Engineering:GM 8L transmission

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Short description: Automatic transmission family produced by General Motors
8L 45 · 8L 90
Overview
ManufacturerGeneral Motors
Production2014–
Body and chassis
Class8-speed longitudinal automatic transmission
RelatedZF 8HP
Chronology
Predecessor6L 45 · 6L 50 · 6L 80 · 6L 90
Successor10L 80 · 10L 90 · 10L 1000

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.

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.

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.[3]

Specifications

Gear Teeth and Ratios[4] Planetary Gearset: Teeth[lower-alpha 1] Count Total Avg.
Model
Type 		Version
First Delivery 		[math]\displaystyle{ {S_1} }[/math][lower-alpha 2]
[math]\displaystyle{ {R_1} }[/math][lower-alpha 3] 		[math]\displaystyle{ {S_2} }[/math][lower-alpha 4]
[math]\displaystyle{ {R_2} }[/math][lower-alpha 5] 		[math]\displaystyle{ {S_3} }[/math][lower-alpha 6]
[math]\displaystyle{ {R_3} }[/math][lower-alpha 7] 		[math]\displaystyle{ {S_4} }[/math][lower-alpha 8]
[math]\displaystyle{ {R_4} }[/math][lower-alpha 9] 		Brakes
Clutches 		Ratio
Span 		Gear
Step
Gear R 1 2 3 4 5 6 7 8
8L 45
M5N 		550 N⋅m (406 lb⋅ft)
2015[lower-alpha 10] 		41
79 		41
79 		41
79 		26
94 		2
3 		7.0107 1.3208
Ratio –3.9278 4.6154 3.0385 2.0648 1.6583 1.2587 1.0000 0.8494 0.6583
8L 90
M5U 		900 N⋅m (664 lb⋅ft)[5]
2014[lower-alpha 11] 		41[6]
79 		46
86 		37
73 		25
89 		2
3 		6.9991 1.3204
Ratio –3.8176 4.5600 2.9709 2.0751 1.6876 1.2700 1.0000 0.8455 0.6515
Ratio
R & even 		[math]\displaystyle{ \tfrac{R_2 (S_3 S_4-R_3 R_4 )}{S_3 S_4 (S_2+R_2 )} }[/math] [math]\displaystyle{ \tfrac{R_2 (S_4+ R_4 )}{(S_2+ R_2 ) S_4} }[/math] [math]\displaystyle{ 1+\tfrac{S_2 R_1}{S_1 (S_2+ R_2 )} }[/math] [math]\displaystyle{ \tfrac{1}{1} }[/math] [math]\displaystyle{ \tfrac{R_2 }{S_2 + R_2 } }[/math]
Ratio
odd 		[math]\displaystyle{ \tfrac{S_4+ R_4}{S_4} }[/math] [math]\displaystyle{ \tfrac{(S_1+ R_1 ) (S_4+ R_4 )}{S_4 R_1+ S_1 (S_4+ R_4 )} }[/math] [math]\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 )} }[/math] [math]\displaystyle{ \tfrac{R_2 (S_3+ R_3 )}{R_2 (S_3+ R_3 )+ S_2 S_3 } }[/math]
  1. ↑ Planetary gearset orientation: (1) Planetary gearset 1 is on the input (turbine) side (2) Output shaft is carrier 4 (planetary gearset carrier of gearset 4)
  2. ↑ Sun 1: sun gear of gearset 1
  3. ↑ Ring 1: ring gear of gearset 1
  4. ↑ Sun 2: sun gear of gearset 2
  5. ↑ Ring 2: ring gear of gearset 2
  6. ↑ Sun 3: sun gear of gearset 3
  7. ↑ Ring 3: ring gear of gearset 3
  8. ↑ Sun 4: sun gear of gearset 4
  9. ↑ Ring 4: ring gear of gearset 4
  10. ↑ Model year 2016
  11. ↑ Model year 2015

Applications

8L 45

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

8L 90

Model years Make and model Final drive ratio
2015–2017 Cadillac Escalade[7] 3.23
2015–2019 Chevrolet Corvette (C7) Stingray[8] 2.41 (std)
2.73 (Z51)
2015–2019 Chevrolet Corvette (C7) Z06[9] 2.41
2015–present Chevrolet Silverado/GMC Sierra[10] 3.23 (std.)
3.42 (Max Trailering Package)
2015–2017 GMC Yukon Denali/Denali XL 3.23
2016–present Cadillac ATS-V 2.85
2016–present Cadillac CTS-V 2.85
2016–present Cadillac CT6 3.27
2016–2018 Chevrolet Camaro SS 2.77
2017–present Chevrolet Express/GMC Savana (2.8L
diesel engine/4.3L gas engine only)
2015–present Chevrolet Colorado/GMC Canyon 3.42

See also

References

  1. ↑ 1.0 1.1 "USA Information Guide Model Year 2018". https://www.gmpowertrain.com/assets/docs/2018R_F3F_Information_Guide_031918.pdf. 
  2. ↑ "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. 
  3. ↑ "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. 
  4. ↑ "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. 
  5. ↑ "Transmission Repair Cost Guide". https://www.transmissionrepaircostguide.com/8l90/. 
  6. ↑ "WIT · Whatever It Takes · Automatic Transmission Parts Catalog 2018+2019 Page 268". https://www.wittrans.com/catalog. 
  7. ↑ "2015 Cadillac Escalade Updated with 8L90 8-Speed Automatic and More Tech [Photo Gallery"]. 11 August 2014. http://www.autoevolution.com/news/2015-cadillac-escalade-updated-with-8l90-8-speed-automatic-and-more-tech-photo-gallery-85117.html. 
  8. ↑ "Chevrolet Confirms 2015 Corvette Stingray To Utilize 8L90 Eight-Speed Gearbox". http://gmauthority.com/blog/2014/04/chevrolet-confirms-2015-corvette-stingray-to-utilize-8l90-eight-speed-gearbox/. 
  9. ↑ "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/. 
  10. ↑ "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/. 

External links



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