Overdrive Range - First Gear

OVERDRIVE RANGE - FIRST GEAR
When the gear selector lever is moved to the overdrive (D) position from the neutral (N) position, the following changes occur to shift the transaxle into overdrive range - first gear.
Manual Valve: In the overdrive position the manual valve routes line pressure into the drive fluid circuit. Also, the manual valve blocks line pressure from entering the PRN fluid circuit and opens the PRN fluid circuit to exhaust.

Low and Reverse Band Releases
Lo and Reverse Servo: Lo band fluid pressure exhausts from the servo, thereby releasing the servo and the lo and reverse band.

Forward Clutch Applies
Forward Clutch: Drive fluid is orificed into the forward clutch fluid circuit. Forward clutch fluid pressure applies the forward clutch.
1-2 Shift Solenoid (1-2 SS): In first gear 1-2 SS remains energized by the Powertrain Control Module (PCM) and 1-2 signal fluid pressure acts on the 1-2 shift valve.
1-2 Shift Valve: 1-2 signal fluid pressure keeps the 1-2 shift valve in the downshifted position against spring force. Drive fluid is routed through the 1-2 shift valve.
Transmission Fluid Pressure (TFP): Drive fluid is routed to the TFP and the TFP signals the PCM that the transaxle is in the overdrive range.