Innovative, Compact Six-Speed FWD and AWD Transmission Handles High Torque and Boasts Smooth Shifting, Aids Fuel Efficiency
2010 bell housing .... 6T75 Correct housing in the picture
Be careful with those two pictures! The 6T75 and 6T70 have two different bolt patterns. As I mentioned above, the 6T70 will bolt up to the LS4. The 6T75 is the better option due to its "rigidity," per se. It will not bolt up. There has been talk of pulling out all of the internals from the two and swapping them, but an adapter plate is the logical route.
-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.
Shift speeds up to 7000 rpm
Weight: 216 lbs (98kg)
Additional Information
Fluid type Dexron VI Fluid capacity: valve body cover removal: 5.3-7.4 qts (5-7 liters)
Fluid capacity; fluid change: 4.2-6.3 qts (4-6 liters)
Fluid capacity: rebuild: 7.4 9.5 qts (7-9 liters)
The vent for the transmission is incorporated into the dipstick.
EC3 246 mm. hyper-elliptical, furnace-brazed torque converter. Torque converter contains a lip seal that may be damaged if the converter is removed or installed in any position other than vertical. Special tools are available; J46409.
5 clutches (3 holding. 2 driving); clutch-to-clutch shifting
1 diode / ratchet type, one-way clutch
2 shift solenoids: (On/Off design): SS1.SS2
6 variable bleed solenoids: PCS1. PCS2, PCS3, PCS4. PCS5, TCC
A Bosch-built. 32-bit TCM (TEHCV1) mounted inside the transmission on the valve body (referred to as the control solenoid valve assembly). The TCM (TEIICM) incorporates solenoids, pressure switches, and TFTs. and is bolted to the valve body. A special, spring-loaded bracket is used to force the TCM against a heat sink on the valve body. Failure to install the bracket will cause the TCM to overheat and shut down.
No shift valves are used.
Unit uses only one accumulator (4th, 5th, 6th).
Compensator circuits are used to control clutch release.
Remote-mounted, off-axis, chain-driven, vane-type oil pump
Internal Mode Switch (IMS) equipped
Performance Algorithm Shilling (PAS) programming
Performance Algorithm Lift fool (PAL) programming
Sport mode and TAP shift equipped
Adaptive strategies with fast learn capabilities
Reverse lockout feature
Grade braking
All of the FWD/AWD applications use a lube trough to provide lubrication during towing (figure 2). Towing the vehicle with the rear wheels elevated will result in a lube failure due to oil draining out of the lube trough. FWD applications can be dingy-towed and dolly-towed. AWD applications can only be dingy-towed.
Customer Features
The 6T70/75 applications use a feature you may have seen on other GM 6-speed and 4-speed applications. The 6T70/75 use the tap shift feature that was first introduced in the 4T40E and 4T65E applications. The tap shift switch style and wiring configurations will vary with the vehicle.
While the commands for a tap up- or tap downshift will vary with application, the basic functions remain the same in all applications. Each system has built-in protection programming to prevent the transmission from downshifting at excessive RPM, which could damage the engine.
In addition, depending on the application, the engine is protected from excessive RPM if the customer locks the shifter in M or L ranges while failing to command an upshift. In this scenario, the unit will either force an upshift at high RPM or the engine will reach fuel cutoff mode. The tap feature can also be used to force the vehicle to start in 2nd or 3rd gear from a stop.
The Aura applications have the switches mounted as paddle-type controls on each side of the steering wheel (figure 3). To operate the paddle-type control, the customer pulls the switch toward him or her to force a downshift. Pushing the paddle will force the transmission to upshift. For tap shifting to function, the shift lever must be in the M range.
The G6 applications use a special gate, built into the shifter. The G6 shifter has an M position and another gate for tap shifting. To tap shift the G6 the customer simply moves the shift lever into the M position. From there, the customer can move the shifter toward the + or - gates to force a shift (figure 4).
The Outlook and Acadia use buttons mounted on the shift lever to trigger a tap shift. The shifter must be placed in the L position for tap shifts to function, from there, the customer simply presses the + or - buttons, located on the shifter, to force the shift (figure 5).
Tap Shift Electrical Operation
The tap switch assemblies contain two switch contacts and three fixed resistors. One resistor is used for diagnostic purposes while the other resistors signal the body control module (BCM) or the transmission control module (TCM) regarding the up- or downshift command, depending on the application.
The BCM or TCM monitors the voltage drop across the resistors to determine whether the customer is commanding an upshift or downshift. During a tap upshift, the voltage is dropped across a 1.5k-ohm resistor while a downshift command will force the voltage to drop across a 4.42k-ohm resistor (figures 6 and 7).
Shift Interlock System
Like other GM vehicles, the 6T70/75 applications use a Brake/ Transmission Shift Interlock (BTSI) system. A solenoid controls the transmission manual linkage.
To move the selector out of park, the driver must step on the brake pedal. The BCM monitors the brake switch input. When the brake is applied, the shift selector lever will be allowed to move out of the park position (figure
.
Fluid Level and Filter Service
Fluid level is checked with a dipstick on the 6T70/75. As with other GM 6-speed models, Dexron VI is the required fluid.
Fluid level is very sensitive on these units, so be sure to have the fluid at the proper temperature (180°-200°F; 82°-93°C).
The filter isn’t designed to be serviced during a fluid change. Unlike other applications, the 6T70/75 filter is sandwiched between the case halves so it isn’t easily accessed (figure 9). Fluid change intervals are 100.000 miles for normal service and 50,000 miles for severe-duty service.
The manufacturers are sure to expand the use of the 6T70 and 6T75 in the years to come. In the next segment, we’ll look at how the electronics systems operate in these units. Until then, remember: “Life is like riding a bicycle: you don’t fall off until you stop pedaling.”
