2007 Hydra-Matic 6T70 (MH2-FWD)

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


2007 6T75 ( MH6 AWD,MY9 FWD ) 04/19/06
Type:  Six speed front-wheel-drive & AWD, electronically controlled, automatic overdrive transaxle with an electronically controlled torque converter clutch.
Engine range: 4.6L
Maximum engine torque:  301 lb-ft (406 Nm)
Maximum gearbox torque: 463 lb-ft (515Nm)
Gear ratios:   
First  4.48
Second  2.87
Third: 1.84
Fourth: 1.41
Fifth 1
Sixth 0.74
Reverse:  2.88
Final Drive Ratio: 3.16
Maximum shift speed: 1-2 6800 rpm
2-3 6800 rpm
3-4 6800 rpm
Maximum validated gross vehicle weight:  6384 lb
Shifter Posistions: P, R, N, M
Case material:  die cast aluminum
Shift pattern: 4 VBS Solenoids
Shift quality: Variable Bleed solenoid
Torque converter clutch:  258mm
Converter size:  246mm (reference) (diameter of torque converter turbine)
Fluid type: DEXRON® VI
Transmission weight:  wet: 104 kg 
Fluid capacity (approximate):  9.0L
Bottom pan removal: NA
Pressure taps available: line pressure
Transfer design: three-axis design
Assembly sites: Warren, Mich.
Applications: Saturn Outlook



2007 Model Year Summary

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

GMC Acadia
(Dual Exhaust)                                 6T75

Saturn Outlook
(Dual Exhaust)                                 6T75

Saturn Outlook (Single Exhaust)     6T75

Buick Enclave                                     6T75

Pontiac G6 (2DrNB)                         6T70

Pontiac G6 (4DrNB)                          6T70

 Saturn Aura                                         6T70


● 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






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).



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.



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).



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.



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.



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.



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.



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.



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.



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.



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.




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.




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.


MORE !!!!!!!!!!!!!!!!!!!!!!!



FOR RELEASE: 2006-06-01


Innovative, Compact Six-Speed FWD and AWD Transmission Handles High Torque and Boasts Smooth Shifting, Aids Fuel Efficiency



  • On-axis design enables spacious packaging
  • Advanced clutch-to-clutch shift operation
  • Wide 6.04:1 overall ratio spread
  • Co-developed by GM and Ford Motor Co.
  • Engine torque capacity from 280 lb.-ft. to 300 lb.-ft.
  • Shift speeds up to 7000 rpm
  • Calibrated for quick launch and fuel-efficient cruising
  • Built at GM Powertrain's transmission plant in Warren, Mich.

WARREN, Mich. - The new Hydra-Matic 6T70 and 6T75 front- and all-wheel drive six-speed automatic transmissions will debut in several GM models in 2007. The Saturn Aura and Pontiac G6 will offer the 6T70 as an option, and the 6T75, which is rated for higher torque capacity, will be standard in the Saturn Outlook, GMC Acadia and Buick Enclave crossovers.

The 6T70/75's clutch-to-clutch operation and 6.04:1 overall ratio help the transmissions deliver both performance and fuel economy, enabling up to 7 percent improved performance and up to 4 percent improved fuel economy when compared with current front-wheel drive four-speed automatics. Both transmissions use a very high numerical 4.48:1 first gear, which helps deliver exceptional launch feel, and a 0.74:1 overdrive sixth gear, which reduces engine rpms at high speeds, thereby reducing engine noise and vibrations. Fifth gear is 1.1 direct drive.

The final drive ratios can be tailored to each vehicle's performance requirements. For the Saturn Outlook, the final drive ratio is 3.16:1, while the Aura sedan uses a taller 2.77:1 ratio.

The 6T70 is rated for engines up to 315 horsepower and 280 lb.-ft. of torque, and with its larger transfer gears, a five-pinion input carrier and beefier structural ribbing on its aluminum case, the 6T75 can handle engines up to 315 horsepower and 300 lb.-ft. of torque.

The co-development by GM and Ford meant that many common components of the transmission are shared, along with the on-axis design; but the controls, calibrations and operation of the transmission are unique to each company. Costs and development time were reduced in some areas by 50 percent because of the co-development process.

"The additional gear states are almost like having two transmissions in one," said Bob Vargo, assistant chief engineer for the new transaxle. "The low first gear provides tremendous off-the-line acceleration, but the transmission is able to use the middle gears to evenly distribute the torque and offers an overdrive sixth gear that helps deliver great fuel economy."

Because there are six gears instead of four, the difference between ratios is less than in a four-speed automatic, giving the vehicle more options for using the best ratio for speed and load conditions. For example, with the transmission in an optimum ratio on a hill, the engine will not need to downshift or upshift unnecessarily. Driver Shift Control further reduces shift events by allowing the driver to select a desired gear for certain road conditions, such as steep and long hills, and automatic grade braking for descending hills. Automatic grade braking reduces brake pedal usage by calculating the rate of acceleration while descending a hill, and retaining a lower gear in the transmission.

The electronic controls are designed so that the shift feel is calibrated specifically to either the new midsize sedans or the new midsize crossover vehicles through the timing of the shifts and torque converter lockup speeds. The space-saving hyper-elliptical, narrow section torque converter uses a single-plate lockup clutch that employs GM's proprietary ECCC (electronic converter clutch control) to dampen driveline vibrations.

The Hydra-Matic 6T70/75's highlights:

  • Dimensions of 357 mm in length and 197 mm in width approach those of some manual transmissions, and are among the most compact for a six-speed automatic, and for front- and all-wheel drive vehicles with transverse-mounted powertrains
  • Clutch-to-clutch shift operation for all shifts except 1-2 reduces mechanical complexity and mass, and is calibrated for smooth shift feel
  • Integrated transmission electro-hydraulic control module (TEHCM) with driver shift control (DSC), auto grade braking for consistent speed in hilly terrain and while towing or fully loaded
  • Internal control module reduces powertrain complexity
  • Heat-treated gears are honed for a more precise fit, reducing noise, vibration and harshness
  • Hyper-elliptical, narrow-section torque converter enhances packaging and maintains efficiency
  • Reduced number of seals for stronger input shaft design
  • Adjustable capacity vane-type fluid pump enhances fuel economy

Although used in some low-volume, high-performance sports cars and luxury sedans, six-speed transmissions are rare in midsize sedans and most high-volume midsize SUVs. GM and Ford Motor Co. recognized a need for a transmission that could accommodate increased powertrain performance while delivering excellent fuel economy. The compact size and reduced complexity afforded by the clutch-to-clutch, on-axis design allowed engineers to provide improved performance and economy with six forward speeds.

With its wide ratio spread and capacity for high-torque engines, the 6T70/75 has the capability to transfer more torque to the drive wheels, particularly in the all-wheel drive Outlook, Acadia and Enclave. It also helps vehicles to feel livelier at lower speeds for a given engine, particularly at launch or when accelerating from a stoplight.

The 6T70/75's advanced clutch-to-clutch operation is designed for smooth shift feel and packaging efficiency. All shifts except 1 (the transmission "freewheels" in first) feature clutch-to-clutch operation. The sophisticated electronic controls allow timing the clutch-to-clutch engagements and disengagements so that the transfer of power from one gear to the next is transparent to the driver. The three conventional planetary gears, with three stationary clutches and two rotating clutches, can be packaged in a smaller space without additional freewheeling mechanisms. It's a simple, less complex design that enables the packaging of six gears in the space of a four-speed automatic.

A sophisticated transmission electro-hydraulic control module (TEHCM) is mounted inside the 6T70/75, reducing vehicle complexity. Similar to the control system used in the Hydra-Matic six-speed rear-wheel drive transmissions, the TEHCM offers improved quality through its hard-wired connections and pre-calibration during the controller's manufacture.

The unit is located entirely within the transmission and operates while bathed in transmission fluid. Locating the controller internally facilitates the modular design and assembly strategy while also shielding the unit from the outside environment. Temperatures are consistent inside the transmission.

GM's proprietary model-based controls strategy reaches a greater level of sophistication in the new transverse six-speed transmission family, said Vargo. The 32-bit system incorporates three levels of "learning" that actually allow the components to adapt to one another.

It is not uncommon to have a transmission-control module that adapts to the specific transmission with which it is mated; however, the 6T70/75 accomplishes this with two steps: when the control module assembly is manufactured, and when it is installed inside the transmission.

As with other GM transmissions, the programming optimizes performance characteristics according to a variety of vehicle inputs. Finally, the new six-speed automatic adds another level of adaptability. Certain components within the major subsystems that make up the transmission "learn" from one another - via the controller software - in a unique form of self-adaptation that maximizes the interface of all the "networked" components. This procedure takes place as the transmission "tests" itself and the interaction of its internal components before it is shipped from the assembly plant.

The TEHCM also enables performance-oriented and driver-controllable shift features, including driver shift control "tap shift" and auto-grade braking for the midsize SUV and Performance Algorithm Shifting (PAS) for the midsize sedan. PAS recognizes a driver's particular style of throttle and brake application and essentially "reads his or her mind" and predicts which gear will be most advantageous for performance driving or economical cruising.

# # #


  2007 6T70 (MH2) 2007 6T75 (MH6 MY9)
Type: six-speed front-wheel drive, electronically controlled, automatic overdrive transaxle with an electronically controlled torque converter clutch six-speed front-wheel drive & AWD, electronically controlled, automatic overdrive transaxle with an electronically controlled torque converter clutch
Engine range: 4.0L 4.6L
Maximum engine torque (lb-ft / Nm) : 280 / 380 301 / 406
Maximum gearbox torque (lb-ft / Nm): 462 / 515 463 / 515
Gear ratios:    
First 4.48 4.48
Second 2.87 2.87
Third: 1.88 1.88
Fourth: 1.47 1.47
Fifth 1.00 1.00
Sixth 0.74 0.74
Reverse: 2.88 2.88
Final drive ratio: 2.77  3.16:1
Maximum shift speed: 1-2: 6800 rpm 1-2: 6800 rpm
2-3: 6800 rpm 2-3: 6800 rpm
3-4: 6800 rpm 3-4: 6800 rpm
Maximum validated gross vehicle weight lbs/ kg: 4850 / 2205 6384 / 2901
Shifter positions: P, R, N, M P, R, N, M
Case material: die-cast aluminum die-cast aluminum
Shift pattern: 4 VBS solenoids 4 VBS solenoids
Shift quality: variable bleed solenoid variable bleed solenoid
Torque converter clutch: 258 mm 258 mm
Converter size: 246 mm (reference) (diameter of torque converter turbine) 246 mm (reference) (diameter of torque converter turbine)
Transmission weight: wet: 102 kg wet: 104 kg
Fluid capacity (approximate): 9.0 L 9.0 L
Bottom pan removal: NA NA
Pressure taps available: line pressure line pressure
Transfer design: three-axis design three-axis design
Assembly sites: Warren, Mich. Warren, Mich.
Applications: Saturn Aura, Pontiac G6 Saturn Outlook, GMC Acadia, Buick Enclave


Susan Garavaglia
GM Powertrain Communications
Phone: 248-857-4368
Mobile: 313-378-9335
E-mail: susan.garavaglia@gm.com