The Hydraulic System
| 1. Transmission Control Module (TCM) | 5. Oil cooler |
| 2. Torque converter | 6. Oil pump |
| 3. Valves and solenoids | 7. Planetary train |
| 4. Clutches and brakes | 8. Oil sump |
The transmission's hydraulic system consists of oil pump, torque converter, hydraulic control system and oil cooler.
The solenoids, which control the hydraulic valves, are located in the gearbox control system, which is fitted at the front of the gearbox. The solenoids are activated by TCM (1). For information about TCM, see separate information.
The oil pump (6) supplies the hydraulics with oil and supplies other parts of the gearbox with oil for lubrication and cooling. Surplus oil is routed back to the oil sump (8).
The oil level is checked though a level pipe (the transmission does not have conventional oil dipstick). For information on how oil level is checked, see Information - Repair - Cleaning, checking and adjusting - Power transmission - Gearbox.
Shifting takes place by means of the oil pump building up hydraulic pressure. The hydraulic valves, which are each controlled by their own solenoids, send the hydraulic pressure to the relevant clutch, brake or lock-up depending on signals from TCM.
The transmission oil differs from conventional ATF oil properties. Always use transmission oil that is specified for this transmission. Otherwise the function of the transmission will be damaged.
Hydraulic pressure chamber
A = Piston's hydraulic pressure chamber
B = Counter acting hydraulic pressure chamber
When the rotation of the clutch increases, the centrifugal force affects the oil inside the clutch. The hydraulic pressure increases and the clutch engages. The centrifugal force means that a difference occurs in the rotation between the input and output shafts, which can mean a shift judder. To solve this, there is an extra pressure chamber opposite the piston's hydraulic pressure chamber. This extra pressure chamber means that the centrifugal force also works in the opposite direction and therefore affects the pressure from the piston's hydraulic pressure chamber. In addition, the clutch does not engage too soon.