2010 Hydra-Matic 6T70 (MH2-FWD, MH4- AWD)
Hydra-Matic 6T75 (MY9-FWD, MH6-AWD)
2010 Model Year Summary
Hydra-Matic 6T70 / 6T75 six-speed automatic front- or all-wheel-drive Car / Truck transmission
Six-Speed FWD/AWD Automatic Transmission
New Car Applications:
Buick LaCrosse (6T70 MH2, MH4)
New Truck Applications:
Cadillac SRX (6T70 MH2, MH4)
Chevy Equinox (6T70 MH2, MH4)
GMC Terrain (6T70 MH2, MH4)
New Engine Application:
3.0L V-6 VVT DI (LF1) (LaCrosse, Equinox and SRX)
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
Car applications:
The 6T70 (MH2) will continue to be offered in the Chevrolet Malibu and mated to the 3.6L V-6 VVT (LY7) for the 2010 model year. Added to the car application line up is the New Buick LaCrosse with two engine offerings: the 3.0L V-6 VVT DI (LF1) engine and the 3.6L V-6 VVT DI (LLT) engine.
Truck applications:
The 6T70 (MH2,MH4) will be available in 2010 in the new Chevy Equinox, GMC Terrain and Cadillac SRX matched to the 3.0L V-6 VVT DI ( LF1) engine.
The 6T75 (MY9, MH6) models are available in the GMC Acadia, Buick Enclave and Chevrolet Traverse models mated with the 3.6L V-6 VVT DI (LLT) engine.
Carryover from model year 2009 features and benefits are listed below:
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 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 (6.04:1), 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 246mm torque converter uses a single 258mm 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 6T70/75 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 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 available for the 2010 Model Year, the 6T70 and 6T75. The primary difference is the 6T75 has greater torque handling capability (see specs).
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, utilizes a freewheeling or one-way clutch, where the second gear clutch engages while the first gear one-way clutch spins freely. This arrangement provides smooth operation at low 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.
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 is produced in Warren, Michigan and Ramos, Mexico.