Transmission General Description
The AF 40-6 automatic transmission is an electronic 6-speed automatic transmission with lock-up. The transmission is mounted directly against the engine and has a final drive with integrated differential. The power unit is transverse mounted with all-wheel drive. Gear positions P-R-N-D are selected with the selector lever mounted in the center console. Manual up/downshifting is possible.
A special automatic transmission fluid must be used. The transmission does not have an oil dipstick. The drain plug has an extra central plug for checking the level. It is connected to a rising tube that reaches up to the correct level in the box. Fill the oil through the conventional oil filler plug until the level is correct and oil runs out of the check plug hole in the rising tube. Measure the temperature when checking the level. The temperature is read using a scan tool.
The AF 40-6 transmission has planetary gears, disc clutches, brakes and torque converter with lock-up. The clutches and brakes are applied hydraulically. The hydraulic system is controlled by the Transmission Control Module (TCM) with the help of 8 solenoids, 2 shaft speed sensors and one oil temperature sensor. TCM communicates on the high speed bus.
The TCM is mounted directly on top of the transmission and has one connector to the car's electrical system and one directly to the transmission. The gear position sensor is a Hall sensor and is integrated in the control module. The TCM is mounted so that the selector lever shaft goes through the control module. The selector lever position can be calibrated with the scan tool, there is no mechanical adjustment.
The TCM controls the transmission according to its programming, the information from its own sensors and from other control modules. The control module adapts its control of the solenoids to compensate for normal wear in the transmission. The TCM is SPS programmable.
Transmission Component and System Description
Gearbox functions can be divided into three parts
- Mechanical Components
- Hydraulic Components
- Control System
Operation of Clutches and Brakes
| Gear Position | C1 | C2 | C3 | B1 | B2 | B3 |
|---|---|---|---|---|---|---|
| P/N | ||||||
| R | X | X | ||||
| 1 | X | (X) | X | |||
| 2 | X | X | ||||
| 3 | X | X | ||||
| 4 | X | X | ||||
| 5 | X | X | ||||
| 6 | X | X | ||||
| (X) Only when engine braking. | ||||||
Scheme 2
- (B1) Brake
- (B2) Brake
- (C1) Clutch
- (C2) Clutch
- (C3) Clutch
- (F1) Free-wheel
- Output shaft gear
- Intermediate shaft
- Location of oil pump
- Input shaft
- Differential gear
- Rear planetary gear unit: (6a) Planet gear (6b) Sun gear (6c) Ring gear
- (7d) Planet gear (7e) Sun gear (7f) Ring gear (7g) Lock
- Planet carrier
- Front sun gear in rear planetary gear unit
- Rear sun gear
- Front planet carrier
- Front sun gear
Operation of Front and Rear Planetary Gear Units
| Gear | Front planetary gear | Rear planetary gear unit |
|---|---|---|
| R | The planet carrier rotates clockwise at reduced speed. | The front sun gear rotates clockwise (C3). The planet carrier is braked (B2). The ring gear rotates counterclockwise with reverse gear ratio. |
| 1 | The planet carrier rotates clockwise at reduced speed. | The rear sun gear rotates clockwise (C1). The planet carrier is braked by the free wheel (and by B2 when engine braking). The ring gear rotates clockwise with 1st gear ratio. |
| 2 | The planet carrier rotates clockwise at reduced speed. | The rear sun gear rotates clockwise (C1). The front sun gear is braked (B1). The ring gear rotates clockwise with 2nd gear ratio. |
| 3 | The planet carrier rotates clockwise at reduced speed. | The rear and front sun gears rotate clockwise (C1 and C3). The planetary gear unit is locked and rotates as one unit. The ring gear rotates clockwise with 3rd gear ratio. |
| 4 | The planet carrier rotates clockwise at reduced speed. | The rear sun gear and planet carrier rotate clockwise (C1 and C2). The ring gear rotates clockwise with 4th gear ratio. |
| 5 | The planet carrier rotates clockwise at reduced speed. | The front sun gear rotates clockwise (C3). The planet carrier rotates clockwise (C2). The ring gear rotates clockwise with 5th gear ratio. |
| 6 | Not used | The planet carrier rotates clockwise (C2). The front sun gear is braked (B1). The ring gear rotates clockwise with 6th gear ratio. |
Gear changing performance is controlled by the applied element. When changing gear, it is not possible to apply more than one friction element for consistent behavior. In the same way, it is not possible to release more than one friction element when changing gear. This means it is not possible to change from one gear to an optional gear. The following shows the normal gear changing sequence from standstill
| Gear Change | Applied Element |
|---|---|
| N to D (1) | Apply C1 |
| 1 to 2 | Apply B1 |
| 2 to 3 | Release B1, apply C3 |
| 3 to 4 | Release C3, apply C2 |
| 4 to 5 | Release C1, apply C3 |
| 5 to 6 | Release C3, apply B1 |
In this sequence you can clearly see that no more than 1 element is released or applied at one time. If you suddenly release the accelerator in 3rd gear after accelerating at full throttle, it is logical to change up to 6th gear.
Changing directly from 3 to 6, however, is not suitable because C1 and C3 must then be released and C2 and B1 applied. Changing 3 to 5 and 5 to 6 must be done instead. The need of these intermediate changes is especially noticeable during kickdown at various speeds. The permitted changing sequences are determined by a program in TCM.
The transmission is blocked mechanically in selector lever position P.
Scheme 3
- Torque converter
- Valve housing: (2a) Solenoid, solenoid valve (2b) Linear solenoid (2c) Control valve
- Clutch, brake
- Oil cooler
- Oil pump
- Planetary gear
- Oil pressure
- Transmission oil, inlet
- Transmission oil, return
- Operating pressure
- Lubrication
- Oil flow to pump
A special automatic transmission fluid must be used. The transmission does not have an oil dipstick. The drain plug has an extra central plug for checking the level. It is connected to a rising tube that reaches up to the correct level in the box. Fill the oil through the conventional filler plug until the level is correct and oil runs out of the level hole.
The temperature of the oil is important when checking the level. The temperature can be read with a scan tool.
All the friction elements are applied hydraulically. The hydraulic pressure is generated by a pump driven by the engine. The pump is mounted in the transmission behind the torque converter. The drive is direct from the torque converter.
Oil passes to the valve housing where the manual valve is integrated. The valve is affected by the gear selector wire, which in turn is operated by the selector lever. The valve has 3 positions, P/N, R and D/M. In position P/N, the oil will drain directly back to the transmission sump. In position R, the oil will pass directly to brake B2, which is used for reverse gear. In position D/M, oil will pass to the circuits used for the forward gears.
To control the flow of oil to and from the friction elements, 6 stepless (linear) solenoids are used. With them, TCM can regulate the pressure precisely. Each solenoid is connected to a mechanical control valve. They work as variable relay valves and are needed to control the relatively high flow of oil that is required. The solenoids do not possess the flow capacity needed to feed the oil directly to each friction element.
The table below shows the linear solenoids and their task.
Scheme 4
- On
- Off
- Ex
- (slc1) Solenoid valve SLC1
- (slc2) Solenoid valve SLC2
- (slc3) Solenoid valve SLC3
- (slb1) Solenoid valve SLB1