Automatic Transmission: Overview — Saab 9-5 II (2010-2012)

Transmission General Description

The AF 40-6 automatic gearbox is an electronic, 6-speed automatic gearbox with lock-up function. The gearbox is fitted directly against the engine and has a final drive gear 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 centre console. Manual up/downshifting is possible.

A special automatic transmission fluid must be used. The transmission does not have an oil dipstick. The plug has an extra center plug to check the level. It is connected to a rising tube that leads to the right level in the gearbox. 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 gearbox has planetary gears, disc clutches, brakes and torque converter with lock-up. The clutches and brakes are operated 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

Scheme 2: Overview of Clutches and Brakes

Output shaft gear
Intermediate Shaft
Location of oil pump
Input shaft
Differential Clutch
Rear planetary gear unit: (6a) Planetary gear (6b) Sun gear (6c) Ring gear
Front planetary gear: (7d) Planetary 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 (b1) Brake (b2) Brake (c1) Clutch (c2) Clutch (c3) Clutch (f1) Free wheel

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

Shifting	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

Scheme 3: Hydraulic

Torque Converter
Valve housing: (2a) Solenoid valve (2b) Linear solenoid (2c) Control valve
Clutch, brake
Oil Cooler
Oil Pump
Planetary gear
Oil Pressure
Gearbox oil, inlet
Gearbox 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 plug has an extra center plug to check the level. It is connected to a tube that leads to the right level in the gearbox. 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

(slc1) Solenoid Valve SLC1
(slc2) Solenoid Valve SLC2
(slc3) Solenoid Valve SLC3
(slb1) Solenoid Valve SLB1

Abbreviation	Abbreviation Expanded	Data
SLU	Lock up linear solenoid	Regulates the pressure to the torque converter clutch.
SLT	Throttle linear solenoid	Regulates the system pressure. Also used to slip in B2, which does not have its own solenoid. The system pressure is regulated so that is not higher than is needed for any friction element in order to reduce energy loss.
SLC1	Linear solenoid C1	Regulates pressure to clutch C1
SLC2	Linear solenoid C2	Regulates pressure to clutch C2
SLC3	Linear solenoid C3	Regulates pressure to clutch C3
SLB1	Linear solenoid B1	Regulates pressure to brake B1

Scheme 5

(slu) Solenoid Valve SLU
(slt) Solenoid Valve SLT

There are also 2 on/off-type solenoids. The following table shows these digital solenoids and their duties.

Abbreviation	Abbreviation Expanded	Data
S1	Solenoid 1	Pressure increase when slipping in C2.
S2	Solenoid 2	Pressurizing of brake B2 while engine braking in 1st gear.

Scheme 6

(s1) Solenoid Valve S1
(s2) Solenoid Valve S2

Scheme 7

Scheme 7: Cooling System

The automatic transmission (2) has an oil cooler integrated in the engine radiator (1) and constitutes one unit together with the transmission. Fluid is circulated by the transmission fluid pump and carried via hydraulic hoses (3) to the radiator and back to the transmission.

Scheme 8

Scheme 8: Control System

Circuit/System Description

The primary source of heat in the transmission is the torque converter. Hot oil exits the torque converter through the torque converter clutch (TCC) control valve and flows to the transmission cooler supply line. The supply line connects to the cooler, which is in the radiator. From the cooler, the oil returns through the oil cooler return line and enters the lubrication circuits. After lubricating the internal components, the oil returns to the oil pan. The transmission fluid temperature sensor is located in the control solenoid valve assembly.

Description and Operation

«TRANSMISSION INDICATORS AND MESSAGES»(ref-653642-S28726134132014090100000)
«TRANSMISSION COMPONENT AND SYSTEM DESCRIPTION»(ref-653642-S30187307232014090100000)
«TRANSMISSION OVERHEATS»(ref-653642-S16861106242014090100000)

The transmission control module (TCM) provides the engine control module (ECM) vehicle speed information through the high-speed communication on the controller area network (CAN). Vehicle speed is obtained through the alternating current (AC) which is created by the sensor for the rotation speed (OSS) of the gearbox output shaft when the output shaft is rotating. The ECM continuously monitors the vehicle speed signal provided by the TCM.