Description And Operation: Description
The 948TE 9-speed automatic transmission with electronic shift control has an integrated Transmission Control Module (TCM) mounted to the transmission case. All functions are completely electronic.
The 948TE 9-speed automatic transmission includes the following features:
- nine forward speeds.
- lock-up torque converter.
- filled-for-life transmission fluid, no dipstick required.
| A | A Clutch Dog Clutch |
| B | B Clutch |
| C | C Clutch |
| D | D Clutch |
| E | E Clutch |
| F | F Clutch Dog Clutch |
| 1 | Transfer Gear Bearings |
| 2 | Differential Bearings |
Torque Converter
The torque converter includes:
- unique housing shape to incorporate multi-surface (2) Torque Converter Clutch (TCC).
- a multi-surface torque converter clutch system improves durability and provides increased torque capacity at reduced apply pressures.
- a TCC which can engage in any of the nine forward gears.
- a turbine dampening system suppresses torsional vibrations from the engine to ensure optimal shift quality and reduce Noise, Vibration, And Harshness (NVH) concerns.
The torque converter is attached to the engine drive plate with three sets of two bolts.
Transmission Fluid Pump
The transmission fluid pump:
- is located in the transmission fluid pump housing inside the bell housing of the transmission case.
- is driven by the torque converter using a chain and sprockets.
- is a double-stroke vane pump.
- has dual chambers with two inlet and two outlet ports which assists with fluid volume.
- filter is mounted directly to the transmission fluid pump and is not serviced through the transmission fluid pan. It is only replaced as part of a major transmission repair.
Differential and Ring Gear
The differential and ring gear assembly consists of:
- a ring gear.
- a preload shim.
- a case side support bearing.
- a bellhousing side support bearing.
The ring gear (1) is bolted to the differential housing. Opposing tapered roller bearings (3, 4) support the housing. A shim (2) located under the case side bearing race provides bearing preload adjustment.
Transmission Fluid Pressure Sensor
The pressure sensor (1), mounted to the valve body, monitors the dog clutch hydraulic exhaust circuit. The sensor reacts to the pressure changes that occur during dog clutch engagement and disengagement.
The transmission fluid pressure sensor output is monitored by the TCM for control and diagnostics. The TCM can use the pressure value provided by this sensor to compute system pressure and clutch apply pressure using a proprietary software algorithm.
Transmission Fluid Temperature Sensor
The transmission fluid temperature sensor (1) is part of the transmission pass-through wiring harness. The TCM uses the sensor to monitor transmission oil temperature.
Speed Sensors
The input and output speed sensors (1) are part of a single assembly located under the valve body. The speed sensors are active digital sensors. The input speed sensor uses the E-clutch housing as a reluctor, the output speed sensor uses the transfer gear.
Transmission Range Sensor
The TRS (1) is a non-contact Hall-effect sensor. It is a five wire sensor with circuits for Park, reverse, Neutral and Drive.
Valve Body
The valve body assembly contains all the sensors and solenoids which the Transmission Control Module (TCM) strategy requires for operation inside the transmission.
Transmission Control Module (TCM)
The TCM is mounted on the outside of the transmission case, over the differential. The electronic control system consists of various components providing inputs to the TCM. The TCM monitors transmission sensors, shifter assembly, and bus messages to determine transmission shift strategy. After shift strategies are determined, the TCM controls the actuation of transmission solenoids, which controls the routing of hydraulic fluid within the transmission, by moving a sequence of four valves to make a shift occur. The system performs its functions based on continuous real-time sensor feedback information. In addition the TCM receives information from the rest of the vehicle over the Controller Area Network (CAN)-C bus. The CAN-C bus is a high-speed communication bus that allows real time control capability between various controllers. Most messages are sent every 20 milliseconds. This means critical information can be shared between the transmission, engine, and Automatic Braking System (ABS) controllers. The CAN-C bus is a two wire bus with a CAN-C Bus (+) circuit and a CAN-C Bus (-) circuit. These circuits are twisted pairs in the harness to reduce the potential of radio and noise interference. The transmission control system automatically adapts to changes in engine performance, vehicle speed, and transmission temperature variations to provide consistent shift quality. The control system ensures that clutch operation during up-shifting and downshifting is more responsive without increased harshness. The TCM activates the solenoid valves and moves valves in the valve body to achieve the necessary gear changes. The required pressure level is calculated from the load condition, engine speed, vehicle speed (from ABS module) and transmission oil temperature which are matched to the torque to be transmitted.