GM 8L transmission

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]

8L 45 · 8L 90 · 8L 80
Overview
Manufacturer	General Motors
Production	2014–
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

The 8L 90 is the first 8-speed automatic transmission built by General Motors. It debut 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]

Gear Ratios^[a][8]

Model	Gear									Total Span	Span Center	Avg. Step	Compo- nents
	R	1	2	3	4	5	6	7	8
8L 90 · M5U · 2014 8L 80 · MFC+N8X · 2023	−3.818	4.560	2.971	2.075	1.688	1.270	1.000	0.845	0.652	6.999	1.724	1.320	4 Gearsets 2 Brakes 3 Clutches
8L 45 · M5N · 2015 8L 45 · N8R · 2023	−3.928	4.615	3.038	2.065	1.658	1.259	1.000	0.849	0.658	7.011	1.743	1.321
ZF 8HP 70 · 2008[b]	−3.297	4.696	3.130	2.104	1.667	1.285	1.000	0.839	0.667	7.043	1.769	1.322
Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage first transmission to use this 8-speed gearset concept. It has become the new benchmark for automatic transmissions

Specifications

Features

	8L 45 M5N + N8X[9]	8L 90 M5U 8L 80 MFC + N8X[10]
Input Capacity
Maximum engine power	308 bhp (230 kW)[a]	420 bhp (313 kW)[b]
Maximum gearbox torque	550 N⋅m (406 lb⋅ft)[a]	900 N⋅m (664 lb⋅ft)[b]
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)[a]	22,500 lb (10,210 kg)[b]
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)[a]	10.3 L (10.9 US qt)[b]
Weight	80 kg (176 lb)[a]	98.9 kg (218 lb)[b]
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[c] Toledo · Ohio · USA GMPT[c] Silao · Mexico
based on 2020 Chevrolet Colorado Z71 2WD Crew Cab · Short Bed General Motors estimate General Motors Powertrain

(Economic) Progress Gearset Concept

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).^[11]

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.

Innovation Strength Analysis

With Assessment	Output: Gear Ratios	Innovation Elasticity[a] Δ Output : Δ Input	Input: Main Components
			Total	Gearsets	Brakes	Clutches
8L Ref. Object	${\displaystyle n_{O1}}$ ${\displaystyle n_{O2}}$	Topic[a]	${\displaystyle n_{I}=n_{G}+}$ ${\displaystyle n_{B}+n_{C}}$	${\displaystyle n_{G1}}$ ${\displaystyle n_{G2}}$	${\displaystyle n_{B1}}$ ${\displaystyle n_{B2}}$	${\displaystyle n_{C1}}$ ${\displaystyle n_{C2}}$
Δ Number	${\displaystyle n_{O1}-n_{O2}}$		${\displaystyle n_{I1}-n_{I2}}$	${\displaystyle n_{G1}-n_{G2}}$	${\displaystyle n_{B1}-n_{B2}}$	${\displaystyle n_{C1}-n_{C2}}$
Relative Δ	Δ Output ${\displaystyle {\tfrac {n_{O1}-n_{O2}}{n_{O2}}}}$	${\displaystyle {\tfrac {n_{O1}-n_{O2}}{n_{O2}}}:{\tfrac {n_{I1}-n_{I2}}{n_{I2}}}}$ ${\displaystyle ={\tfrac {n_{O1}-n_{O2}}{n_{O2}}}}$·${\displaystyle {\tfrac {n_{I2}}{n_{I1}-n_{I2}}}}$	Δ Input ${\displaystyle {\tfrac {n_{I1}-n_{I2}}{n_{I2}}}}$	${\displaystyle {\tfrac {n_{G1}-n_{G2}}{n_{G2}}}}$	${\displaystyle {\tfrac {n_{B1}-n_{B2}}{n_{B2}}}}$	${\displaystyle {\tfrac {n_{C1}-n_{C2}}{n_{C2}}}}$
8L 6L[b]	8[c] 6[c]	Progress[a]	9 8	4 3[d]	2 2	3 3
Δ Number	2		1	1	0	0
Relative Δ	0.333 ${\displaystyle {\tfrac {1}{3}}}$	2.667[a] ${\displaystyle {\tfrac {1}{3}}:{\tfrac {1}{8}}={\tfrac {1}{3}}}$·${\displaystyle {\tfrac {8}{1}}={\tfrac {8}{3}}}$	0.125 ${\displaystyle {\tfrac {1}{8}}}$	0.333 ${\displaystyle {\tfrac {1}{3}}}$	0.000 ${\displaystyle {\tfrac {0}{2}}}$	0.000 ${\displaystyle {\tfrac {0}{3}}}$
8L 3-Speed[e]	8[c] 3[c]	Market Position[a]	9 7	4 2	2 3	3 2
Δ Number	5		2	2	-1	1
Relative Δ	1.667 ${\displaystyle {\tfrac {5}{3}}}$	5.833[a] ${\displaystyle {\tfrac {5}{3}}:{\tfrac {2}{7}}={\tfrac {5}{3}}}$·${\displaystyle {\tfrac {7}{2}}={\tfrac {35}{6}}}$	0.286 ${\displaystyle {\tfrac {2}{7}}}$	1.000 ${\displaystyle {\tfrac {1}{1}}}$	−0.333 ${\displaystyle {\tfrac {-1}{3}}}$	0.500 ${\displaystyle {\tfrac {1}{2}}}$
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 plus 1 reverse gear of which 2 gearsets are combined as a compound Ravigneaux gearset Reference Standard (Benchmark) 3-speed transmissions with torque converters have established the modern market for automatic transmissions and thus made it possible in the first place, as this design proved to be a particularly successful compromise between cost and performance It became the archetype and dominated the world market for around 3 decades, setting the standard for automatic transmissions. It was only when fuel consumption became the focus of interest that this design reached its limits, which is why it has now completely disappeared from the market What has remained is the orientation that it offers as a reference standard (point of reference, benchmark) for this market for determining progressiveness and thus the market position of all other, later designs All transmission variants consist of 7 main components Typical examples are Turbo-Hydramatic from GM Cruise-O-Matic from Ford TorqueFlite from Chrysler Detroit Gear from BorgWarner for Studebaker BW-35 from BorgWarner and as T35 from Aisin 3N 71 from Nissan/Jatco 3 HP from ZF Friedrichshafen W3A 040 and W3B 050 from Mercedes-Benz

Quality Gearset Concept

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

With Assessment			Planetary Gearset: Teeth[a][b]				Count	Total[c] Center[d]	Avg.[e]
Model Type	Version First Delivery		S1[f] R1[g]	S2[h] R2[i]	S3[j] R3[k]	S4[l] R4[m]	Brakes Clutches	Ratio Span	Gear Step[n]
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 ${\displaystyle {i_{8}}}$
Step[n]	${\displaystyle -{\tfrac {i_{R}}{i_{1}}}}$[o]	${\displaystyle {\tfrac {i_{1}}{i_{1}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{2}}}}$[p]	${\displaystyle {\tfrac {i_{2}}{i_{3}}}}$	${\displaystyle {\tfrac {i_{3}}{i_{4}}}}$	${\displaystyle {\tfrac {i_{4}}{i_{5}}}}$	${\displaystyle {\tfrac {i_{5}}{i_{6}}}}$	${\displaystyle {\tfrac {i_{6}}{i_{7}}}}$	${\displaystyle {\tfrac {i_{7}}{i_{8}}}}$
Δ Step[q][r]			${\displaystyle {\tfrac {i_{1}}{i_{2}}}:{\tfrac {i_{2}}{i_{3}}}}$	${\displaystyle {\tfrac {i_{2}}{i_{3}}}:{\tfrac {i_{3}}{i_{4}}}}$	${\displaystyle {\tfrac {i_{3}}{i_{4}}}:{\tfrac {i_{4}}{i_{5}}}}$	${\displaystyle {\tfrac {i_{4}}{i_{5}}}:{\tfrac {i_{5}}{i_{6}}}}$	${\displaystyle {\tfrac {i_{5}}{i_{6}}}:{\tfrac {i_{6}}{i_{7}}}}$	${\displaystyle {\tfrac {i_{6}}{i_{7}}}:{\tfrac {i_{7}}{i_{8}}}}$
Shaft Speed	${\displaystyle {\tfrac {i_{1}}{i_{R}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{1}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{2}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{3}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{4}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{5}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{6}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{7}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{8}}}}$
Δ Shaft Speed[s]	${\displaystyle 0-{\tfrac {i_{1}}{i_{R}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{1}}}-0}$	${\displaystyle {\tfrac {i_{1}}{i_{2}}}-{\tfrac {i_{1}}{i_{1}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{3}}}-{\tfrac {i_{1}}{i_{2}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{4}}}-{\tfrac {i_{1}}{i_{3}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{5}}}-{\tfrac {i_{1}}{i_{4}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{6}}}-{\tfrac {i_{1}}{i_{5}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{7}}}-{\tfrac {i_{1}}{i_{6}}}}$	${\displaystyle {\tfrac {i_{1}}{i_{8}}}-{\tfrac {i_{1}}{i_{7}}}}$
Specific Torque[t]	${\displaystyle {\tfrac {T_{2;R}}{T_{1;R}}}}$[u]	${\displaystyle {\tfrac {T_{2;1}}{T_{1;1}}}}$[u]	${\displaystyle {\tfrac {T_{2;2}}{T_{1;2}}}}$[u]	${\displaystyle {\tfrac {T_{2;3}}{T_{1;3}}}}$[u]	${\displaystyle {\tfrac {T_{2;4}}{T_{1;4}}}}$[u]	${\displaystyle {\tfrac {T_{2;5}}{T_{1;5}}}}$[u]	${\displaystyle {\tfrac {T_{2;6}}{T_{1;6}}}}$[u]	${\displaystyle {\tfrac {T_{2;7}}{T_{1;7}}}}$[u]	${\displaystyle {\tfrac {T_{2;8}}{T_{1;8}}}}$[u]
Efficiency ${\displaystyle \eta _{n}}$[t]	${\displaystyle {\tfrac {T_{2;R}}{T_{1;R}}}:{i_{R}}}$	${\displaystyle {\tfrac {T_{2;1}}{T_{1;1}}}:{i_{1}}}$	${\displaystyle {\tfrac {T_{2;2}}{T_{1;2}}}:{i_{2}}}$	${\displaystyle {\tfrac {T_{2;3}}{T_{1;3}}}:{i_{3}}}$	${\displaystyle {\tfrac {T_{2;4}}{T_{1;4}}}:{i_{4}}}$	${\displaystyle {\tfrac {T_{2;5}}{T_{1;5}}}:{i_{5}}}$	${\displaystyle {\tfrac {T_{2;6}}{T_{1;6}}}:{i_{6}}}$	${\displaystyle {\tfrac {T_{2;7}}{T_{1;7}}}:{i_{7}}}$	${\displaystyle {\tfrac {T_{2;8}}{T_{1;8}}}:{i_{8}}}$
8L 90-M5U 8L 80-MFC+N8X	900 N⋅m (664 lb⋅ft)[12] 2014[v] · 2023[5]		41[13] 79	46 86	37 73	25 89	2 3	6.9991 1.7236	1.3204[n]
Gear Ratio	−3.8176[o] ${\displaystyle -{\tfrac {43,043}{11,275}}}$	4.5600 ${\displaystyle {\tfrac {114}{25}}}$	2.9709[r] ${\displaystyle {\tfrac {817}{275}}}$	2.0751 ${\displaystyle {\tfrac {12,540}{6,043}}}$	1.6876[n][r][s] ${\displaystyle {\tfrac {4,121}{2,442}}}$	1.2700[r] ${\displaystyle {\tfrac {28,817,100}{22,690,429}}}$	1.0000 ${\displaystyle {\tfrac {1}{1}}}$	0.8455[r][s] ${\displaystyle {\tfrac {5,160}{6,103}}}$	0.6515 ${\displaystyle {\tfrac {43}{66}}}$
Step	0.8372[o]	1.0000	1.5349	1.4317	1.2297[n]	1.3288	1.2700	1.1828	1.2977
Δ Step[q]			1.0721[r]	1.1643	0.9254[r]	1.0463[r]	1.0738	0.9114[r]
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[s]	0.8884	0.9695	0.8333[s]	1.6057
Specific Torque[t]	–3.6149 –3.5155	4.48887 4.4532	2.9039 2.8704	2.0535 2.0255	1.6650 1.6385	1.2534 1.2366	1.0000	0.8411 0.8409	0.6469 0.6446
Efficiency ${\displaystyle \eta _{n}}$[t]	0.9469 0.9209	0.9844 0.9766	0.9774 0.9662	0.9896 0.9761	0.9866 0.9709	0.9869 0.9737	1.0000	0.9948 0.9945	0.9929 0.9893
8L 45 M5N	550 N⋅m (406 lb⋅ft) 2015[w] · 2023[6]		41 79	41 79	41 79	26 94	2 3	7.0107 1.7431	1.3208[n]
Gear Ratio	−3.9278[o] ${\displaystyle -{\tfrac {4,187}{1,066}}}$	4.6154 ${\displaystyle {\tfrac {60}{13}}}$	3.0385[r] ${\displaystyle {\tfrac {79}{26}}}$	2.0648 ${\displaystyle {\tfrac {7,200}{3,487}}}$	1.6583[n][r][s] ${\displaystyle {\tfrac {199}{120}}}$	1.2587[r] ${\displaystyle {\tfrac {740,760}{588,527}}}$	1.0000 ${\displaystyle {\tfrac {1}{1}}}$	0.8494[r][s] ${\displaystyle {\tfrac {9,480}{11,161}}}$	0.6583 ${\displaystyle {\tfrac {79}{120}}}$
Step	0.8510[o]	1.0000	1.5190	1.4715	1.2451[n]	1.3175	1.2587	1.1773	1.2902
Δ Step[q]			1.0322[r]	1.1819	0.9450[r]	1.0468[r]	1.0691	0.9125[r]
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[s]	0.8837	0.9485	0.8184[s]	1.5769
Specific Torque[t]	–3.7202 –3.6185	4.5431 4.5069	2.9701 2.9360	2.0435 2.0328	1.6366 1.6258	1.2425 1.2344	1.0000	0.8451 0.8428	0.6538 0.6514
Efficiency ${\displaystyle \eta _{n}}$[t]	0.9472 0.9213	0.9843 0.9765	0.9775 0.9663	0.9897 0.9845	0.9869 0.9804	0.9872 0.9807	1.0000	0.9949 0.9923	0.9931 0.9895
Geometric Ratios
Ratio[x] R & Even Ordinary[y] Elementary Noted[z]	${\displaystyle i_{R}={\tfrac {R_{2}(S_{1}S_{4}-R_{1}R_{4})}{S_{1}S_{4}(S_{2}+R_{2})}}}$		${\displaystyle i_{2}={\tfrac {R_{2}(S_{4}+R_{4})}{(S_{2}+R_{2})S_{4}}}}$		${\displaystyle i_{4}=1+{\tfrac {S_{2}R_{3}}{S_{3}(S_{2}+R_{2})}}}$		${\displaystyle i_{6}={\tfrac {1}{1}}}$	${\displaystyle i_{8}={\tfrac {R_{2}}{S_{2}+R_{2}}}}$
	${\displaystyle i_{R}={\tfrac {1-{\tfrac {R_{1}R_{4}}{S_{1}S_{4}}}}{1+{\tfrac {S_{2}}{R_{2}}}}}}$		${\displaystyle i_{2}={\tfrac {1+{\tfrac {R_{4}}{S_{4}}}}{1+{\tfrac {S_{2}}{R_{2}}}}}}$		${\displaystyle i_{4}=1+{\tfrac {\tfrac {R_{3}}{S_{3}}}{1+{\tfrac {R_{2}}{S_{2}}}}}}$			${\displaystyle i_{8}={\tfrac {1}{1+{\tfrac {S_{2}}{R_{2}}}}}}$
Ratio[x] Odd Ordinary[y] Elementary Noted[z]	${\displaystyle i_{1}={\tfrac {S_{4}+R_{4}}{S_{4}}}}$		${\displaystyle {\tfrac {(S_{3}+R_{3})(S_{4}+R_{4})}{S_{4}R_{3}+S_{3}(S_{4}+R_{4})}}}$		${\displaystyle {\tfrac {S_{3}R_{2}R_{4}(S_{1}+R_{1})+S_{2}S_{1}(S_{3}+R_{3})(S_{4}+R_{4})}{S_{3}R_{4}(S_{1}(S_{2}+R_{2})+R_{1}R_{2})+S_{1}S_{2}S_{4}(S_{3}+R_{3})}}}$			${\displaystyle {\tfrac {R_{2}(S_{1}+R_{1})}{R_{2}(S_{1}+R_{1})+S_{1}S_{2}}}}$
	${\displaystyle i_{1}=1+{\tfrac {R_{4}}{S_{4}}}}$		${\displaystyle i_{3}={\tfrac {1}{{\tfrac {1}{1+{\tfrac {R_{3}}{S_{3}}}}}+{\tfrac {1}{(1+{\tfrac {S_{3}}{R_{3}}})(1+{\tfrac {R_{4}}{S_{4}}})}}}}}$				${\displaystyle i_{7}={\tfrac {1}{1+{\tfrac {\tfrac {S_{2}}{R_{2}}}{1+{\tfrac {R_{1}}{S_{1}}}}}}}}$
	${\displaystyle i_{5}={\tfrac {1}{{\tfrac {1}{{\tfrac {(1+{\tfrac {R_{3}}{S_{3}}})(1+{\tfrac {S_{4}}{R_{4}}})}{1+{\tfrac {R_{2}}{S_{2}}}(1+{\tfrac {R_{1}}{S_{1}}})}}+{\tfrac {1}{{\tfrac {1}{1+{\tfrac {S_{1}}{R_{1}}}}}+{\tfrac {1+{\tfrac {S_{2}}{R_{2}}}}{1+{\tfrac {R_{1}}{S_{1}}}}}}}}}+{\tfrac {1}{1+{\tfrac {R_{4}}{S_{4}}}+{\tfrac {{\tfrac {R_{2}R_{4}}{S_{2}S_{4}}}(1+{\tfrac {R_{1}}{S_{1}}})}{1+{\tfrac {R_{3}}{S_{3}}}}}}}}}}$
Kinetic Ratios
Specific Torque[t] R & Even	${\displaystyle {\tfrac {T_{2;R}}{T_{1;R}}}={\tfrac {1-{\tfrac {R_{1}R_{4}}{S_{1}S_{4}}}\eta _{0}^{2}}{1+{\tfrac {S_{2}}{R_{2}}}{\tfrac {1}{\eta _{0}}}}}}$		${\displaystyle {\tfrac {T_{2;2}}{T_{1;2}}}={\tfrac {1+{\tfrac {R_{4}}{S_{4}}}\eta _{0}}{1+{\tfrac {S_{2}}{R_{2}}}{\tfrac {1}{\eta _{0}}}}}}$		${\displaystyle {\tfrac {T_{2;4}}{T_{1;4}}}=1+{\tfrac {{\tfrac {R_{3}}{S_{3}}}\eta _{0}}{1+{\tfrac {R_{2}}{S_{2}}}{\tfrac {1}{\eta _{0}}}}}}$		${\displaystyle {\tfrac {T_{2;6}}{T_{1;6}}}={\tfrac {1}{1}}}$	${\displaystyle {\tfrac {T_{2;8}}{T_{1;8}}}={\tfrac {1}{1+{\tfrac {S_{2}}{R_{2}}}{\tfrac {1}{\eta _{0}}}}}}$
Specific Torque[t] Odd	${\displaystyle {\tfrac {T_{2;1}}{T_{1;1}}}=1+{\tfrac {R_{4}}{S_{4}}}{\eta _{0}}}$		${\displaystyle {\tfrac {T_{2;3}}{T_{1;3}}}={\tfrac {1}{{\tfrac {1}{1+{\tfrac {R_{3}}{S_{3}}}\eta _{0}^{\tfrac {1}{2}}}}+{\tfrac {1}{(1+{\tfrac {S_{3}}{R_{3}}}\eta _{0}^{\tfrac {1}{2}})(1+{\tfrac {R_{4}}{S_{4}}}\eta _{0})}}}}}$				${\displaystyle {\tfrac {T_{2;7}}{T_{1;7}}}={\tfrac {1}{1+{\tfrac {{\tfrac {S_{2}}{R_{2}}}{\tfrac {1}{\eta _{0}}}}{1+{\tfrac {R_{1}}{S_{1}}}\eta _{0}}}}}}$
	${\displaystyle {\tfrac {T_{2;5}}{T_{1;5}}}={\tfrac {1}{{\tfrac {1}{{\tfrac {(1+{\tfrac {R_{3}}{S_{3}}}\eta _{0}^{\tfrac {1}{2}})(1+{\tfrac {S_{4}}{R_{4}}}\eta _{0}^{\tfrac {1}{2}})}{1+{\tfrac {R_{2}}{S_{2}}}{\tfrac {1}{\eta _{0}^{\tfrac {1}{2}}}}(1+{\tfrac {R_{1}}{S_{1}}}{\tfrac {1}{\eta _{0}^{\tfrac {1}{4}}}})}}+{\tfrac {1}{{\tfrac {1}{1+{\tfrac {S_{1}}{R_{1}}}\eta _{0}^{\tfrac {1}{4}}}}+{\tfrac {1+{\tfrac {S_{2}}{R_{2}}}{\tfrac {1}{\eta _{0}^{\tfrac {1}{2}}}}}{1+{\tfrac {R_{1}}{S_{1}}}\eta _{0}^{\tfrac {1}{4}}}}}}}}+{\tfrac {1}{1+{\tfrac {R_{4}}{S_{4}}}\eta _{0}^{\tfrac {1}{2}}+{\tfrac {{\tfrac {R_{2}R_{4}}{S_{2}S_{4}}}\eta _{0}^{2}(1+{\tfrac {R_{1}}{S_{1}}}\eta _{0}^{\tfrac {1}{4}})}{1+{\tfrac {R_{3}}{S_{3}}}{\tfrac {1}{\eta _{0}^{\tfrac {1}{2}}}}}}}}}}}$
Actuated Shift Elements[aa]
Brake A[ab]	❶	❶	❶					❶	❶
Brake B[ac]	❶	❶	❶	❶	❶	❶
Clutch C[ad]		❶		❶		❶	❶	❶
Clutch D[ae]	❶				❶	❶	❶	❶	❶
Clutch E[af]			❶	❶	❶		❶		❶
8HP70 [ag][ah]	700 N⋅m (516 lb⋅ft) 2008		48[14] 96	48[14] 96	69[2] 111	23[2] 85	2 3	7.0435 1.7693	1.3216[n]
Gear Ratio	−3.2968[o] ${\displaystyle -{\tfrac {1,744}{529}}}$	4.6957 ${\displaystyle {\tfrac {108}{23}}}$	3.1304[r] ${\displaystyle {\tfrac {72}{23}}}$	2.1039 ${\displaystyle {\tfrac {162}{77}}}$	1.6667[n][r][s] ${\displaystyle {\tfrac {5}{3}}}$	1.2845[r] ${\displaystyle {\tfrac {8,826}{6,871}}}$	1.0000 ${\displaystyle {\tfrac {1}{1}}}$	0.8392[r][s] ${\displaystyle {\tfrac {120}{143}}}$	0.6667 ${\displaystyle {\tfrac {2}{3}}}$
Step	0.7021[o]	1.0000	1.5000	1.4879	1.2623[n]	1.2975	1.2845	1.1917	1.2587
Δ Step[q]			1.0081[r]	1.1787	0.9729[r]	1.0101[r]	1.0779	0.9467[r]
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[s]	0.8382	1.0401	0.9000[s]	1.4478
Specific Torque[t]	–3.1186 –3.0313	4.6217 4.5848	3.0603 3.0253	2.0820 2.0709	1.6446 1.6336	1.2676 1.2591	1.0000	0.8347 0.8324	0.6622 0.6599
Efficiency ${\displaystyle \eta _{n}}$[t]	0.9460 0.9195	0.9843 0.9764	0.9776 0.9664	0.9896 0.9843	0.9867 0.9802	0.9868 0.9802	1.0000	0.9947 0.9920	0.9932 0.9898
Ratio[ai] R & Even	${\displaystyle i_{R}={\tfrac {R_{2}(S_{3}S_{4}-R_{3}R_{4})}{S_{3}S_{4}(S_{2}+R_{2})}}}$		${\displaystyle i_{2}={\tfrac {R_{2}(S_{4}+R_{4})}{(S_{2}+R_{2})S_{4}}}}$		${\displaystyle i_{4}=1+{\tfrac {S_{2}R_{1}}{S_{1}(S_{2}+R_{2})}}}$		${\displaystyle i_{6}={\tfrac {1}{1}}}$	${\displaystyle i_{8}={\tfrac {R_{2}}{S_{2}+R_{2}}}}$
Ratio[ai] Odd	${\displaystyle i_{1}={\tfrac {S_{4}+R_{4}}{S_{4}}}}$		${\displaystyle {\tfrac {(S_{1}+R_{1})(S_{4}+R_{4})}{S_{4}R_{1}+S_{1}(S_{4}+R_{4})}}}$		${\displaystyle {\tfrac {S_{1}R_{2}R_{4}(S_{3}+R_{3})+S_{2}S_{3}(S_{1}+R_{1})(S_{4}+R_{4})}{S_{1}R_{4}(S_{3}(S_{2}+R_{2})+R_{2}R_{3})+S_{2}S_{3}S_{4}(S_{1}+R_{1})}}}$			${\displaystyle {\tfrac {R_{2}(S_{3}+R_{3})}{R_{2}(S_{3}+R_{3})+S_{2}S_{3}}}}$
All 8L-transmissions are based on a dedicated 8-speed layout, first realized in the ZF 8HP 70 gearbox Layout Input and output are on opposite sides Planetary gearset 1 is on the input (turbine) side Input shafts are C2 and, if actuated, R3 and S4 Output shaft is C4 (planetary gear carrier of gearset 4) Total Ratio Span (Total Ratio Spread · Total Gear Ratio) ${\displaystyle {\tfrac {i_{1}}{i_{n}}}}$ 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 Ratio Span's Center ${\displaystyle (i_{1}i_{n})^{\tfrac {1}{2}}}$ 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 ${\displaystyle ({\tfrac {i_{1}}{i_{n}}})^{\tfrac {1}{n-1}}}$ With decreasing step width the gears connect better to each other shifting comfort increases Sun 1: sun gear of gearset 1 Ring 1: ring gear of gearset 1 Sun 2: sun gear of gearset 2 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 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) 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) 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) From large to small gears (from right to left) 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) 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) Specific Torque Ratio And Efficiency The specific torque is the Ratio of output torque ${\displaystyle T_{2;Gear}}$ to input torque ${\displaystyle T_{1;Gear}}$ with ${\displaystyle n=gear}$ The efficiency is calculated from the specific torque in relation to the transmission ratio Power loss for single meshing gears is in the range of 1 % to 1.5 % helical gear pairs, which are used to reduce noise in passenger cars, are in the upper part of the loss range spur gear pairs, which are limited to commercial vehicles due to their poorer noise comfort, are in the lower part of the loss range Corridor for specific torque and efficiency in planetary gearsets, the stationary gear ratio ${\displaystyle i_{0}}$ is formed via the planetary gears and thus by two meshes for reasons of simplification, the efficiency for both meshes together is commonly specified there the efficiencies ${\displaystyle \eta _{0}}$ specified here are based on assumed efficiencies for the stationary ratio ${\displaystyle i_{0}}$ of ${\displaystyle \eta _{0}=0.9800}$ (upper value) and ${\displaystyle \eta _{0}=0.9700}$ (lower value) for both interventions together The corresponding efficiency for single-meshing gear pairs is ${\displaystyle \eta _{0}^{\tfrac {1}{2}}}$ at ${\displaystyle 0.9800^{\tfrac {1}{2}}=0.98995}$ (upper value) and ${\displaystyle 0.9700^{\tfrac {1}{2}}=0.98489}$ (lower value) Model year 2015 Model year 2016 Adjusted formulas with gearset 1 and 3 swapped Ordinary Noted For direct determination of the ratio 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 Permanently coupled elements S1 and R2 C1 (carrier 1) and C4 (carrier 4) S2 and S3 C3 (carrier 3) and R4 Blocks S2 and S3 Blocks R3 Couples C2 and S4 with the turbine Couples R1 with S4 Couples S1 and R2 with S4 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 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[a] or 2.73[b]
	2015–2019	Corvette (C7) Z06[17]	2.41
	2019	Corvette (C7) ZR1	2.73
	2015–present	Silverado[18]	3.23[a] or 3.42[c]
	2015–present	Colorado	3.42
	2016–2018	Camaro SS	2.77
	2017–present	Express[d]
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
	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
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]

See also

• List of GM transmissions