GM 8L45 transmission

The 8L45 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 8L90 transmission.^[2] Estimated weight savings over the heavier duty 8L90 is 33 pounds (15 kg). Gear ratios used enable a wide 7.0 ratio spread.

Specifications

Gear Teeth and Ratios			Planetary Gearset: Teeth				Count	Total	Avg.
Model Type	Version First Delivery		Sun 1 ${\displaystyle {S_{1}}}$ Ring 1 ${\displaystyle {R_{1}}}$	Sun 2 ${\displaystyle {S_{2}}}$ Ring 2 ${\displaystyle {R_{2}}}$	Sun 3 ${\displaystyle {S_{3}}}$ Ring 3 ${\displaystyle {R_{3}}}$	Sun 4 ${\displaystyle {S_{4}}}$ Ring 4 ${\displaystyle {R_{4}}}$	Brakes Clutches	Ratio Span	Gear Step
Gear	R	1	2	3	4	5	6	7	8
8L45 M5T	550 N⋅m (406 lb⋅ft) 2015		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
8L90 M5U	900 N⋅m (664 lb⋅ft)[3] 2014		41[4] 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	${\displaystyle {\tfrac {R_{2}(S_{3}S_{4}-R_{3}R_{4})}{S_{3}S_{4}(S_{2}+R_{2})}}}$		${\displaystyle {\tfrac {R_{2}(S_{4}+R_{4})}{(S_{2}+R_{2})S_{4}}}}$		${\displaystyle 1+{\tfrac {S_{2}R_{1}}{S_{1}(S_{2}+R_{2})}}}$		${\displaystyle {\tfrac {1}{1}}}$		${\displaystyle {\tfrac {R_{2}}{S_{2}+R_{2}}}}$
Ratio odd		${\displaystyle {\tfrac {S_{4}+R_{4}}{S_{4}}}}$	${\displaystyle {\tfrac {(S_{1}+R_{1})(S_{4}+R_{4})}{S_{4}R_{1}+S_{1}(S_{4}+R_{4})}}}$		${\displaystyle {\tfrac {S_{1}R_{2}R_{4}(S_{3}+R_{3})+S_{2}S_{3}(S_{1}+R_{1})(S_{4}+R_{4})}{S_{1}R_{4}(S_{3}(S_{2}+R_{2})+R_{2}R_{3})+S_{2}S_{3}S_{4}(S_{1}+R_{1})}}}$			${\displaystyle {\tfrac {R_{2}(S_{3}+R_{3})}{R_{2}(S_{3}+R_{3})+S_{2}S_{3}}}}$

Applications

References

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This page was last edited on 22 January 2024, at 00:02