6 Guns Shifting into Overdrive

The 2009 Cadillac CTS-V arrived with a supercharged 6.2L OHV V8 engine, the mighty LSA.  It also brought back an ‘expected’ Cadillac feature to the CTS-V line — an optional Automatic transmission.  But wait, what automatic transmission can be strapped to the back of a freight train like the LSA and live?  Enter the 6L90 Heavy Duty Automatic 6 speed Transmission to the world of sports cars.

2010 Hydra-Matic 6L90 (MYD) Six Speed RWD/AWD Automatic Transmission for Cadillac CTS-V

Overview

The Hydra-Matic 6L90 is six-speed automatic transmission for rear- and four-wheel-drive trucks, designed with modular flexibility and compatibility with advanced electronic controls. It is a heavy-duty version of the 6L80 six-speed automatic, with a strengthened input gear-set which has two additional pinion gears for six total, and a strengthened output gearset, that uses wider gears than the 6L80.  The 6L90 flexibility extends to the clutches where the 6L90 has one more clutch plate than the 6L80 in each clutch for heavy duty applications.

The 6L90 has the capability for adaptive shift controls and other features such as grade braking, and Driver Shift Control with tap up/tap down shifting as found in the CTS-V. A wide overall ratio spread of 6.04:1 allows a “steep” first gear, as well as very “tall” overdrive top gear for low-rpm highway cruising. With this wide ratio spread, acceleration is maximized, as is fuel economy. Engine noise is also lower during cruising. Both fifth and sixth gears are “overdrive” gears, for example.

As in the 6L80, gear changes from second to sixth gears are accomplished with clutch-to-clutch control, where an oncoming clutch is engaged and an “offgoing” clutch is released in a precise manner to achieve the ratio change. The first-to-second up-shift, however, is a freewheeling action, where the second gear clutch engages while the first gear one-way clutch spins freely. This allows a greater degree of smoothness at lower vehicle speeds. The clutch-to-clutch shifting and single freewheeler allows significant reductions in packaging requirements.

Advances in transmission control modules allow the modules to exist reliably inside the transmission, where temperatures remain fairly constant compared to a body-mounted module. The transmission and module are assembled together, so no additional steps are necessary during vehicle assembly.

The 32-bit transmission control module (TCM) monitors transmission performance and compensates for normal wear in components such as clutch plates, so transmission performance remains consistent for the life of the transmission. The control module also “tests” the components of the transmission following assembly to optimize the interaction of the components. The module is compatible with future global applications.

2010 Hydra-Matic 6L90 Transmission ( MYD )
Type: Six speed RWD / AWD, electronically controlled automatic overdrive transmission with torque converter clutch. Clutch-to-clutch architecture, with integral Electro / Hydraulic Controls Module
Maximum engine power: 452 bhp ( 337 kW ), Diesel: 300bhp ( 223kW ) – Truck
555 bhp ( 414 kW ) – Passenger car
Maximum engine torque: 531 lb-ft ( 720 Nm ), Diesel: 520 lb-ft ( 705 Nm ) – Truck
550 lb-ft ( 746 Nm ) – Passenger car
Maximum gearbox torque: 885 lb-ft ( 1200 Nm )
Gear ratios: MYD
First: 4.03
Second: 2.36
Third: 1.53
Fourth: 1.15
Fifth: 0.85
Sixth: 0.67
Reverse: -3.06
Maximum shift speed 6200 rpm
Maximum Validated Weights: ( Target ) GVW: 15000 lb ( 6803 kg ), GCVW: 21000 lb ( 9525 kg )
7-position quadrant: P, R, N, D, X, X, X ( X = available calibratable range position )
Case description: 3-piece ( Bell, main, extension )
Case material: die cast aluminum
Shift pattern: (2) Three-way on/off solenoids
Shift quality: Five variable bleed solenoid
Torque converter clutch: Variable Bleed Solenoid ECCC
Converter size: 300mm ( reference )
Fluid type: DEXRON® VI
Fluid capacity: w/ 300mm converter 300mm: 13.0L ( 10.8kg )
Transmission weight: w/ 300mm converter Wet: 109kg ( 240lb ) estimated
Pressure taps available: line pressure
Assembly Site: GMPT Ypsilanti, MI

GMPT Toledo, OH

GMPT Silao, MX
Applications: Chevrolet Suburban H.D.
GMC Yukon XL H.D.
Chevrolet Silverado HD
GMC Sierra HD

Cadillac CTS-V

Chevrolet Express

GMC Savana
Available Control Features: Multiple Shift Patterns ( Selectable )

Driver Shift Control ( Tap Up / Tap Down )

Enhanced Performance Algorithm Shifting ( PAS )

Selectable Tow / Haul Mode

Engine Torque Management On All Shifts

Altitude and Temperature Compensation

Adaptive Shift Time

Neutral Idle

Reverse Lockout

Automatic Grade Braking
Additional Features: OBDII / EOBD

Integral Electro/Hydraulic Controls Module ( Tehcm )

Control Interface Protocol – GMLAN

So, that begs the question — was the transmission rated to fit the engine output, or is the engine tuned to that output level because that is the maximum capability of the transmission?

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