8HP70 Automatic Transmission (Service Information): Operation: Notes
A unique transmission fluid has been developed for this transmission. This fluid is NOT compatible with ATF+4 or any other current FCA US LLC transmission fluid. For specifics about this unique fluid see CAPACITIES AND RECOMMENDED FLUIDS .
The 8HP70 is an electronic eight-speed automatic transmission. The Transmission Control Module Assembly (TCMA), which is integrated into the valve body, provides fully synchronized clutch-to-clutch shifting through four planetary gear sets. The TCMA includes a mounting plate that holds the Transmission Control Module (TCM) and a molded wiring harness for connection to various transmission sensors and solenoids. The valve body assembly contains all the sensors and solenoids required for operation, completely inside the transmission. Eight speeds allow the engine to maintain its optimal RPM range, increasing fuel economy and performance.
Transmission control is performed by the TCM based on hard-wired and CAN bus signals from sensors and modules. The TCM receives driveability data from the Powertrain Control Module (PCM) and other modules over the CAN-C bus. It also receives shift lever position information from the electronic shifter over a dedicated transmission CAN bus. The TCM processes this input data and controls operation of the torque converter clutch, park lock system, solenoid valves, and pressure regulating valve.
The input and output speed sensors are Hall-effect sensors that measure shaft rotational speed. The input speed sensor is located at the top, near the center, of the of the TCMA and reads input shaft speed from the magnetic ring on the P2 carrier. The output speed sensor is located at the back of the TCMA and reads output shaft speed from the P4 carrier
FILTER SERVICE The 8HP70 has a conventional fluid sump design, however, the filter is integrated into the oil pan resulting in a lower profile for improved vehicle packaging. The oil pan gasket is reusable providing it is not damaged during removal.
FLUID CHECK AND FILL A fluid fill tube and indicator are not provided. All work is performed under the vehicle while raised on a hoist. In the event of a transmission shift quality concern, a fluid leak, or in conjunction with a transmission repair, the transmission fluid level must be validated and topped off as necessary. The procedure involves the use of a scan tool to monitor transmission fluid temperature. Specific service procedures are necessary to check and fill the transmission with fluid. Refer to FLUID AND FILTER, STANDARD PROCEDURE .