GM 8L transmission

Template:Use American English Template:Infobox automobile

The 8L is the first 8-speed automatic transmission built by General Motors. All 8L transmissions are based on the same globally patented gearset concept as the ZF 8HP from 2008 and, like this, are designed for longitudinal engine installation and features a hydraulic (Hydramatic) design. While fully retaining the same gearset logic, they differ only in the patented^[1] arrangement of the components, with planetary gearsets 1 and 3 swapped.^[2]

History

2014: 8L 90 M5U

The 8L 90 was introduced in 2014 and is designed to be 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).

2015: 8L 45 M5N

The 8L 45 is the smaller variant and was launched in 2015 in the 2016 Cadillac CT6. It is always attached to the front-located engine^[3] with a standard bell housing. It shares much with the 8L 90 transmission.^[4] Estimated weight savings over the heavier-duty 8L 90 is Template:Convert.

2023: 8L 80 MFC/N8X and 8L 45 N8R

The 8L 80 is an updated version with new RPO^[5] codes MFC and N8X and was introduced on the 2023 model years of the Chevrolet Colorado and GMC Canyon.^[6] A second generation of the 8L 45 was introduced in 2023 model years with a new RPO^[5] code N8R.^[6]

Key data

Gear ratiosTemplate:Efn^[7]
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 GearTemplate:Efn	Gears Count	Cou- pling	Gear- sets	Maximum Input Torque

8L 90 · 8L 80	M5U · MFC+N8X	2014 · 2023	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	4 Gearsets 2 Brakes 3 Clutches	Template:Round	8Template:Efn	LTemplate:Efn		Template:Convert^[8]
8L 45	M5N · N8R	2015 · 2023	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round				LTemplate:Efn		Template:Convert

ZF 8HP 70Template:Efn		2008	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round	Template:Round				HTemplate:Efn	PTemplate:Efn	Template:Convert – Template:Convert

Template:Notelist

Specifications

Features
	8L 45 M5N + N8R^[9]	8L 90 M5U 8L 80 MFC + N8X^[10]

Input capacity
Maximum engine power	Template:Convert Template:Efn	Template:Convert Template:Efn
Maximum gearbox torque	Template:Convert Template:Efn	Template:Convert Template:Efn
Maximum shaft speed	7,500/min	6,000/min
Vehicle
Maximum validated weight Gross vehicle weight · GVW	—	—
Maximum validated weight Gross curb vehicle weight · GCVW	Template:Convert Template:Efn	Template:Convert Template:Efn
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	Template:Convert	Template:Convert
Fluid type	DEXRON high performance ATF
Fluid capacity	Template:Convert Template:Efn	Template:Convert Template:Efn
Weight	Template:Convert Template:Efn	Template:Convert Template:Efn
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	GMPTTemplate:Efn Toledo · Ohio · USA GMPTTemplate:Efn Silao · Mexico

Template:Notelist

Planetary gearset concept

Improved fuel economy

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), which is a decisive factor in improving energy efficiency and thus reducing fuel consumption. In addition, the lower engine speed level improves the noise-vibration-harshness comfort and the exterior noise is reduced. Due to changes in internal design, the shift times are reduced to 0.2 seconds.

Reduced manufacturing complexity

In order to avoid a further increase in manufacturing complexity while expanding the number of gear ratios, ZF and consequently GM switched from the conventional design method—in which the planetary gearset concept was limited to a purely serial or in-line power flow—to a more modern design method that utilizes a planetary gearset concept with combined parallel and serial power flow. 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 8HP has become the new reference standard (benchmark) for automatic transmissions.

Planetary gearset concept: manufacturing complexityTemplate:Efn
With Assessment	Output: Gear Ratios	Innovation Elasticity Template:Efn Δ Output : Δ Input	Input: Main Components
With Assessment	Output: Gear Ratios	Innovation Elasticity Template:Efn Δ Output : Δ Input	Total	Gearsets	Brakes	Clutches

8L Ref. Object	$n_{O 1}$ $n_{O 2}$	TopicTemplate:Efn	$n_{I} = n_{G} +$ $n_{B} + n_{C}$	$n_{G 1}$ $n_{G 2}$	$n_{B 1}$ $n_{B 2}$	$n_{C 1}$ $n_{C 2}$
Δ Number	$n_{O 1} - n_{O 2}$	TopicTemplate:Efn	$n_{I 1} - n_{I 2}$	$n_{G 1} - n_{G 2}$	$n_{B 1} - n_{B 2}$	$n_{C 1} - n_{C 2}$
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 Template:Efn	8Template:Efn 6Template:Efn	ProgressTemplate:Efn	9 8	4 3Template:Efn	2 2	3 3
Δ Number	2	ProgressTemplate:Efn	1	1	0	0
Relative Δ	Template:Round $\frac{1}{3}$	Template:RoundTemplate:Efn $\frac{1}{3} : \frac{1}{8} = \frac{1}{3}$ · $\frac{8}{1} = \frac{8}{3}$	Template:Round $\frac{1}{8}$	Template:Round $\frac{1}{3}$	Template:Round $\frac{0}{2}$	Template:Round $\frac{0}{3}$

8L ZF 8HP Template:Efn	8Template:Efn 8Template:Efn	Current Market PositionTemplate:Efn	9 9	4 4	2 2	3 3
Δ Number	0	Current Market PositionTemplate:Efn	0	0	0	0
Relative Δ	Template:Round $\frac{0}{8}$	Template:RoundTemplate:Efn $\frac{0}{8} : \frac{0}{9} = \frac{0}{8}$ · $\frac{9}{0} = \frac{0}{0}$	Template:Round $\frac{0}{9}$	Template:Round $\frac{0}{4}$	Template:Round $\frac{0}{2}$	Template:Round $\frac{0}{3}$

8L 3-SpeedTemplate:Efn	8Template:Efn 3Template:Efn	Historical Market PositionTemplate:Efn	9 7	4 2	2 3	3 2
Δ Number	5	Historical Market PositionTemplate:Efn	2	2	-1	1
Relative Δ	Template:Round $\frac{5}{3}$	Template:RoundTemplate:Efn $\frac{5}{3} : \frac{2}{7} = \frac{5}{3}$ · $\frac{7}{2} = \frac{35}{6}$	Template:Round $\frac{2}{7}$	Template:Round $\frac{1}{1}$	Template:Round $\frac{- 1}{3}$	Template:Round $\frac{1}{2}$

Template:Notelist

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.

Additionally, 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 brake B and releasing clutch D).^[11]

Planetary gearset concept: gear ratio qualityTemplate:Efn Template:Efn
In-Depth AnalysisTemplate:Efn With Assessment And Torque RatioTemplate:Efn And Efficiency CalculationTemplate:Efn			Planetary Gearset: TeethTemplate:Efn				Count	Nomi- nalTemplate:Efn Effec- tiveTemplate:Efn	Cen- terTemplate:Efn
			Planetary Gearset: TeethTemplate:Efn				Count	Nomi- nalTemplate:Efn Effec- tiveTemplate:Efn	Avg.Template:Efn

Model Type	Version First Delivery		S₁Template:Efn R₁Template:Efn	S₂Template:Efn R₂Template:Efn	S₃Template:Efn R₃Template:Efn	S₄Template:Efn R₄Template:Efn	Brakes Clutches	Ratio Span	Gear StepTemplate:Efn
Gear	R	1	2	3	4	5	6	7	8
Gear RatioTemplate:Efn	$i_{R}$ Template:Efn	$i_{1}$ Template:Efn	$i_{2}$ Template:Efn	$i_{3}$ Template:Efn	$i_{4}$ Template:Efn	$i_{5}$ Template:Efn	$i_{6}$ Template:Efn	$i_{7}$ Template:Efn	$i_{8}$ Template:Efn
StepTemplate:Efn	$- \frac{i_{R}}{i_{1}}$ Template:Efn	$\frac{i_{1}}{i_{1}}$	$\frac{i_{1}}{i_{2}}$ Template:Efn	$\frac{i_{2}}{i_{3}}$	$\frac{i_{3}}{i_{4}}$	$\frac{i_{4}}{i_{5}}$	$\frac{i_{5}}{i_{6}}$	$\frac{i_{6}}{i_{7}}$	$\frac{i_{7}}{i_{8}}$
Δ StepTemplate:Efn Template:Efn			$\frac{i_{1}}{i_{2}} : \frac{i_{2}}{i_{3}}$	$\frac{i_{2}}{i_{3}} : \frac{i_{3}}{i_{4}}$	$\frac{i_{3}}{i_{4}} : \frac{i_{4}}{i_{5}}$	$\frac{i_{4}}{i_{5}} : \frac{i_{5}}{i_{6}}$	$\frac{i_{5}}{i_{6}} : \frac{i_{6}}{i_{7}}$	$\frac{i_{6}}{i_{7}} : \frac{i_{7}}{i_{8}}$
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 SpeedTemplate:Efn	$0 - \frac{i_{1}}{i_{R}}$	$\frac{i_{1}}{i_{1}} - 0$	$\frac{i_{1}}{i_{2}} - \frac{i_{1}}{i_{1}}$	$\frac{i_{1}}{i_{3}} - \frac{i_{1}}{i_{2}}$	$\frac{i_{1}}{i_{4}} - \frac{i_{1}}{i_{3}}$	$\frac{i_{1}}{i_{5}} - \frac{i_{1}}{i_{4}}$	$\frac{i_{1}}{i_{6}} - \frac{i_{1}}{i_{5}}$	$\frac{i_{1}}{i_{7}} - \frac{i_{1}}{i_{6}}$	$\frac{i_{1}}{i_{8}} - \frac{i_{1}}{i_{7}}$
Torque RatioTemplate:Efn	$μ_{R}$ Template:Efn	$μ_{1}$ Template:Efn	$μ_{2}$ Template:Efn	$μ_{3}$ Template:Efn	$μ_{4}$ Template:Efn	$μ_{5}$ Template:Efn	$μ_{6}$ Template:Efn	$μ_{7}$ Template:Efn	$μ_{8}$ Template:Efn
Efficiency $η_{n}$ Template:Efn	$\frac{μ_{R}}{i_{R}}$ Template:Efn	$\frac{μ_{1}}{i_{1}}$ Template:Efn	$\frac{μ_{2}}{i_{2}}$ Template:Efn	$\frac{μ_{3}}{i_{3}}$ Template:Efn	$\frac{μ_{4}}{i_{4}}$ Template:Efn	$\frac{μ_{5}}{i_{5}}$ Template:Efn	$\frac{μ_{6}}{i_{6}}$ Template:Efn	$\frac{μ_{7}}{i_{7}}$ Template:Efn	$\frac{μ_{8}}{i_{8}}$ Template:Efn

8L 90-M5U 8L 80-MFC 8L 80-N8X	Template:Convert^[8] 2014Template:Efn · 2023^[5]		41^[12] 79	46 86	37 73	25 89	2 3	Template:Round Template:Font color	Template:Round
8L 90-M5U 8L 80-MFC 8L 80-N8X	Template:Convert^[8] 2014Template:Efn · 2023^[5]		41^[12] 79	46 86	37 73	25 89	2 3	Template:Round Template:Font color	Template:Font color Template:Efn
Gear	R	1	2	3	4	5	6	7	8
Gear RatioTemplate:Efn	Template:Font color	Template:Round $\frac{114}{25}$	Template:Font color	Template:Round $\frac{12, 540}{6, 043}$	Template:Font color	Template:Font color	Template:Round $\frac{1}{1}$	Template:Font color	Template:Round $\frac{43}{66}$
Step	Template:Font color Template:Efn	1.0000	Template:Font color	1.4317	Template:Font color Template:Efn	Template:Font color	1.2700	Template:Font color	1.2977
Δ StepTemplate:Efn			Template:Font color Template:Efn	1.1643	Template:Font color Template:Efn	Template:Font color Template:Efn	1.0738	Template:Font color Template:Efn
Speed	Template:Font color	1.0000	1.5349	2.1975	Template:Font color	3.5905	4.56	Template:Font color	6.9991
Δ Speed	Template:Font color	1.0000	0.5349	0.6626	Template:Font color Template:Efn	0.8884	0.9695	Template:Font color Template:Efn	1.6057
Torque RatioTemplate:Efn	–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 $η_{n}$ Template:Efn	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	Template:Convert 2015Template:Efn · 2023^[6]		41 79	41 79	41 79	26 94	2 3	Template:Round Template:Font color	Template:Round
8L 45 M5N	Template:Convert 2015Template:Efn · 2023^[6]		41 79	41 79	41 79	26 94	2 3	Template:Round Template:Font color	Template:Font color Template:Efn
Gear	R	1	2	3	4	5	6	7	8
Gear RatioTemplate:Efn	Template:Font color	Template:Round $\frac{60}{13}$	Template:Font color	Template:Round $\frac{7, 200}{3, 487}$	Template:Font color	Template:Font color	Template:Round $\frac{1}{1}$	Template:Font color	Template:Round $\frac{79}{120}$
Step	Template:Font color Template:Efn	1.0000	Template:Font color	1.4715	Template:Font color Template:Efn	Template:Font color	1.2587	Template:Font color	1.2902
Δ StepTemplate:Efn			Template:Font color Template:Efn	1.1819	Template:Font color Template:Efn	Template:Font color Template:Efn	1.0691	Template:Font color Template:Efn
Speed	Template:Font color	1.0000	1.5190	2.2353	Template:Font color	3.6669	4.6154	Template:Font color	7.0107
Δ Speed	Template:Font color	1.0000	0.5190	0.7163	Template:Font color Template:Efn	0.8837	0.9485	Template:Font color Template:Efn	1.5769
Torque RatioTemplate:Efn	–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 $η_{n}$ Template:Efn	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 elementsTemplate:Efn
Brake ATemplate:Efn	❶	❶	❶					❶	❶
Brake BTemplate:Efn	❶	❶	❶	❶	❶	❶
Clutch CTemplate:Efn		❶		❶		❶	❶	❶
Clutch DTemplate:Efn	❶				❶	❶	❶	❶	❶
Clutch ETemplate:Efn			❶	❶	❶		❶		❶
Geometric ratios: speed conversion
Gear RatioTemplate:Efn Template:Efn R & 1 & 2 OrdinaryTemplate:Efn Elementary NotedTemplate:Efn	$i_{R} = \frac{R_{2} (S_{1} S_{4} - R_{1} R_{4})}{S_{1} S_{4} (S_{2} + R_{2})}$			$i_{1} = \frac{S_{4} + R_{4}}{S_{4}}$			$i_{2} = \frac{R_{2} (S_{4} + R_{4})}{(S_{2} + R_{2}) S_{4}}$
	$i_{R} = \frac{1 - \frac{R_{1} R_{4}}{S_{1} S_{4}}}{1 + \frac{S_{2}}{R_{2}}}$			$i_{1} = 1 + \frac{R_{4}}{S_{4}}$			$i_{2} = \frac{1 + \frac{R_{4}}{S_{4}}}{1 + \frac{S_{2}}{R_{2}}}$

Gear RatioTemplate:Efn Template:Efn 3 & 4 OrdinaryTemplate:Efn Elementary NotedTemplate:Efn	$i_{3} = \frac{(S_{3} + R_{3}) (S_{4} + R_{4})}{S_{4} R_{3} + S_{3} (S_{4} + R_{4})}$					$i_{4} = 1 + \frac{S_{2} R_{3}}{S_{3} (S_{2} + R_{2})}$
	$i_{3} = \frac{1}{\frac{1}{1 + \frac{R_{3}}{S_{3}}} + \frac{1}{(1 + \frac{S_{3}}{R_{3}}) (1 + \frac{R_{4}}{S_{4}})}}$					$i_{4} = 1 + \frac{\frac{R_{3}}{S_{3}}}{1 + \frac{R_{2}}{S_{2}}}$

Gear RatioTemplate:Efn Template:Efn 5 OrdinaryTemplate:Efn Elementary NotedTemplate:Efn	$i_{5} = \frac{S_{3} R_{2} R_{4} (S_{1} + R_{1}) + S_{2} S_{1} (S_{3} + R_{3}) (S_{4} + R_{4})}{S_{3} R_{4} (S_{1} (S_{2} + R_{2}) + R_{1} R_{2}) + S_{1} S_{2} S_{4} (S_{3} + R_{3})}$
	$i_{5} = \frac{1}{\frac{1}{\frac{(1 + \frac{R_{3}}{S_{3}}) (1 + \frac{S_{4}}{R_{4}})}{1 + \frac{R_{2}}{S_{2}} (1 + \frac{R_{1}}{S_{1}})} + \frac{1}{\frac{1}{1 + \frac{S_{1}}{R_{1}}} + \frac{1 + \frac{S_{2}}{R_{2}}}{1 + \frac{R_{1}}{S_{1}}}}} + \frac{1}{1 + \frac{R_{4}}{S_{4}} + \frac{\frac{R_{2} R_{4}}{S_{2} S_{4}} (1 + \frac{R_{1}}{S_{1}})}{1 + \frac{R_{3}}{S_{3}}}}}$

Gear RatioTemplate:Efn Template:Efn 6 – 8 OrdinaryTemplate:Efn Elementary NotedTemplate:Efn	$i_{6} = \frac{1}{1}$		$i_{7} = \frac{R_{2} (S_{1} + R_{1})}{R_{2} (S_{1} + R_{1}) + S_{1} S_{2}}$				$i_{8} = \frac{R_{2}}{S_{2} + R_{2}}$
	$i_{6} = \frac{1}{1}$		$i_{7} = \frac{1}{1 + \frac{\frac{S_{2}}{R_{2}}}{1 + \frac{R_{1}}{S_{1}}}}$				$i_{8} = \frac{1}{1 + \frac{S_{2}}{R_{2}}}$
Kinetic ratios: torque conversion
Torque RatioTemplate:Efn 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 RatioTemplate:Efn 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 RatioTemplate:Efn 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 RatioTemplate:Efn 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 Template:Efn Template:Efn	Template:Convert 2008		48^[13] 96	48^[13] 96	69^[2] 111	23^[2] 85	2 3	Template:Round Template:Font color	Template:Round
8HP70 Template:Efn Template:Efn	Template:Convert 2008		48^[13] 96	48^[13] 96	69^[2] 111	23^[2] 85	2 3	Template:Round Template:Font color	Template:Font color Template:Efn
Gear	R	1	2	3	4	5	6	7	8
Gear RatioTemplate:Efn	Template:Font color	Template:Round $\frac{108}{23}$	Template:Font color	Template:Round $\frac{162}{77}$	Template:Font color	Template:Font color	Template:Round $\frac{1}{1}$	Template:Font color	Template:Round $\frac{2}{3}$
Step	Template:Font color Template:Efn	1.0000	Template:Font color	1.4879	Template:Font color Template:Efn	Template:Font color	1.2845	Template:Font color	1.2587
Δ StepTemplate:Efn			Template:Font color Template:Efn	1.1787	Template:Font color Template:Efn	Template:Font color Template:Efn	1.0779	Template:Font color Template:Efn
Speed	Template:Font color	1.0000	1.5000	2.2319	Template:Font color	3.6555	4.6957	Template:Font color	7.0435
Δ Speed	Template:Font color	1.0000	0.5000	0.7319	Template:Font color Template:Efn	0.8382	1.0401	Template:Font color Template:Efn	1.4478
Torque RatioTemplate:Efn	–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 $η_{n}$ Template:Efn	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 RatioTemplate:Efn Template:Efn 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 RatioTemplate:Efn Template:Efn 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 RatioTemplate:Efn Template:Efn 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 RatioTemplate:Efn Template:Efn 6 – 8	$i_{6} = \frac{1}{1}$		$i_{7} = \frac{R_{2} (S_{3} + R_{3})}{R_{2} (S_{3} + R_{3}) + S_{2} S_{3}}$				$i_{8} = \frac{R_{2}}{S_{2} + R_{2}}$

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Lawsuits and issues

8L 45 and 8L 90 transmissions manufactured between 2015 and 2019 suffer from two different, unrelated problems.^[14] 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.^[14] Introduction of moisture-resistant transmission fluid in December 2018 largely resolved this issue.^[14] 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.^[14] 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.^[15] As of 2025, the class action had been remanded to the district court for procedural issues.^[14]

Applications

Variants and applications
Make	Model Years	Model	Final Drive Ratio

8L 90
Cadillac	2015–2017	Escalade^[16]	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^[17]	2.41Template:Efn or 2.73Template:Efn
	2015–2019	Corvette (C7) Z06^[18]	2.41
	2019	Corvette (C7) ZR1	2.73
	2015–present	Silverado^[19]	3.23Template:Efn or 3.42Template:Efn
	2015–present	Colorado	3.42
	2016–2018	Camaro SS	2.77
	2017–present	Express Template:Efn
GMC	2015–2017	Yukon Denali · Denali XL	3.23
	2015–present	Sierra^[19]	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

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References

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External links

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↑ ^13.0 ^13.1 8HP 70 Repair Manual · Picture 10106 p. 110 · Saarbruecken 2014 · https://avtgr.ru/upload/data/pdf/zf_instructions/8HP70.pdf
↑ ^14.0 ^14.1 ^14.2 ^14.3 ^14.4 https://www.opn.ca6.uscourts.gov/opinions.pdf/25a0170p-06.pdf This article incorporates public domain text from this source.
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[USA_Info_2018-3] 3.0 ^3.1 Template:Cite web

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

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[70sun1+2-13] 13.0 ^13.1 8HP 70 Repair Manual · Picture 10106 p. 110 · Saarbruecken 2014 · https://avtgr.ru/upload/data/pdf/zf_instructions/8HP70.pdf

[uwu-14] 14.0 ^14.1 ^14.2 ^14.3 ^14.4 https://www.opn.ca6.uscourts.gov/opinions.pdf/25a0170p-06.pdf This article incorporates public domain text from this source.

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GM 8L transmission

Contents

History

2014: 8L 90 M5U

2015: 8L 45 M5N

2023: 8L 80 MFC/N8X and 8L 45 N8R

Key data

Specifications

Planetary gearset concept

Improved fuel economy

Reduced manufacturing complexity

Quality

Lawsuits and issues

Applications

See also

References

External links

Navigation menu

GM 8L transmission

History

2014: 8L 90 M5U

2015: 8L 45 M5N

2023: 8L 80 MFC/N8X and 8L 45 N8R

Key data

Specifications

Planetary gearset concept

Improved fuel economy

Reduced manufacturing complexity

Quality

Lawsuits and issues

Applications

See also

References

External links

Navigation menu

Search