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Someone posted this on the Saturnalia forum....thought it was worth sharing...



2007 Hydra-Matic 6T70 (MH2-FWD)
Hydra-Matic 6T75 (MY9-FWD, MH6-AWD)

2007 Model Year Summary
Hydra-Matic 6T70 / 6T75 six-speed automatic front- or all-wheel-drive Car / Truck transmission

● All-new Six-Speed Automatic Transmission
● New Car Applications: Pontiac G6, Saturn Aura (MH2)
● New Truck Application: Saturn Outlook, (MY9, MH6)
● Contemporary On-Axis Design
● Advanced Clutch-To-Clutch Shift Operation
● Tuned For Quick Launch And Fuel Efficient Cruising
● Compact Dimensions Aid Packaging
● Hyper-elliptical Torque Converter Saves Space
● Vane-Type Variable Capacity Pump Aids Efficiency
● Ground And Honed Gears For Precision Fit And Lower NVH Levels
● Unique Input Shaft Eliminates Costly Machining And Adds Strength


FULL DESCRIPTIONS OF NEW OR CHANGED FEATURES

ALL-NEW SIX-SPEED AUTOMATIC TRANSMISSION
Two versions of the new transverse six-speed automatic transaxle debut for the 2007 model year, featuring a notably wide ratio spread, and the ability to handle different levels of engine torque and vehicle applications (see specs).

NEW CAR APPLICATIONS: PONTIAC G6, SATURN AURA (MH2)
The Saturn Aura sedan is scheduled to go on sale in the summer of 2006 using the 6T70, which is mated to the 3.6L V6 VVT, and is rated to handle 280 lb. ft. of engine torque. The 6T70 is available in front-drive applications (MH2) in both the Aura and the Pontiac G6.

NEW TRUCK APPLICATION: SATURN OUTLOOK (MY9, MH6)
The new Hydra-Matic 6T75 transmission debuted in the Saturn Outlook body-frame-integral (BFI) SUV, which was scheduled to begin production midway through 2006. It is mated to the 3.6L V6 VVT and is capable of handling 300 lb. ft. of torque from the engine. Two variations are used, the front-drive configuration (MY9) and the all-wheel-drive configuration (MH6).

INNOVATIVE ON-AXIS DESIGN
Instead of “folding” the transmission around the end of a transversely mounted engine, which has been one of the dominant GM transaxle design conventions, the new Hydra-Matic 6T70 and 6T75 contain all of their gearing in line with the crankshaft centerline of the engine. The advantages of this layout can translate to a shorter overall vehicle length, more interior room in a vehicle, and lower powertrain height.

ADVANCED CLUTCH-TO-CLUTCH SHIFT OPERATION
To save space compared to “freewheeling” gear change mechanisms, the shifts are accomplished by applying and disengaging clutches simultaneously during each gear change. Sophisticated electronics help enable the precision needed to time the clutches for each shift. The first-to-second gear shift uses a freewheeling mechanism, however, which tends to be smoother during shifts between gears with large ratio differences, such as first and second gears.

TUNED FOR QUICK LAUNCH AND FUEL EFFICIENT CRUISING
Because of the wide ratio spread, first gear is a very high ratio, which provides brisk acceleration from a stop. Sixth, however, is an overdrive ratio, which keeps the engine revolutions as low as possible for highway cruising, reducing engine friction losses and improving fuel economy.

COMPACT DIMENSIONS AID PACKAGING
State-of-the-art dimensions enable spacious packaging and enhance potential safety design opportunities. In addition, styling opportunities for lower hood lines are also enabled by the compact dimensions of the 6T70 and 6T75.

HYPER-ELLIPTICAL TORQUE CONVERTER SAVES SPACE
The 258mm torque converter uses a single plate lockup clutch and features an oval cross-section shape, called “hyper-elliptical”. This shape reduces the thickness of the torque converter, reducing the space it needs and keeping the overall width of the engine and transmission as narrow as possible for packaging advantages. The single-plate lockup clutch makes use of GM’s electronic controlled capacity clutch (ECCC) technology to help dampen engine vibrations and ensure smooth operation.

VANE-TYPE VARIABLE CAPACITY PUMP AIDS EFFICIENCY
A chain-driven, off-axis fluid pump provides hydraulic pressure for the shift events and lubrication. The pump features vanes which can vary its output, this way optimizing the amount of energy the pump needs to operate. Internal tests have demonstrated improved powertrain efficiency with the variable capacity pump.

GROUND AND HONED GEARS FOR PRECISION FIT AND LOWER NVH LEVELS
To minimize gear noise as well as vibration, the helical gears are ground and honed to ensure exact dimensions and tolerances. With closer tolerances, the gears are less prone to characteristic whining or humming, and overall the transmission operates as quietly as possible.

UNIQUE INPUT SHAFT BUSHINGS ELIMINATE MACHINING
The input shaft requires no machining for grooves to contain fluid seals, which allows the shaft to retain maximum strength for its size and minimize cost.


LOW MAINTENANCE
The 6T50 is filled for life with DEXRON®-VI premium fluid, which during normal use need not be replaced. DEXRON®-VI is validated to improve durability and shift stability over the life of the transmission. DEXRON® VI, was developed to have a more consistent viscosity profile; a more consistent shift performance in extreme conditions; and less degradation over time. Internal GM tests have demonstrated DEXRON® VI delivers more than twice the durability and stability in friction tests compared to existing fluids. The DEXRON®-VI fluid was designed specifically and validated for the new family of GM six-speed automatic transmissions.


OVERVIEW
The concept behind the new six-speed front- and all-wheel-drive transaxle family is to enable compact packaging not possible before with a powerful transverse powertrain layout. The gearsets are on the same axis as the engine crankshaft centerline, which makes the entire powertrain unit much shorter fore-to-aft. This allows chassis designers the ability to enhance crush zones, to increase interior space, and lower the hood line of the vehicle compared to a conventional off-axis transaxle.

Two variations of the six-speed automatic transaxle are being introduced for the 2007 Model Year, the 6T70 and 6T75. The primary difference is the 6T75 has greater torque handling capability (see specs). The input gearset of the 6T75 uses five pinion gears, versus four pinions for the 6T70. In addition, the case of the 6T75 is slightly larger and includes a heavier ribbed case for strength.

Three planetary gearsets are used with three stationary clutches and two rotating clutches, which save space compared to freewheeling designs. Freewheeling mechanisms allow perfect timing between shifts, but also take up more space and add more components to the transmission. However, due to the electronic controls, the clutch-to-clutch concept of the 6T70/75 delivers the same accurate shift timing. Gear changes from second to sixth gear ratios are accomplished with a precise clutch-to-clutch action, where the clutch is engaged in one gear at exactly the same time it is released in another. The first-to-second upshift, 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.

Adaptive shift controls include automatic grade braking, which commands the transmission to remain in a lower gear if the vehicle is decelerating or coasting on a downgrade. This takes advantage of engine braking to prevent unwanted acceleration. This reduces the need for the driver to brake during a hill descent. The control module receives input that monitors brake pedal usage, vehicle acceleration rate, throttle position, and even whether a trailer is connected to the vehicle.

The wide overall ratio spread of 6.04:1 allows a “steep” first gear, as well as a “tall” overdrive top gear for low-rpm highway cruising. Acceleration is maximized, as is fuel economy. Engine noise is also lower during cruising. Sixth gear is a tall “overdrive” gear, for example.

The transmission control module in the 6T70 and 6T75 allow the modules to exist reliably inside the transmission, where temperatures remain mostly constant compared to a body-mounted module. The smaller size of the module means the transmission case can be more compact. The transmission and module are assembled together, so no additional connections 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 all future global applications and the design can accommodate different modules. All of the module strategy is developed by GM Powertrain.

The Hydra-Matic 6T70 / 6T75 was co-developed with Ford Motor Company, a process which reduced development time and cost by up to 50 percent for major components. The Hydra-Matic six-speed, however, is engineered exclusively for GM Powertrain applications. The Hydra-Matic 6T70 / 6T75 is produced in Warren, Michigan
 

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Wow, tons of details in that writeup. Thanks for posting!
 
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