}}{S_{1}} {η_{0}}^{\frac{1}{4}}}}} + \frac{1}{1 + \frac{R_{4}}{S_{4}} {η_{0}}^{\frac{1}{3}} + \frac{\frac{R_{2} R_{4}}{S_{2} S_{4}} {η_{0}}^{\frac{2}{3}} (1 + \frac{R_{1}}{S_{1}} {η_{0}}^{\frac{1}{4}})}{1 + \frac{R_{3}}{S_{3}} \cdot \frac{1}{{η_{0}}^{\frac{1}{2}}}}}}$

Torque Ratio^{[lower-alpha 4]} 6 – 8	$μ_{6} = \frac{1}{1}$		$μ_{7} = \frac{1}{1 + \frac{\frac{S_{2}}{R_{2}} \cdot \frac{1}{η_{0}}}{1 + \frac{R_{1}}{S_{1}} η_{0}}}$				$μ_{8} = \frac{1}{1 + \frac{S_{2}}{R_{2}} \cdot \frac{1}{η_{0}}}$

8HP70 ^{[lower-alpha 36]}^{[lower-alpha 37]}	700 N⋅m (516 lb⋅ft) 2008		48^[14] 96	48^[14] 96	69^[2] 111	23^[2] 85	2 3	7.0435 4.9452 ^{[lower-alpha 8]}^{[lower-alpha 20]}	1.7693
8HP70 ^{[lower-alpha 36]}^{[lower-alpha 37]}	700 N⋅m (516 lb⋅ft) 2008		48^[14] 96	48^[14] 96	69^[2] 111	23^[2] 85	2 3	7.0435 4.9452 ^{[lower-alpha 8]}^{[lower-alpha 20]}	1.3216^{[lower-alpha 19]}
Gear	R	1	2	3	4	5	6	7	8
Gear Ratio^{[lower-alpha 3]}	−3.2968 ^{[lower-alpha 20]}^{[lower-alpha 8]} $- \frac{1, 744}{529}$	4.6957 $\frac{108}{23}$	3.1304^{[lower-alpha 23]} $\frac{72}{23}$	2.1039 $\frac{162}{77}$	1.6667 ^{[lower-alpha 19]}^{[lower-alpha 23]}^{[lower-alpha 24]} $\frac{5}{3}$	1.2845^{[lower-alpha 23]} $\frac{8, 826}{6, 871}$	1.0000 $\frac{1}{1}$	0.8392 ^{[lower-alpha 23]}^{[lower-alpha 24]} $\frac{120}{143}$	0.6667 $\frac{2}{3}$
Step	0.7021^{[lower-alpha 20]}	1.0000	1.5000	1.4879	1.2623^{[lower-alpha 19]}	1.2975	1.2845	1.1917	1.2587
Δ Step^{[lower-alpha 22]}			1.0081^{[lower-alpha 23]}	1.1787	0.9729^{[lower-alpha 23]}	1.0101^{[lower-alpha 23]}	1.0779	0.9467^{[lower-alpha 23]}
Speed	-1.4243	1.0000	1.5000	2.2319	2.8174	3.6555	4.6957	5.5965	7.0435
Δ Speed	1.4243	1.0000	0.5000	0.7319	0.5855^{[lower-alpha 24]}	0.8382	1.0401	0.9000^{[lower-alpha 24]}	1.4478
Torque Ratio^{[lower-alpha 4]}	–3.1186 –3.0313	4.6217 4.5848	3.0603 3.0253	2.0820 2.0709	1.6446 1.6336	1.2720 1.2658	1.0000	0.8347 0.8324	0.6622 0.6599
Efficiency $η_{n}$ ^{[lower-alpha 5]}	0.9460 0.9195	0.9843 0.9764	0.9776 0.9664	0.9896 0.9843	0.9867 0.9802	0.9903 0.9854	1.0000	0.9947 0.9920	0.9932 0.9898

Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 38]} R & 1 & 2	$i_{R} = \frac{R_{2} (S_{3} S_{4} - R_{3} R_{4})}{S_{3} S_{4} (S_{2} + R_{2})}$			$i_{1} = \frac{S_{4} + R_{4}}{S_{4}}$			$i_{2} = \frac{R_{2} (S_{4} + R_{4})}{(S_{2} + R_{2}) S_{4}}$

Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 38]} 3 & 4	$i_{3} = \frac{(S_{1} + R_{1}) (S_{4} + R_{4})}{S_{4} R_{1} + S_{1} (S_{4} + R_{4})}$					$i_{4} = 1 + \frac{S_{2} R_{1}}{S_{1} (S_{2} + R_{2})}$

Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 38]} 5	$i_{5} = \frac{S_{1} R_{2} R_{4} (S_{3} + R_{3}) + S_{2} S_{3} (S_{1} + R_{1}) (S_{4} + R_{4})}{S_{1} R_{4} (S_{3} (S_{2} + R_{2}) + R_{2} R_{3}) + S_{2} S_{3} S_{4} (S_{1} + R_{1})}$

Gear Ratio^{[lower-alpha 3]}^{[lower-alpha 38]} 6 – 8	$i_{6} = \frac{1}{1}$		$i_{7} = \frac{R_{2} (S_{3} + R_{3})}{R_{2} (S_{3} + R_{3}) + S_{2} S_{3}}$				$i_{8} = \frac{R_{2}}{S_{2} + R_{2}}$

↑ All 8L-transmissions are based on a dedicated 8-speed layout, first realized in the ZF 8HP 70 gearbox ↑ Revised 14 January 2026 Nomenclature $S_{n} =$ sun gear: number of teeth $R_{n} =$ ring gear: number of teeth $C_{n} =$ carrier or planetary gear carrier (not needed) $s_{n} =$ sun gear: shaft speed $r_{n} =$ ring gear: shaft speed $c_{n} =$ carrier or planetary gear carrier: shaft speed With $n =$ gear is $i_{n} =$ gear ratio or transmission ratio $ω_{1; n} = ω_{t} =$ shaft speed shaft 1: input (turbine) shaft $ω_{2; n} =$ shaft speed shaft 2: output shaft $T_{1; n} = T_{t} =$ torque shaft 1: input (turbine) shaft $T_{2; n} =$ torque shaft 2: output shaft $μ_{n} =$ torque ratio or torque conversion ratio $η_{n} =$ efficiency $i_{0} =$ stationary gear ratio $η_{0} =$ (assumed) stationary gear efficiency ↑ ^3.00 ^3.01 ^3.02 ^3.03 ^3.04 ^3.05 ^3.06 ^3.07 ^3.08 ^3.09 ^3.10 ^3.11 ^3.12 ^3.13 ^3.14 ^3.15 ^3.16 ^3.17 ^3.18 ^3.19 ^3.20 ^3.21 Gear Ratio (Transmission Ratio) $i_{n}$ — Speed Conversion — The gear ratio $i_{n}$ is the ratio of input shaft speed $ω_{1; n}$ to output shaft speed $ω_{2; n}$ and therefore corresponds to the reciprocal of the shaft speeds $i_{n} = \frac{1}{\frac{ω_{2; n}}{ω_{1; n}}} = \frac{ω_{1; n}}{ω_{2; n}} = \frac{ω_{t}}{ω_{2; n}}$ ↑ ^4.00 ^4.01 ^4.02 ^4.03 ^4.04 ^4.05 ^4.06 ^4.07 ^4.08 ^4.09 ^4.10 ^4.11 ^4.12 ^4.13 ^4.14 ^4.15 ^4.16 ^4.17 Torque Ratio (Torque Conversion Ratio) $μ_{n}$ — Torque Conversion — The torque ratio $μ_{n}$ is the ratio of output torque $T_{2; n}$ to input torque $T_{1; n}$ minus efficiency losses and therefore corresponds (apart from the efficiency losses) to the reciprocal of the shaft speeds too $μ_{n} = i_{n} η_{n; η_{0}} = \frac{ω_{1; n} η_{n; η_{0}}}{ω_{2; n}} = \frac{T_{2; n} η_{n; η_{0}}}{T_{1; n}}$ whereby $η_{n; η_{0}}$ may vary from gear to gear according to the formulas listed in this table and $0 \leq η_{n; η_{0}} \leq 1$ ↑ ^5.00 ^5.01 ^5.02 ^5.03 ^5.04 ^5.05 ^5.06 ^5.07 ^5.08 ^5.09 ^5.10 ^5.11 ^5.12 ^5.13 Efficiency The efficiency $η_{n}$ is calculated from the torque ratio in relation to the gear ratio (transmission ratio) $η_{n} = \frac{μ_{n}}{i_{n}}$ 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, the stationary gear ratio $i_{0}$ 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 $η_{0}$ specified here are based on assumed efficiencies for the stationary ratio $i_{0}$ of $η_{0} = 0.9800$ (upper value) and $η_{0} = 0.9700$ (lower value) for both interventions together The corresponding efficiency for single-meshing gear pairs is ${η_{0}}^{\frac{1}{2}}$ at $0.980 0^{\frac{1}{2}} = 0.98995$ (upper value) and $0.970 0^{\frac{1}{2}} = 0.98489$ (lower value) ↑ Layout Input and output are on opposite sides Planetary gearset 1 is on the input (turbine) side Input (turbine) shafts are C₂ and, if actuated, R₃ and S₄ Output shaft is C₄ ↑ Total Ratio Span (Total Gear/Transmission Ratio) Nominal $\frac{ω_{2; n}}{ω_{2; 1}} = \frac{\frac{ω_{2; n}}{ω_{2; 1} ω_{2; n}}}{\frac{ω_{2; 1}}{ω_{2; 1} ω_{2; n}}} = \frac{\frac{1}{ω_{2; 1}}}{\frac{1}{ω_{2; n}}} = \frac{\frac{ω_{t}}{ω_{2; 1}}}{\frac{ω_{t}}{ω_{2; n}}} = \frac{i_{1}}{i_{n}}$ 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 ↑ ^8.0 ^8.1 ^8.2 ^8.3 ^8.4 ^8.5 ^8.6 Total Ratio Span (Total Gear Ratio/Total Transmission Ratio) Effective $\frac{ω_{2; n}}{m a x (ω_{2; 1}; \| ω_{2; R} \|)} = \frac{m i n (i_{1}; \| i_{R} \|)}{i_{n}}$ The span is only effective to the extent that the reverse gear ratio matches that of 1st gear see also Standard R:1 Digression Reverse gear is usually longer than 1st gear the effective span* is therefore of central importance for describing the suitability of a transmission* because in these cases, the nominal 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 the effective span* has therefore not yet been able to establish itself* either in theory or in practice. End of digression ↑ Ratio Span's Center $(i_{1} i_{n})^{\frac{1}{2}}$ 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 ${(\frac{ω_{2; n}}{ω_{2; 1}})}^{\frac{1}{n - 1}} = {(\frac{i_{1}}{i_{n}})}^{\frac{1}{n - 1}}$ There are $n - 1$ gear steps between $n$ gears 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 ↑ Ring 2: ring gear of gearset 2 ↑ Sun 3: sun gear of gearset 3 ↑ Ring 3: ring gear of gearset 3 ↑ Sun 4: sun gear of gearset 4 ↑ Ring 4: ring gear of gearset 4 ↑ ^19.00 ^19.01 ^19.02 ^19.03 ^19.04 ^19.05 ^19.06 ^19.07 ^19.08 ^19.09 ^19.10 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 3) is always larger and the upper half of the gear steps (between the large gears; rounded up, here the last 4) 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) ↑ ^20.00 ^20.01 ^20.02 ^20.03 ^20.04 ^20.05 ^20.06 ^20.07 ^20.08 ^20.09 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 ↑ 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) ↑ ^22.0 ^22.1 ^22.2 ^22.3 From large to small gears (from right to left) ↑ ^23.00 ^23.01 ^23.02 ^23.03 ^23.04 ^23.05 ^23.06 ^23.07 ^23.08 ^23.09 ^23.10 ^23.11 ^23.12 ^23.13 ^23.14 ^23.15 ^23.16 ^23.17 ^23.18 ^23.19 ^23.20 ^23.21 ^23.22 ^23.23 ^23.24 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) ↑ ^24.00 ^24.01 ^24.02 ^24.03 ^24.04 ^24.05 ^24.06 ^24.07 ^24.08 ^24.09 ^24.10 ^24.11 ^24.12 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) ↑ Model year 2015 ↑ Model year 2016 ↑ Permanently coupled elements S₁ and R₂ C₁ and C₄ S₂ and S₃ C₃ and R₄ ↑ Blocks S₂ and S₃ ↑ Blocks R₃ ↑ Couples C₂ and S₄ with the input (turbine) ↑ Couples R₁ with S₄ ↑ Couples S₁ and R₂ with S₄ ↑ ^33.0 ^33.1 ^33.2 ^33.3 Adjusted formulas with gearset 1 and 3 swapped ↑ ^34.0 ^34.1 ^34.2 ^34.3 Ordinary Noted For direct determination of the gear ratio ↑ ^35.0 ^35.1 ^35.2 ^35.3 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 ↑ without generation designation ↑ First transmission on the market to use the dedicated 8-speed layout gearset 1 and 3 not swapped for comparison purposes only ↑ ^38.0 ^38.1 ^38.2 ^38.3 Original formulas gearset 1 and 3 not swapped for comparison purposes only

Applications

Variants And Applications
Make	Model Years	Model	Final Drive Ratio

8L 90
Cadillac	2015–2017	Escalade^[15]	3.23
	2016–present	ATS-V	2.85
	2016–present	CTS-V	2.85
	2016–present	CT6	3.27
Chevrolet	2015–2019	Corvette (C7) Stingray^[16]	2.41^{[lower-alpha 1]} or 2.73^{[lower-alpha 2]}
	2015–2019	Corvette (C7) Z06^[17]	2.41
	2019	Corvette (C7) ZR1	2.73
	2015–present	Silverado^[18]	3.23^{[lower-alpha 1]} or 3.42^{[lower-alpha 3]}
	2015–present	Colorado	3.42
	2016–2018	Camaro SS	2.77
	2017–present	Express^{[lower-alpha 4]}
GMC	2015–2017	Yukon Denali · Denali XL	3.23
	2015–present	Sierra^[18]	3.23
	2015–present	Canyon	3.42
8L 80
Chevrolet	2023–present	Colorado
Chevrolet	2024–present	Silverado
GMC	2023–present	Canyon
8L 45
Cadillac	2016–2019	ATS
	2016–2019	CTS
	2020–present	CT4
	2016–present	CT6
Chevrolet	2016–2023	Camaro LT (2.0L)	3.27
	2016–2019	Camaro LT (3.6L)	2.77
	2017–present	Colorado	3.42
GMC	2017–present	Canyon

↑ ^1.0 ^1.1 Standard ↑ Z51 ↑ Maximum Trailering Package ↑ 2.8 L diesel engine and 4.3 L gas engine only

Lawsuits and issues

8L 45 and 8L 90 transmissions manufactured between 2015 and 2019 suffer from two different, unrelated problems.^[19] The first is that the 8L’s transmission fluid can absorb moisture from the air via the vent system, especially in humid climates, which can cause the clutches to slip. This can cause some customers, especially those driving in high gears, to feel a “shake/shudder feeling” akin to driving over rumble strips or rough pavement.^[19] Introduction of moisture-resistant transmission fluid in December 2018 largely resolved this issue.^[19] The second issue is that when changing gears 8L transmissions sometimes apply too much pressure and fail to purge trapped air leaking into the valves. This issue can cause jerkiness or hard shifting when upshifting or downshifting, and other issues.^[19] This issue was resolved with the redesigned gen II transmissions, but cannot be repaired on affected transmissions.

These issues are the subject of a class-action lawsuit filed in December 2018 that alleges the transmission suffers from persistent "shudder" issues and that GM has known about the problems since its introduction and has failed to provide a solution, instead choosing to wait until the unit is out of warranty.^[20] As of 2025, the class action had been remanded to the district court for procedural issues.^[19]

References

↑ "US Patent 8,105,196 B2: Automatic Transmission Gear And Clutch Arrangement". US Patent Office. 31 January 2012. https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US8105196.pdf.
↑ ^2.0 ^2.1 ^2.2 Apakidze, Timur (11 March 2014). "Saturation Dive: ZF 8-Speed Automatic". TTAC: The Truth About Cars · Pt. 1. https://www.thetruthaboutcars.com/2014/03/saturation-dive-zf-8-speed-automatic/. and "loc. cit. · Pt. 2". 23 April 2014. https://www.thetruthaboutcars.com/2014/04/saturation-dive-zf-8-speed-automatic/.
↑ ^3.0 ^3.1 "USA Information Guide Model Year 2018". https://www.gmpowertrain.com/assets/docs/2018R_F3F_Information_Guide_031918.pdf.
↑ "Cadillac Introduces New 8-Speed Automatic on CT6". Cadillac Media USA. 20 March 2015. http://media.cadillac.com/media/us/en/cadillac/news.detail.html/content/Pages/news/us/en/2015/mar/0320-cadillac/0320-cadillac-8spd-trans.html.
↑ ^5.0 ^5.1 ^5.2 Regular production option
↑ ^6.0 ^6.1 "Gears Magazine - What's That Noise? GM 8-Speed Generation II" (in en-US). https://gearsmagazine.com/magazine/whats-that-noise-gm-8-speed-generation-ii/.
↑ "Gears Magazine - What's That Noise? GM 8-Speed Generation II" (in en-US). https://gearsmagazine.com/magazine/whats-that-noise-gm-8-speed-generation-ii/.
↑ "New 8-Speed Enables Quicker, More Efficient Corvette". General Motors. 20 August 2014. http://www.gm.com/article.content_pages_news_us_en_2014_aug_0820-8speed_0820-corvette-8-speed-lead.html.
↑ ^9.0 ^9.1 "Transmission Repair Cost Guide". https://www.transmissionrepaircostguide.com/8l90/.
↑ "8L45 8-Speed GM OEM Transmission | GM Powered Solutions". https://poweredsolutions.gm.com/products/8L45-8-speed-transmission/.
↑ "8L90 8-Speed Automatic Transmission | GM Powered Solutions". https://poweredsolutions.gm.com/products/8l90-8-speed-transmission/.
↑ "Maximum driving enjoyment with maximum agility". ZF Friedrichshafen AG. http://www.zf.com/corporate/en/products/innovations/8hp_automatic_transmissions/more_driving_enjoyment/more_driving_enjoyment.html.
↑ "WIT · Whatever It Takes · Automatic Transmission Parts Catalog 2018+2019 Page 268". https://www.wittrans.com/catalog.
↑ ^14.0 ^14.1 8HP 70 Repair Manual · Picture 10106 p. 110 · Saarbruecken 2014 · https://avtgr.ru/upload/data/pdf/zf_instructions/8HP70.pdf
↑ "2015 Cadillac Escalade Updated with 8L 90 8-Speed Automatic and More Tech [Photo Gallery"]. 11 August 2014. http://www.autoevolution.com/news/2015-cadillac-escalade-updated-with-8l 90-8-speed-automatic-and-more-tech-photo-gallery-85117.html.
↑ "Chevrolet Confirms 2015 Corvette Stingray To Utilize 8L 90 Eight-Speed Gearbox". http://gmauthority.com/blog/2014/04/chevrolet-confirms-2015-corvette-stingray-to-utilize-8l90-eight-speed-gearbox/.
↑ "Supercharged 2015 Chevy Corvette Z06 takes the C7 beyond the ZR1 [w/video"]. http://www.autoblog.com/2014/01/13/2015-chevy-corvette-z06-detroit-2014/.
↑ ^18.0 ^18.1 "GM confirms 2015 Silverado, Sierra to get 8-speed automatic". http://www.autoblog.com/2014/07/18/2015-chevy-silverado-gmc-sierra-8-speed-automatic/.
↑ ^19.0 ^19.1 ^19.2 ^19.3 ^19.4 https://www.opn.ca6.uscourts.gov/opinions.pdf/25a0170p-06.pdf This article incorporates public domain text from this source.
↑ "Class Action Lawsuit Filed Over Alleged Shifting Defect in Certain General Motors Transmissions". 19 December 2018. https://www.classaction.org/news/class-action-lawsuit-filed-over-alleged-shifting-defect-in-certain-general-motors-transmissions.

External links

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Original source: https://en.wikipedia.org/wiki/GM 8L transmission. Read more

[8] Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage

[Forward-10] 2.0 ^2.1 Forward gears only

[11] Longitudinal engine

[13] rst transmission to use this 8-speed gearset concept. It has become the new benchmark for automatic transmissions

[14] Hydraulic torque converter · German: Hydraulischer Wandler oder Drehmomentwandler

[15] Planetary gearing · German: Planetenradsätze

[ShortBed-18] 1.0 ^1.1 ^1.2 ^1.3 ^1.4 based on 2020 Chevrolet Colorado Z71 2WD Crew Cab · Short Bed

[Estimate-19] 2.0 ^2.1 ^2.2 ^2.3 ^2.4 General Motors estimate

[GMPT-20] 3.0 ^3.1 General Motors Powertrain

[22] 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

[11] parallel: using the two degrees of freedom of planetary gearsets
to increase the number of gears

with unchanged number of components

[12] to increase the number of gears

[13] with unchanged number of components

[14] 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

[15] to increase the number of gears

[16] rresponding increase in the number of components is unavoidable

[Progress-23] 2.0 ^2.1 ^2.2 ^2.3 ^2.4 ^2.5 ^2.6 ^2.7 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)

[18] 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

[19] 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

[20] 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)

[21] negative, if the output increases and the input decreases, is perfect

[22] 2 or above is good

[23] 1 or above is acceptable (red)

[24] below this is unsatisfactory (bold)

[24] Direct Predecessor
To reflect the progress of the specific model change

[26] To reflect the progress of the specific model change

[Rev-25] 4.0 ^4.1 ^4.2 ^4.3 ^4.4 ^4.5 plus 1 reverse gear

[26] which 2 gearsets are combined as a compound Ravigneaux gearset

[27] Current Reference Standard (Benchmark)
The 8HP has become the new reference standard (benchmark) for automatic transmissions

[30] The 8HP has become the new reference standard (benchmark) for automatic transmissions

[28] 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

[32] 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

[33] 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

[34] 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

[35] All transmission variants consist of 7 main components

[36] 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

[37] Turbo-Hydramatic from GM

[38] Cruise-O-Matic from Ford

[39] TorqueFlite from Chrysler

[40] Detroit Gear from BorgWarner for Studebaker

[41] BW-35 from BorgWarner and as T35 from Aisin

[42] 3N 71 from Nissan/Jatco

[43] 3 HP from ZF Friedrichshafen

[44] W3A 040 and W3B 050 from Mercedes-Benz

[29] All 8L-transmissions are based on a dedicated 8-speed layout, first realized in the ZF 8HP 70 gearbox

[30] Revised 14 January 2026
Nomenclature
$S_{n} =$ sun gear: number of teeth

$R_{n} =$ ring gear: number of teeth

$C_{n} =$ carrier or planetary gear carrier (not needed)

$s_{n} =$ sun gear: shaft speed

$r_{n} =$ ring gear: shaft speed

$c_{n} =$ carrier or planetary gear carrier: shaft speed
With $n =$ gear is
$i_{n} =$ gear ratio or transmission ratio

$ω_{1; n} = ω_{t} =$ shaft speed shaft 1: input (turbine) shaft

$ω_{2; n} =$ shaft speed shaft 2: output shaft

$T_{1; n} = T_{t} =$ torque shaft 1: input (turbine) shaft

$T_{2; n} =$ torque shaft 2: output shaft

$μ_{n} =$ torque ratio or torque conversion ratio

$η_{n} =$ efficiency

$i_{0} =$ stationary gear ratio

$η_{0} =$ (assumed) stationary gear efficiency

[47] $S_{n} =$ sun gear: number of teeth

[48] $R_{n} =$ ring gear: number of teeth

[49] $C_{n} =$ carrier or planetary gear carrier (not needed)

[50] $s_{n} =$ sun gear: shaft speed

[51] $r_{n} =$ ring gear: shaft speed

[52] $c_{n} =$ carrier or planetary gear carrier: shaft speed

[53] $i_{n} =$ gear ratio or transmission ratio

[54] $ω_{1; n} = ω_{t} =$ shaft speed shaft 1: input (turbine) shaft

[55] $ω_{2; n} =$ shaft speed shaft 2: output shaft

[56] $T_{1; n} = T_{t} =$ torque shaft 1: input (turbine) shaft

[57] $T_{2; n} =$ torque shaft 2: output shaft

[58] $μ_{n} =$ torque ratio or torque conversion ratio

[59] $η_{n} =$ efficiency

[60] $i_{0} =$ stationary gear ratio

[61] $η_{0} =$ (assumed) stationary gear efficiency

[Gear_Ratio-31] 3.00 ^3.01 ^3.02 ^3.03 ^3.04 ^3.05 ^3.06 ^3.07 ^3.08 ^3.09 ^3.10 ^3.11 ^3.12 ^3.13 ^3.14 ^3.15 ^3.16 ^3.17 ^3.18 ^3.19 ^3.20 ^3.21 Gear Ratio (Transmission Ratio) $i_{n}$
— Speed Conversion —
The gear ratio $i_{n}$ is the ratio of
input shaft speed $ω_{1; n}$

to output shaft speed $ω_{2; n}$

and therefore corresponds to the reciprocal of the shaft speeds
$i_{n} = \frac{1}{\frac{ω_{2; n}}{ω_{1; n}}} = \frac{ω_{1; n}}{ω_{2; n}} = \frac{ω_{t}}{ω_{2; n}}$

[63] The gear ratio $i_{n}$ is the ratio of
input shaft speed $ω_{1; n}$

to output shaft speed $ω_{2; n}$

[64] ut shaft speed $ω_{1; n}$

[65] to output shaft speed $ω_{2; n}$

[66] therefore corresponds to the reciprocal of the shaft speeds
$i_{n} = \frac{1}{\frac{ω_{2; n}}{ω_{1; n}}} = \frac{ω_{1; n}}{ω_{2; n}} = \frac{ω_{t}}{ω_{2; n}}$

[67] $i_{n} = \frac{1}{\frac{ω_{2; n}}{ω_{1; n}}} = \frac{ω_{1; n}}{ω_{2; n}} = \frac{ω_{t}}{ω_{2; n}}$

[Torque_Ratio-32] 4.00 ^4.01 ^4.02 ^4.03 ^4.04 ^4.05 ^4.06 ^4.07 ^4.08 ^4.09 ^4.10 ^4.11 ^4.12 ^4.13 ^4.14 ^4.15 ^4.16 ^4.17 Torque Ratio (Torque Conversion Ratio) $μ_{n}$
— Torque Conversion —
The torque ratio $μ_{n}$ is the ratio of
output torque $T_{2; n}$

to input torque $T_{1; n}$

minus efficiency losses

and therefore corresponds (apart from the efficiency losses) to the reciprocal of the shaft speeds too
$μ_{n} = i_{n} η_{n; η_{0}} = \frac{ω_{1; n} η_{n; η_{0}}}{ω_{2; n}} = \frac{T_{2; n} η_{n; η_{0}}}{T_{1; n}}$

whereby $η_{n; η_{0}}$ may vary from gear to gear according to the formulas listed in this table and $0 \leq η_{n; η_{0}} \leq 1$

[69] The torque ratio $μ_{n}$ is the ratio of
output torque $T_{2; n}$

to input torque $T_{1; n}$

minus efficiency losses

[70] utput torque $T_{2; n}$

[71] to input torque $T_{1; n}$

[72] us efficiency losses

[73] therefore corresponds (apart from the efficiency losses) to the reciprocal of the shaft speeds too
$μ_{n} = i_{n} η_{n; η_{0}} = \frac{ω_{1; n} η_{n; η_{0}}}{ω_{2; n}} = \frac{T_{2; n} η_{n; η_{0}}}{T_{1; n}}$

whereby $η_{n; η_{0}}$ may vary from gear to gear according to the formulas listed in this table and $0 \leq η_{n; η_{0}} \leq 1$

[74] $μ_{n} = i_{n} η_{n; η_{0}} = \frac{ω_{1; n} η_{n; η_{0}}}{ω_{2; n}} = \frac{T_{2; n} η_{n; η_{0}}}{T_{1; n}}$

[75] whereby $η_{n; η_{0}}$ may vary from gear to gear according to the formulas listed in this table and $0 \leq η_{n; η_{0}} \leq 1$

[Efficiency-33] 5.00 ^5.01 ^5.02 ^5.03 ^5.04 ^5.05 ^5.06 ^5.07 ^5.08 ^5.09 ^5.10 ^5.11 ^5.12 ^5.13 Efficiency
The efficiency $η_{n}$ is calculated
from the torque ratio

in relation to the gear ratio (transmission ratio)

$η_{n} = \frac{μ_{n}}{i_{n}}$

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, the stationary gear ratio $i_{0}$ 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 $η_{0}$ specified here are based on assumed efficiencies for the stationary ratio $i_{0}$
of $η_{0} = 0.9800$ (upper value)

and $η_{0} = 0.9700$ (lower value)

for both interventions together

The corresponding efficiency
for single-meshing gear pairs is ${η_{0}}^{\frac{1}{2}}$

at $0.980 0^{\frac{1}{2}} = 0.98995$ (upper value)

and $0.970 0^{\frac{1}{2}} = 0.98489$ (lower value)

[77] The efficiency $η_{n}$ is calculated
from the torque ratio

in relation to the gear ratio (transmission ratio)

$η_{n} = \frac{μ_{n}}{i_{n}}$

[78] rom the torque ratio

[79] relation to the gear ratio (transmission ratio)

[80] $η_{n} = \frac{μ_{n}}{i_{n}}$

[81] 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

[82] s in the range of 1 % to 1.5 %

[83] r pairs, which are used to reduce noise in passenger cars, are in the upper part of the loss range

[84] spur gear pairs, which are limited to commercial vehicles due to their poorer noise comfort, are in the lower part of the loss range

[85] tary gearsets, the stationary gear ratio $i_{0}$ is formed via the planetary gears and thus by two meshes

[86] r reasons of simplification, the efficiency for both meshes together is commonly specified there

[87] the efficiencies $η_{0}$ specified here are based on assumed efficiencies for the stationary ratio $i_{0}$
of $η_{0} = 0.9800$ (upper value)

and $η_{0} = 0.9700$ (lower value)

[88] $η_{0} = 0.9800$ (upper value)

[89] $η_{0} = 0.9700$ (lower value)

[90] r both interventions together

[91] The corresponding efficiency
for single-meshing gear pairs is ${η_{0}}^{\frac{1}{2}}$

at $0.980 0^{\frac{1}{2}} = 0.98995$ (upper value)

and $0.970 0^{\frac{1}{2}} = 0.98489$ (lower value)

[92] r single-meshing gear pairs is ${η_{0}}^{\frac{1}{2}}$

[93] t $0.980 0^{\frac{1}{2}} = 0.98995$ (upper value)

[94] $0.970 0^{\frac{1}{2}} = 0.98489$ (lower value)

[34] Layout
Input and output are on opposite sides

Planetary gearset 1 is on the input (turbine) side

Input (turbine) shafts are C₂ and, if actuated, R₃ and S₄

Output shaft is C₄

[96] Input and output are on opposite sides

[97] Planetary gearset 1 is on the input (turbine) side

[98] Input (turbine) shafts are C₂ and, if actuated, R₃ and S₄

[99] Output shaft is C₄

[35] Total Ratio Span (Total Gear/Transmission Ratio) Nominal
$\frac{ω_{2; n}}{ω_{2; 1}} = \frac{\frac{ω_{2; n}}{ω_{2; 1} ω_{2; n}}}{\frac{ω_{2; 1}}{ω_{2; 1} ω_{2; n}}} = \frac{\frac{1}{ω_{2; 1}}}{\frac{1}{ω_{2; n}}} = \frac{\frac{ω_{t}}{ω_{2; 1}}}{\frac{ω_{t}}{ω_{2; n}}} = \frac{i_{1}}{i_{n}}$

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

[101] $\frac{ω_{2; n}}{ω_{2; 1}} = \frac{\frac{ω_{2; n}}{ω_{2; 1} ω_{2; n}}}{\frac{ω_{2; 1}}{ω_{2; 1} ω_{2; n}}} = \frac{\frac{1}{ω_{2; 1}}}{\frac{1}{ω_{2; n}}} = \frac{\frac{ω_{t}}{ω_{2; 1}}}{\frac{ω_{t}}{ω_{2; n}}} = \frac{i_{1}}{i_{n}}$

[102] 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

[103] wnspeeding when driving outside the city limits

[104] rease the climbing ability
when driving over mountain passes or off-road

or when towing a trailer

[105] when driving over mountain passes or off-road

[106] r when towing a trailer

[effective-36] 8.0 ^8.1 ^8.2 ^8.3 ^8.4 ^8.5 ^8.6 Total Ratio Span (Total Gear Ratio/Total Transmission Ratio) Effective
$\frac{ω_{2; n}}{m a x (ω_{2; 1}; | ω_{2; R} |)} = \frac{m i n (i_{1}; | i_{R} |)}{i_{n}}$

The span is only effective to the extent that
the reverse gear ratio

matches that of 1st gear

see also Standard R:1
Digression
Reverse gear
is usually longer than 1st gear

the effective span is therefore of central importance for describing the suitability of a transmission

because in these cases, the nominal 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
the effective span has therefore not yet been able to establish itself
either in theory

or in practice.
End of digression

[108] $\frac{ω_{2; n}}{m a x (ω_{2; 1}; | ω_{2; R} |)} = \frac{m i n (i_{1}; | i_{R} |)}{i_{n}}$

[109] The span is only effective to the extent that
the reverse gear ratio

matches that of 1st gear

[110] the reverse gear ratio

[111] tches that of 1st gear

[112] see also Standard R:1

[113] s usually longer than 1st gear

[114] the effective span is therefore of central importance for describing the suitability of a transmission

[115] use in these cases, the nominal spread conveys a misleading picture

[116] which is only unproblematic for vehicles with high specific power

[117] Manufacturers naturally have no interest in specifying the effective span

[118] Users have not yet formulated the practical benefits that the effective span has for them

[119] The effective span has not yet played a role in research and teaching

[120] the effective span has therefore not yet been able to establish itself
either in theory

or in practice.

[121] ther in theory

[122] r in practice.

[37] Ratio Span's Center
$(i_{1} i_{n})^{\frac{1}{2}}$

The center indicates the speed level of the transmission

Together with the final drive ratio

it gives the shaft speed level of the vehicle

[124] $(i_{1} i_{n})^{\frac{1}{2}}$

[125] The center indicates the speed level of the transmission

[126] Together with the final drive ratio

[127] t gives the shaft speed level of the vehicle

[38] Average Gear Step
${(\frac{ω_{2; n}}{ω_{2; 1}})}^{\frac{1}{n - 1}} = {(\frac{i_{1}}{i_{n}})}^{\frac{1}{n - 1}}$

There are $n - 1$ gear steps between $n$ gears

with decreasing step width
the gears connect better to each other

shifting comfort increases

[129] ${(\frac{ω_{2; n}}{ω_{2; 1}})}^{\frac{1}{n - 1}} = {(\frac{i_{1}}{i_{n}})}^{\frac{1}{n - 1}}$

[130] There are $n - 1$ gear steps between $n$ gears

[131] with decreasing step width
the gears connect better to each other

shifting comfort increases

[132] the gears connect better to each other

[133] shifting comfort increases

[39] Sun 1: sun gear of gearset 1

[40] Ring 1: ring gear of gearset 1

[41] Sun 2: sun gear of gearset 2

[42] Ring 2: ring gear of gearset 2

[43] Sun 3: sun gear of gearset 3

[44] Ring 3: ring gear of gearset 3

[45] Sun 4: sun gear of gearset 4

[46] Ring 4: ring gear of gearset 4

[50:50-47] 19.00 ^19.01 ^19.02 ^19.03 ^19.04 ^19.05 ^19.06 ^19.07 ^19.08 ^19.09 ^19.10 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 3) is always larger

and the upper half of the gear steps (between the large gears; rounded up, here the last 4) 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)

[143] With steadily decreasing gear steps (yellow highlighted line Step)

[144] rticularly large step from 1st to 2nd gear
the lower half of the gear steps (between the small gears; rounded down, here the first 3) is always larger

and the upper half of the gear steps (between the large gears; rounded up, here the last 4) is always smaller

[145] the lower half of the gear steps (between the small gears; rounded down, here the first 3) is always larger

[146] the upper half of the gear steps (between the large gears; rounded up, here the last 4) is always smaller

[147] than the average gear step (cell highlighted yellow two rows above on the far right)

[148] wer half: smaller gear steps are a waste of possible ratios (red bold)

[149] upper half: larger gear steps are unsatisfactory (red bold)

[R:1-48] 20.00 ^20.01 ^20.02 ^20.03 ^20.04 ^20.05 ^20.06 ^20.07 ^20.08 ^20.09 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

[151] 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

[152] rment when maneuvering

[153] specially when towing a trailer

[154] torque converter can only partially compensate for this deficiency

[155] Plus 11.11 % minus 10 % compared to 1st gear is good

[156] Plus 25 % minus 20 % is acceptable (red)

[157] Above this is unsatisfactory (bold)

[158] see also Total Ratio Span (Total Gear/Transmission Ratio) Effective

[1:2-49] 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)

[160] With continuously decreasing gear steps (yellow marked line Step)

[161] the largest gear step is the one from 1st to 2nd gear, which
for a good speed connection and

a smooth gear shift

[162] r a good speed connection and

[163] smooth gear shift

[164] ust 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)

[165] A gear ratio of up to 1.6667 : 1 (5 : 3) is good

[166] Up to 1.7500 : 1 (7 : 4) is acceptable (red)

[167] Above is unsatisfactory (bold)

[LS-50] 22.0 ^22.1 ^22.2 ^22.3 From large to small gears (from right to left)

[Step-51] 23.00 ^23.01 ^23.02 ^23.03 ^23.04 ^23.05 ^23.06 ^23.07 ^23.08 ^23.09 ^23.10 ^23.11 ^23.12 ^23.13 ^23.14 ^23.15 ^23.16 ^23.17 ^23.18 ^23.19 ^23.20 ^23.21 ^23.22 ^23.23 ^23.24 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)

[170] 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

[171] increase: Δ Step (first green highlighted line Δ Step) is always greater than 1

[172] As progressive as possible: Δ Step is always greater than the previous step

[173] Not progressively increasing is acceptable (red)

[174] Not increasing is unsatisfactory (bold)

[Speed-52] 24.00 ^24.01 ^24.02 ^24.03 ^24.04 ^24.05 ^24.06 ^24.07 ^24.08 ^24.09 ^24.10 ^24.11 ^24.12 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)

[176] Shaft speed differences should
increase: Δ Shaft Speed (second line marked in green Δ (Shaft) Speed) is always greater than the previous one

[177] increase: Δ Shaft Speed (second line marked in green Δ (Shaft) Speed) is always greater than the previous one

[178] 1 difference smaller than the previous one is acceptable (red)

[179] 2 consecutive ones are a waste of possible ratios (bold)

[53] Model year 2015

[55] Model year 2016

[56] Permanently coupled elements
S₁ and R₂

C₁ and C₄

S₂ and S₃

C₃ and R₄

[183] S₁ and R₂

[184] C₁ and C₄

[185] S₂ and S₃

[186] C₃ and R₄

[57] Blocks S₂ and S₃

[58] Blocks R₃

[59] Couples C₂ and S₄ with the input (turbine)

[60] Couples R₁ with S₄

[61] Couples S₁ and R₂ with S₄

[Swap-62] 33.0 ^33.1 ^33.2 ^33.3 Adjusted formulas with gearset 1 and 3 swapped

[ordinary-63] 34.0 ^34.1 ^34.2 ^34.3 Ordinary Noted
For direct determination of the gear ratio

[194] For direct determination of the gear ratio

[elementary-64] 35.0 ^35.1 ^35.2 ^35.3 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

[196] Alternative representation for determining the transmission ratio

[197] Contains only operands
With simple fractions of both central gears of a planetary gearset

Or with the value 1

[198] With simple fractions of both central gears of a planetary gearset

[199] Or with the value 1

[200] As a basis
For reliable

And traceable

[201] For reliable

[202] And traceable

[203] Determination of specific torque and efficiency

[65] without generation designation

[66] First transmission on the market to use the dedicated 8-speed layout
gearset 1 and 3 not swapped

for comparison purposes only

[206] rset 1 and 3 not swapped

[207] r comparison purposes only

[NoSwap-68] 38.0 ^38.1 ^38.2 ^38.3 Original formulas
gearset 1 and 3 not swapped

for comparison purposes only

[209] rset 1 and 3 not swapped

[210] r comparison purposes only

[Standard-71] 1.0 ^1.1 Standard

[72] Z51

[75] Maximum Trailering Package

[Engine-76] 2.8 L diesel engine and 4.3 L gas engine only

[1] "US Patent 8,105,196 B2: Automatic Transmission Gear And Clutch Arrangement". US Patent Office. 31 January 2012. https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US8105196.pdf.

[dive-2] 2.0 ^2.1 ^2.2 Apakidze, Timur (11 March 2014). "Saturation Dive: ZF 8-Speed Automatic". TTAC: The Truth About Cars · Pt. 1. https://www.thetruthaboutcars.com/2014/03/saturation-dive-zf-8-speed-automatic/. and "loc. cit. · Pt. 2". 23 April 2014. https://www.thetruthaboutcars.com/2014/04/saturation-dive-zf-8-speed-automatic/.

[USA_Info_2018-3] 3.0 ^3.1 "USA Information Guide Model Year 2018". https://www.gmpowertrain.com/assets/docs/2018R_F3F_Information_Guide_031918.pdf.

[4] "Cadillac Introduces New 8-Speed Automatic on CT6". Cadillac Media USA. 20 March 2015. http://media.cadillac.com/media/us/en/cadillac/news.detail.html/content/Pages/news/us/en/2015/mar/0320-cadillac/0320-cadillac-8spd-trans.html.

[8L80RPO-5] 5.0 ^5.1 ^5.2 Regular production option

[8L45RPO-6] 6.0 ^6.1 "Gears Magazine - What's That Noise? GM 8-Speed Generation II" (in en-US). https://gearsmagazine.com/magazine/whats-that-noise-gm-8-speed-generation-ii/.

[7] "Gears Magazine - What's That Noise? GM 8-Speed Generation II" (in en-US). https://gearsmagazine.com/magazine/whats-that-noise-gm-8-speed-generation-ii/.

[9] "New 8-Speed Enables Quicker, More Efficient Corvette". General Motors. 20 August 2014. http://www.gm.com/article.content_pages_news_us_en_2014_aug_0820-8speed_0820-corvette-8-speed-lead.html.

[Repair_Cost-12] 9.0 ^9.1 "Transmission Repair Cost Guide". https://www.transmissionrepaircostguide.com/8l90/.

[16] "8L45 8-Speed GM OEM Transmission | GM Powered Solutions". https://poweredsolutions.gm.com/products/8L45-8-speed-transmission/.

[17] "8L90 8-Speed Automatic Transmission | GM Powered Solutions". https://poweredsolutions.gm.com/products/8l90-8-speed-transmission/.

[21] "Maximum driving enjoyment with maximum agility". ZF Friedrichshafen AG. http://www.zf.com/corporate/en/products/innovations/8hp_automatic_transmissions/more_driving_enjoyment/more_driving_enjoyment.html.

[54] "WIT · Whatever It Takes · Automatic Transmission Parts Catalog 2018+2019 Page 268". https://www.wittrans.com/catalog.

[70sun1+2-67] 14.0 ^14.1 8HP 70 Repair Manual · Picture 10106 p. 110 · Saarbruecken 2014 · https://avtgr.ru/upload/data/pdf/zf_instructions/8HP70.pdf

[69] "2015 Cadillac Escalade Updated with 8L 90 8-Speed Automatic and More Tech [Photo Gallery"]. 11 August 2014. http://www.autoevolution.com/news/2015-cadillac-escalade-updated-with-8l 90-8-speed-automatic-and-more-tech-photo-gallery-85117.html.

[70] "Chevrolet Confirms 2015 Corvette Stingray To Utilize 8L 90 Eight-Speed Gearbox". http://gmauthority.com/blog/2014/04/chevrolet-confirms-2015-corvette-stingray-to-utilize-8l90-eight-speed-gearbox/.

[73] "Supercharged 2015 Chevy Corvette Z06 takes the C7 beyond the ZR1 [w/video"]. http://www.autoblog.com/2014/01/13/2015-chevy-corvette-z06-detroit-2014/.

[Engine-74] 18.0 ^18.1 "GM confirms 2015 Silverado, Sierra to get 8-speed automatic". http://www.autoblog.com/2014/07/18/2015-chevy-silverado-gmc-sierra-8-speed-automatic/.

[uwu-77] 19.0 ^19.1 ^19.2 ^19.3 ^19.4 https://www.opn.ca6.uscourts.gov/opinions.pdf/25a0170p-06.pdf This article incorporates public domain text from this source.

[78] "Class Action Lawsuit Filed Over Alleged Shifting Defect in Certain General Motors Transmissions". 19 December 2018. https://www.classaction.org/news/class-action-lawsuit-filed-over-alleged-shifting-defect-in-certain-general-motors-transmissions.

[1]

[2]

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v t e Powertrain
Part of the Automobile series
Automotive engine	Diesel engine Electric Fuel cell Hybrid (Plug-in hybrid) Internal combustion engine Petrol engine Steam engine
Transmission	Automatic transmission Chain drive Clutch Constant-velocity joint Continuously variable transmission Coupling Differential Direct-shift gearbox Drive shaft Dual-clutch transmission Drive wheel Electrohydraulic manual transmission Electrorheological clutch Epicyclic gearing Fluid coupling Friction drive Gear stick Giubo Hotchkiss drive Limited-slip differential Locking differential Manual transmission Manumatic Parking pawl Park by wire Preselector gearbox Semi-automatic transmission Shift by wire Torque converter Transaxle Transmission control unit Universal joint
Wheels and tires	Wheel hub assembly Wheel Rim Alloy wheel Hubcap Tire Tubeless Radial Rain Snow Racing slick Off-road Run-flat Spare
Hybrid	Electric motor Hybrid vehicle drivetrain Electric generator Alternator
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Engineering:GM 8L transmission

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Combined Parallel and Serial Coupled Gearset Concept For More Gears And Improved Cost-Effectiveness

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Gearset Concept: Quality

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Engineering:GM 8L transmission

Key Data

Specifications

Combined Parallel and Serial Coupled Gearset Concept For More Gears And Improved Cost-Effectiveness

Main Objectives

Extent

Gearset Concept: Quality

Applications

Lawsuits and issues

See also

References

External links

Navigation

Wiki tools

Page tools

Other projects

Categories