Transmission System Description and Operation: Mechanical: Notes
The main mechanical components of the AF40-6 automatic transmission:
- Torque converter with lock-up clutch
- 2 planetary gear units, of which the rear is double
- 3 disc clutches
- 1 band type brake
- 1 multi-disc brake
- 1 free wheel
- Final drive with differential
| Callout | Component | Function |
|---|---|---|
| 1 | Torque converter housing | Torque converter housing protects the torque converter |
| 2 | Torque converter clutch | Disc clutch, also called lock up. Locks the impeller to the turbine using oil pressure. |
| 3 | Turbine | Coupled to transmission input shaft, drives the car when lock up is not active. |
| 4 | Impeller | Driven by engine, throws oil against the turbine. |
| 5 | Stator | Redirects the oil towards the impeller once it has left the turbine. Responsible for torque amplification. |
| 6 | Free wheel | The stator is mounted on the free wheel. This means the stator can rotate when the turbine has built up speed and so reduces energy loss. |
| 7 | Input shaft | The input shaft delivers the torque from the torque converter to the transmission. |
The torque converter is bolted to the engine flywheel (flexplate). The converter is filled with oil via pressure from the automatic transmission oil pump. This is itself a hydraulic transmission that amplifies the engine torque the more it slips. The greatest torque amplification is obtained when the engine stalls (car stationary and full throttle in Drive), as the engine torque is at a maximum while the transmission input shaft is stationary. There will not be any amplification if the engine speed is the same as the transmission input shaft speed.
The torque converter clutch (lock up) is activated at a steady speed when there is no need for torque amplification. The difference in speed between the engine and the transmission does give an amplification of torque even at steady speeds but also entails heat loss. These losses result in unnecessary fuel consumption.