GM 8L transmission

The 8L 45 is an eight-speed automatic transmission built by General Motors debuting in the 2016 Cadillac CT6. It is designed for use in longitudinal engine applications attached to the front-located engine^[1] with a standard bell housing. It is a hydraulic (hydramatic) design sharing much with the 8L 90 transmission.^[2] Estimated weight savings over the heavier duty 8L 90 is 33 pounds (15 kg). Gear ratios used enable a wide 7.0 ratio spread.

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

The 8L 90 is an eight-speed automatic transmission built by General Motors. It is designed for use in longitudinal engine applications either attached to the front-located engine^[1] with a standard bell housing or in the rear of the car adjacent to the differential (as in the Corvette). It is a hydraulic (hydramatic) design. GM also produces a similar design with the smaller 8L 45.

Both gearboxes are based on the layout of the ZF 8HP transmission from 2008, with the only difference being that gearsets 1 and 3 are swapped.^[3]

Specifications

Technical Data

Gear Teeth and Ratios^[a]^[4]			Planetary Gearset: Teeth^[b]				Count	Total	Avg.
Model Type	Version First Delivery		${\displaystyle {S_{1}}}$ ^[c] ${\displaystyle {R_{1}}}$ ^[d]	${\displaystyle {S_{2}}}$ ^[e] ${\displaystyle {R_{2}}}$ ^[f]	${\displaystyle {S_{3}}}$ ^[g] ${\displaystyle {R_{3}}}$ ^[h]	${\displaystyle {S_{4}}}$ ^[i] ${\displaystyle {R_{4}}}$ ^[j]	Brakes Clutches	Ratio Span	Gear Step
Gear ${\displaystyle n}$	R	1	2	3	4	5	6	7	8
Step ${\displaystyle i_{n-1}/i_{n}}$	–R : 1		1 : 2	2 : 3	3 : 4	4 : 5	5 : 6	6 : 7	7 : 8
8L 45 M5N	550 N⋅m (406 lb⋅ft) 2015^[k]		41 79	41 79	41 79	26 94	2 3	7.0107	1.3208
Ratio ${\displaystyle i_{n}}$	−3.9278 ${\displaystyle -{\tfrac {4,187}{1,066}}}$	4.6154 ${\displaystyle {\tfrac {60}{13}}}$	3.0385 ${\displaystyle {\tfrac {79}{26}}}$	2.0648 ${\displaystyle {\tfrac {7,200}{3,487}}}$	1.6583 ${\displaystyle {\tfrac {199}{120}}}$	1.2587 ${\displaystyle {\tfrac {740,760}{588,527}}}$	1.0000 ${\displaystyle {\tfrac {1}{1}}}$	0.8494 ${\displaystyle {\tfrac {9,480}{11,161}}}$	0.6583 ${\displaystyle {\tfrac {79}{120}}}$
Step	0.8510		1.5190	1.4715	1.2451	1.3175	1.2587	1.1773	1.2902
8L 90 M5U	900 N⋅m (664 lb⋅ft)^[5] 2014^[l]		41^[6] 79	46 86	37 73	25 89	2 3	6.9991	1.3204
Ratio ${\displaystyle i_{n}}$	−3.8176 ${\displaystyle -{\tfrac {43,043}{11,275}}}$	4.5600 ${\displaystyle {\tfrac {114}{25}}}$	2.9709 ${\displaystyle {\tfrac {817}{275}}}$	2.0751 ${\displaystyle {\tfrac {12,540}{6,043}}}$	1.6876 ${\displaystyle {\tfrac {,121}{2,442}}}$	1.2700 ${\displaystyle {\tfrac {28,817,100}{22,690,429}}}$	1.0000 ${\displaystyle {\tfrac {1}{1}}}$	0.8455 ${\displaystyle {\tfrac {5,160}{6,103}}}$	0.6515 ${\displaystyle {\tfrac {43}{66}}}$
Step	0.8372		1.5349	1.4317	1.2297	1.3288	1.2700	1.1828	1.2977
Ratio^[m] R & even	${\displaystyle {\tfrac {R_{2}(S_{1}S_{4}-R_{1}R_{4})}{S_{1}S_{4}(S_{2}+R_{2})}}}$		${\displaystyle {\tfrac {R_{2}(S_{4}+R_{4})}{(S_{2}+R_{2})S_{4}}}}$		${\displaystyle 1+{\tfrac {S_{2}R_{3}}{S_{3}(S_{2}+R_{2})}}}$		${\displaystyle {\tfrac {1}{1}}}$		${\displaystyle {\tfrac {R_{2}}{S_{2}+R_{2}}}}$
Ratio^[m] odd		${\displaystyle {\tfrac {S_{4}+R_{4}}{S_{4}}}}$	${\displaystyle {\tfrac {(S_{3}+R_{3})(S_{4}+R_{4})}{S_{4}R_{3}+S_{3}(S_{4}+R_{4})}}}$		${\displaystyle {\tfrac {S_{3}R_{2}R_{4}(S_{1}+R_{1})+S_{2}S_{1}(S_{3}+R_{3})(S_{4}+R_{4})}{S_{3}R_{4}(S_{1}(S_{2}+R_{2})+R_{1}R_{2})+S_{1}S_{2}S_{4}(S_{3}+R_{3})}}}$			${\displaystyle {\tfrac {R_{2}(S_{1}+R_{1})}{R_{2}(S_{1}+R_{1})+S_{1}S_{2}}}}$
8HP 70 ^[n]^[o]	700 N⋅m (516 lb⋅ft) · 2008		48^[7] 96	48^[7] 96	69^[8] 111	23^[8] 85	2 3	7.0435	1.3216
Ratio ${\displaystyle i_{n}}$	−3.2968 ${\displaystyle -{\tfrac {1,744}{529}}}$	4.6957 ${\displaystyle {\tfrac {108}{23}}}$	3.1304 ${\displaystyle {\tfrac {72}{23}}}$	2.1039 ${\displaystyle {\tfrac {162}{77}}}$	1.6667 ${\displaystyle {\tfrac {5}{3}}}$	1.2845 ${\displaystyle {\tfrac {8,826}{6,871}}}$	1.0000 ${\displaystyle {\tfrac {1}{1}}}$	0.8392 ${\displaystyle {\tfrac {120}{143}}}$	0.6667 ${\displaystyle {\tfrac {2}{3}}}$
Step	0.7021		1.5000	1.4879	1.2623	1.2975	1.2845	1.1917	1.2587
Ratio^[p] R & even	${\displaystyle {\tfrac {R_{2}(S_{3}S_{4}-R_{3}R_{4})}{S_{3}S_{4}(S_{2}+R_{2})}}}$		${\displaystyle {\tfrac {R_{2}(S_{4}+R_{4})}{(S_{2}+R_{2})S_{4}}}}$		${\displaystyle 1+{\tfrac {S_{2}R_{1}}{S_{1}(S_{2}+R_{2})}}}$		${\displaystyle {\tfrac {1}{1}}}$		${\displaystyle {\tfrac {R_{2}}{S_{2}+R_{2}}}}$
Ratio odd^[p]		${\displaystyle {\tfrac {S_{4}+R_{4}}{S_{4}}}}$	${\displaystyle {\tfrac {(S_{1}+R_{1})(S_{4}+R_{4})}{S_{4}R_{1}+S_{1}(S_{4}+R_{4})}}}$		${\displaystyle {\tfrac {S_{1}R_{2}R_{4}(S_{3}+R_{3})+S_{2}S_{3}(S_{1}+R_{1})(S_{4}+R_{4})}{S_{1}R_{4}(S_{3}(S_{2}+R_{2})+R_{2}R_{3})+S_{2}S_{3}S_{4}(S_{1}+R_{1})}}}$			${\displaystyle {\tfrac {R_{2}(S_{3}+R_{3})}{R_{2}(S_{3}+R_{3})+S_{2}S_{3}}}}$

1. Differences in gear ratios have a measurable, direct impact on vehicle dynamics, performance, waste emissions as well as fuel mileage
2. Planetary gearset orientation: (1) Planetary gearset 1 is on the input (turbine) side (with gearset 1 and 3 swapped) (2) Output shaft is carrier 4 (planetary gear carrier of gearset 4)
3. Sun 1: sun gear of gearset 1
4. Ring 1: ring gear of gearset 1
5. Sun 2: sun gear of gearset 2
6. Ring 2: ring gear of gearset 2
7. Sun 3: sun gear of gearset 3
8. Ring 3: ring gear of gearset 3
9. Sun 4: sun gear of gearset 4
10. Ring 4: ring gear of gearset 4
11. Model year 2016
12. Model year 2015
13. Adjusted formulas with gearset 1 and 3 swapped
14. without generation designation
15. First transmission on the market to use the dedicated 8-speed layout · gearset 1 and 3 not swapped
16. Original formulas with gearset 1 and 3 not swapped

Features

	8L 45 M5N^[9]	8L 90 M5U · N8X^[10]
Input Capacity
Maximum engine power	308 bhp (230 kW)^[a]	420 bhp (310 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 (5,400 kg)^[a]	22,500 lb (10,200 kg)^[b]
Structure
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

1. based on 2020 Chevrolet Colorado Z71 2WD Crew Cab · Short Bed
2. General Motors estimate
3. General Motors Powertrain

Applications

8L 45

Make	Model Years	Model	Final Drive Ratio
Cadillac	2016–2019	ATS
	2016–2019	CTS
	2020–present	CT4
	2016–present	CT6
Chevrolet	2016–2019	Camaro
	2017–present	Colorado
GMC	2017–present	Canyon

8L 90

Make	Model Years	Model	Final Drive Ratio
Cadillac	2015–2017	Escalade^[11]	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^[12]	2.41^[a] or 2.73^[b]
	2015–2019	Corvette (C7) Z06^[13]	2.41
	2015–present	Silverado^[14]	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^[14]	3.23
	2015–present	Canyon	3.42
	2017–present	Savana^[d]

1. Standard
2. Z51
3. Maximum Trailering Package
4. 2.8 L diesel engine and 4.3 L gas engine only

Lawsuits

The 8L 90 is 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]

See also

• List of GM transmissions

References

1. "USA Information Guide Model Year 2018" (PDF). Retrieved 15 July 2019.
2. "Cadillac Introduces New 8-Speed Automatic on CT6". Cadillac Media USA. Cadillac Media USA. 20 March 2015. Retrieved 20 March 2015.
3. "Timur Apakidze · Saturation Dive: The GM 8L 90 8-Speed Transmission". TTAC: The Truth About Cars. 23 April 2014. Retrieved 12 April 2024.
4. . www.gm.com. General Motors. 20 August 2014. Archived from the original on 22 December 2014. Retrieved 21 August 2014.
5. "Transmission Repair Cost Guide". Retrieved 15 July 2019.
6. "WIT · Whatever It Takes · Automatic Transmission Parts Catalog 2018+2019 Page 268". Retrieved 15 July 2019.
7. 8HP 70 Repair Manual · Picture 10106 p. 110 · Saarbruecken 2014 · https://avtgr.ru/upload/data/pdf/zf_instructions/8HP70.pdf
8. "Timur Apakidze · Saturation Dive: ZF 8-Speed Automatic". TTAC: The Truth About Cars. 11 March 2014. Retrieved 7 July 2019.
9. https://poweredsolutions.gm.com/products/8l45-8-speed-transmission/
10. https://poweredsolutions.gm.com/products/8l90-8-speed-transmission/
11. "2015 Cadillac Escalade Updated with 8L90 8-Speed Automatic and More Tech [Photo Gallery]". 11 August 2014. Retrieved 12 August 2014.
12. "Chevrolet Confirms 2015 Corvette Stingray To Utilize 8L90 Eight-Speed Gearbox". Retrieved 9 April 2014.
13. "Supercharged 2015 Chevy Corvette Z06 takes the C7 beyond the ZR1 [w/video]". Retrieved 25 January 2014.
14. "GM confirms 2015 Silverado, Sierra to get 8-speed automatic". Retrieved 18 June 2014.
15. "Class Action Lawsuit Filed Over Alleged Shifting Defect in Certain General Motors Transmissions". 19 December 2018. Retrieved 2 February 2019.

External links

• General Motors Powertrain Division
• https://gmauthority.com/blog/gm/gm-transmissions/m5n/
• https://gmauthority.com/blog/gm/gm-transmissions/m5u/