Cadillac Introduces New 8-Speed Automatic on CT6

Patented design offers seamless performance, supports stop/start tech

2015-03-20


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DETROIT – Cadillac advances its legacy of technologically driven performance and luxury with the Hydra-Matic 8L45 paddle-shift eight-speed automatic transmission, which debuts with the all-new 2016 Cadillac CT6.

Matched with the next-generation 3.6L V-6, the 8L45 transmission is based on the same acclaimed General Motors-designed eight-speed automatic family introduced on the Corvette Stingray – with the higher-capacity 8L90 version paired with the CT6’s available 3.0L twin-turbo V-6 engine.

“The shift performance of the new 8L45 paddle-shift eight-speed automatic transmission complements the CT6’s new threshold for efficient luxury to help take it to an even higher level,” said Bill Goodrich, assistant chief engineer for eight-speed automatic transmissions. “The shifts are quick and nearly imperceptible, establishing a benchmark for Cadillac.”

The 8L45 eight-speed shares the architecture and design features of the Hydra-Matic 8L90 transmission, but it is scaled and calibrated for the performance envelope of the new 3.6L V-6. It also incorporates components to support the engine’s stop/start technology.

Stop/start shuts down the engine to reduce fuel consumption when vehicle comes to a complete stop, and it automatically restarts the engine when the driver takes his or her foot off the brake pedal.

In addition to stop/start efficiency, the 8L45 eight-speed’s wide 7.0 overall ratio and numerically lower top gear offer an up to a GM estimated 5 percent fuel economy benefit over a comparable six-speed automatic transmission.

A numerically higher 4.62 first gear ratio also helps drivers start off more confidently, with a greater feeling of immediate performance.

“The 8L45 was designed to enhance the CT6’s driving experience, offering a strong balance between performance and efficiency,” said Goodrich. “Perhaps its best attribute will be that customers really won’t notice it – they’ll simply enjoy the CT6’s seamless, smooth driving experience and on-demand performance.”

Compact, mass-efficient design
With four simple gearsets for optimal efficiency and five clutches (two brake clutches and three rotating clutches), creative packaging enables GM’s eight-speed automatic to fit the same space as the previous six-speed automatic, with a lower weight.

The new 8L45’s smaller package size enables approximately 33 pounds (15 kg) mass saving compared to the 8L90 eight-speed – a transmission that was already lighter than GM’s 6L80 six-speed automatic.

Smaller steps between gears, compared to a six-speed transmission, keep the engine within its optimal rpm range, making the most of its horsepower and torque to optimize performance and efficiency.

Ratios compared: Hydra-Matic 8L45 vs. 8L90


Type:

8L45 eight-speed automatic

8L90 eight-speed automatic

Gear ratios (:1)

 

 

     First:

4.62

4.56

     Second:

3.04

2.97

     Third:

2.07

2.08

     Fourth:

1.66

1.69

     Fifth:

1.26

1.27

     Sixth:

1.00

1.00

     Seventh:

0.85

0.85

     Eighth:

0.66

0.65

     Reverse:

3.93

3.82


Additionally, friction-reducing design features – including synthetic fluid – and lower spin losses via a powerflow that uses only two open clutches per gear and an off-axis binary vane pump contribute further to efficiency.

The torque converter design with turbine damper enhances refinement, particularly during low-speed gear changes, for smoother performance.

Architectural features
More than 1,100 computer-aided engineering analyses were made during the development of the Hydra-Matic eight-speed transmission family – resulting in more than two dozen patents – to ensure strength, durability, performance and refinement.

Architectural highlights include:

  • A one-piece case with an integral bell housing for enhanced powertrain stiffness
  • The grounding clutches are located rearward of the middle of the structure, outside the gearsets, and are splined to the case, eliminating the need for a the center support, which reduces weight
  • The rotating clutches are located near the front of the transmission, with short oil feed channels, to support very fast shifts
  • A unique oil-storage accumulator is incorporated to support stop/start technology. It ensures the clutches have oil for immediate take-off when the engine is re-started
  • World-class shift time quickness and responsiveness are accomplished with a Gen II controls system, which works with variable force solenoid technology and three internal Hall Effect speed sensors
  • The transmission controller is mounted externally and its processor executes hundreds of calculations and commands every 6.25 milliseconds.

The Hydra-Matic 8L45 and 8L90 transmissions are built at GM’s Toledo, Ohio, and Silao, Mexico, transmission facilities. They will also be offered in the 2016 Cadillac CTS and ATS, including CTS-V and ATS-V.

 

8L45 eight-speed automatic

8L90 eight-speed automatic

2016 CT6

2.0L Turbo I-4 and 3.6L V-6

3.0L Twin Turbo V-6

2016 CTS & CTS-V

2.0L Turbo I-4 and 3.6L V-6

6.2L Supercharged V-8

2016 ATS & ATS-V

2.5L, 2.0L Turbo I-4 and 3.6L V-6

3.6L Twin Turbo V-6

 

FAST FACT: In 1941, Cadillac was one of the first major automakers to offer a fully automatic transmission. That early Hydra-Matic transmission was also paired with Cadillac V-8 engines to drive M24 Chaffee tanks during World War II.

Cadillac has been a leading luxury auto brand since 1902. Today Cadillac is growing globally, driven by an expanding product portfolio featuring dramatic design and technology. More information on Cadillac appears at www.cadillac.com. Cadillac's media website with information, images and video can be found at media.cadillac.com

The Hydra-Matic 8L45 eight-speed automatic transmission used in the Cadillac CT6 shares the architecture and design features of the Hydra-Matic 8L90 transmission, but it is scaled and calibrated for the performance envelope of the new 3.6L V-6. It also incorporates components to support the engine’s stop/start technology.

The Hydra-Matic 8L45 eight-speed automatic transmission used in the Cadillac CT6 shares the architecture and design features of the Hydra-Matic 8L90 transmission, but it is scaled and calibrated for the performance envelope of the new 3.6L V-6. It also incorporates components to support the engine’s stop/start technology.

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