Description & Operation: Introduction

The GF4A-EL is a 4-speed electronically controlled automatic transaxle. Six solenoids, located on valve body, control shift changes and shift feel. Solenoids are controlled by the Powertrain Control Module (PCM). PCM receives information from various input devices. PCM uses this information to control following solenoids:

• Shift solenoids "A", "B" and "C", control the line pressure applied to the 1-2, 2-3 and 3-4 shift valves.
• Torque Converter Clutch (TCC) control solenoid for torque converter clutch lock-up.
• 3-2 timing solenoid to reduce downshift shock.
• Pressure control solenoid regulates modifier pressure to control line pressure. The duty-cycle pressure control solenoid freely controls the ratio of ON time in one cycle from 0-100 percent. It repeats ON and OFF at a frequency of 31.25 Hz (0.032 second per cycle), and opens and closes the drain port to control modifier pressure at a specified level. Modifier pressure increases when the duty ratio (ratio of 31.25 Hz ON time) decreases. Modifier pressure decreases when the duty ratio increases. When the solenoid valve is OFF, hydraulic pressure applied to the valve is retained. The pressure applied to the valve overcomes the spring force and the valve moves to the left. When the solenoid valve is ON, pressure applied to the valve is drained and the valve moves to the right side by spring force. This valve switches the hydraulic pressure lines and controls the operation of the each component.