Transaxle Shifts

TRANSAXLE SHIFTS
Transaxle shifts are controlled by the manual valve and the PCM through the hydraulic solenoids.

The manual valve controls oil direction to provide 1st gear. When the transaxle has been shifted into D4 or D3, the 1st clutch is applied and the 1st sprag locks the 1st driven gear to the output shaft. The output shaft is driven counterclockwise by the 1st driven gear, causing the differential to turn clockwise in the forward direction. At the same time, 1st oil pressure is directed to the Forward/Reverse servo to assure the dog clutch is moved, locking 2nd driven gear to the output shaft.

At a predetermined point, based on vehicle speed, throttle position, and temperature, an upshift to 2nd will occur when the PCM opens the circuit to shift solenoid 2. When the circuit is opened, the solenoid is turned off electrically and turned on hydraulically, flowing oil to apply the 2nd/Reverse clutch. As the clutch applies, the ratio change causes the 1st gear sprag to overrun or freewheel and the shift to 2nd is complete.

When the transaxle shifts to 3rd, shift solenoid 3 is turned off applying oil pressure to the 3rd clutch. Shift solenoid 3 is then turned on, exhausting the 2nd/Reverse clutch as the 3rd clutch is applied. The 3rd to 4th shift is accomplished in the same manner.

The Torque Converter Clutch (TCC) is applied in 1st, 2nd, 3rd, and 4th gears. The speed at which the TCC will apply in 1st or 2nd is based on vehicle speed and tailored by throttle position, engine temperature, and transaxle temperature. Once applied, the TCC will stay applied until vehicle speed is low enough in 2nd gear for the TCC to release. The TCC will also release when the brake pedal is depressed in 2nd gear at low engine speeds or when the transaxle downshifts into 1st gear.

Reverse is controlled by the manual valve. When reverse is selected, the manual valve directs oil to the Forward/Reverse servo. The servo moves the Forward/Reverse dog clutch to the reverse position, releasing the 2nd driven gear and locking the reverse driven gear to the output shaft. As the dog clutch is engaged, the servo allows oil flow to shift solenoid 2. Shift solenoid 2 is turned off allowing the clutch to engage driving the 2nd/Reverse gear. The 2nd/Reverse gear turns the reverse idler gear driving the reverse driven gear clockwise. which in turn, provides reverse.