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Brief description of AF30

Brief description of AF30

The AF30 is an electronically-controlled 4-speed automatic transmission with a Lock-up function.

AF30 consists mainly of a 4-speed planetary gear unit, a torque converter with Lock-up clutch, a hydraulic control system and an electronic control system.

The gearbox is controlled by a control module (TCM), which continuously processes information from its own sensors as well as from other control modules. On the basis of this processed information, it controls the transmission hydraulic system.

Compared with conventional hydraulically-controlled transmissions, the AF30 has the following advantages:


• Improved shifting performance and smoother shifting as torque is reduced when shifting takes place.

• Reduced mechanical stresses on the entire drive train due to torque limitation.

• Improved fuel economy through a consumption optimizing driving program and Lock Up in 3rd and 4th gear. Under extreme driving conditions when adaptive shifting programs are active, it is possible to drive with Lock Up in 2nd gear instead of 3rd gear without Lock Up. Improved shifting functions that are selected automatically if the temperature of the transmission fluid rises have been introduced. See Adaptive shifting programs.

• The possibility of selecting different driving programs: NORMAL, SPORT and WINTER.

• Self-diagnosis and storage of diagnostic trouble codes.


Compared with the earlier AF20/AF22 automatic transmissions, the AF30 incorporates the following modifications:




• The transmission casing, inner drive units and inboard drive-shaft universal joints are reinforced to withstand the higher torque developed (310 Nm).

• The TCM sends and receives information from the other control modules in the car through a bus communication system, see Bus communication .



P bus and I bus

See System overview . With the exception of the ABS and SRS, all control modules in the Saab 9-5 are connected to the bus.

The bus communication system consists of the Powertrain bus (P bus) and the Instrument bus (I bus). Both buses are connected to the main instrument unit (MIU). The two buses are electrically separate.

The data transfer rate of the P bus is ten times faster than that of the I bus.

All the information sent out from a control module is available to all other bus-connected control modules. The MIU sees to it that information which is available on one bus is also available on the other bus.

User recommendations

Selector lever position P

Position P must only be selected when the car is stationary. The selector lever and the transmission are both locked. The engine can be started.

Selector lever position R

Position R must only be selected when the car is stationary. This position cannot be selected without lifting the selector lever detent.

Wait a moment before depressing the accelerator to give the reverse gear time to engage properly.

Selector lever position N

With the selector lever in position N there is no connection between the engine and the transmission. The engine can be started. The handbrake should be applied to prevent the car from moving.

To avoid excessively high engine and transmission temperatures, N should be selected when the car is at a standstill for lengthier periods.

Selector lever position D

Position D is the normal driving position. After selecting this position, wait a moment before depressing the accelerator to give the gears time to engage properly. The transmission automatically shifts between gears 1 and 4. The shifting points depend on the position of the accelerator and the speed of the car.

Selector lever position 3

In this position, 4th gear is blocked. The car starts in 1st gear and then shifts automatically between gears 1 - 3.

Position 3 is recommended for driving on winding roads and in dense city traffic.

If the selector lever is moved from position D to position 3, the transmission will downshift to 3rd gear and more powerful engine braking will be obtained. The selector lever should not be moved to this position at speeds above 150 km/h.

Selector lever position 2

This position is preferable when driving in mountainous areas with a heavily laden car. Engine power is utilized more efficiently and engine braking is improved. the transmission shifts automatically between 1st and 2nd gears. Gear 3 and 4 are blocked. The selector lever should not be moved to this position at speeds above 150 km/h.

Selector lever position 1

Position 1 should be selected to provide stronger engine braking when descending extremely steep hills.

Moving the selector lever from position D to position 1 will result in immediate downshifting to 3rd gear. Downshifting to 2nd gear takes place at about 115 km/h and to 1st gear at about 60 km/h. Downshifting must not be performed manually at speeds above 150 km/h. With the selector lever in position 1, all other gears are blocked.

Towing

The following rules must be observed when towing a car that has automatic transmission:


1. The car must only be towed in the forward direction (front wheels leading).

2. The selector lever must be in position N.

3. Add 2 litres of fluid to the transmission over and above the normal amount. Use Texaco Texamatic DEXRON III (7045 EU, TL1863 US), mineral base oil.

4. National regulations governing towing speeds must be complied with.

The car must not be towed at speeds in excess of 50 km/h, even if the legal limit is higher. The car must not be towed further than 40-50 km. If it needs to be towed further than this, its front wheels must be raised off the ground.

5. When the car is ready to be used again the transmission fluid should be checked and, if necessary, drained to the prescribed level.

6. The engine cannot be started by pushing or towing the car.