Operation and Service of Aisin AF 17-4 Automatic Transmission
| Subject: | Operation and Service of Aisin® AF 17-4 Automatic Transmission |
| Models: | 2008 Saturn Astra |
| with Aisin® AF 17-4 Automatic Transmission (RPO MNF) |
Transmission Operation
The model year 2008 Saturn Astra will use the Aisin® AF 17-4 as the automatic transmission. The AF 17-4 automatic transmission is an electronically controlled 4-speed automatic transmission with lock-up features.
The AF 17-4’s main components are as follows:
| • | The torque converter with lock-up clutch |
| • | A 4-speed planetary gear unit |
| • | The hydraulic control system |
| • | The electronic control system |
The transmission control module (TCM) controls the operation of the clutches and brakes based on the shift pattern for the different driving modes: economy, power, and winter.
When the AF 17-4 shifts, the engine torque and the hydraulic pressure are controlled for smooth shifting in all driving situations. For further descriptions on how the AF 17-4 operates, refer to SI.
One unique operation of the AF 17-4 is called "neutral control". When a vehicle is stopped in "D" and the brakes applied, the AF 17-4 will go to the neutral condition, releasing the forward clutch (C1). With the decrease drag of the torque converter, it reduces the load on the engine and improves fuel economy.
After releasing the brake, the forward clutch (C1) will engage, the transmission will be in 1st gear and creep force will occur again. During the occurrence of "neutral control" the driver may sense a change in the engine operation. The driver should be informed that this is a normal operating characteristic of the vehicle.
Transmission Service
The AF 17-4 will have limited service. The following are the only items that can be serviced. These items can be replaced while the transmission is in the vehicle.
Part Number | Description |
|---|---|
72 | Park/Neutral Position Switch |
74 | Transmission Output Speed Sensor Assembly |
76 | Transmission Input Speed Sensor Assembly |
78 | Automatic Transmission Wiring Harness Assembly |
80 | Front Wheel Drive Shaft Oil Seal |
301 | Neutral Switching Solenoid Valve |
313 | 2-3 Shift Solenoid Valve Assembly |
316 | 1-2/3-4 Shift Solenoid Valve Assembly |
800 | Front Differential Carrier Seal Assembly |
819 | Transmission Fluid Drain Plug |
820 | Transmission Fluid Drain Plug Washer |
If the transmission requires removal to repair an internal condition, a new transmission can be ordered from GMSPO. A new transmission will be the replacement transmission for the first year of service. During the second year of service and beyond, an SRTA transmission will be available.
The AF 17-4 only uses T-IV fluid, GM P/N 88900925 (Canadian P/N 22689186). Any other type of automatic transmission fluid will cause shifting concerns and lower the life expectancy of the transmission.
