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 (404)
Is moved by the gear selector lever and allows line pressure to enter the D-4 passage.

NO. 6 BALL CHECK VALVE (372)
Located in the valve body (300), blocks forward servo apply passage forcing D-4 pressure to the forward servo boost valve (367), the forward servo feed orifice on the spacer plate (370). When the manual valve (404) is moved from Drive to Park or Neutral, the ball check valve unseats to allow for a quick exhaust of servo apply fluid and release of the forward band assembly (688).

FORWARD SERVO BOOST VALVE (367)
Opens under high line pressure (high throttle position) allowing D-4 fluid to by-pass the feed orifices to enter the servo apply passage. This provides for a quick fill of the servo passage and quick apply of the forward band assembly (690) to prevent slippage during abusive shifts from Park or Neutral to Drive.

FORWARD SERVO ASSEMBLY (15-22)
Applies and holds the forward band (688) during all forward gear drive ranges.

FORWARD BAND ASSEMBLY (688)
Wraps around and holds the 1-2 support outer race (687) during all forward gear drive ranges.

TRANSMISSION FLUID PRESSURE (TFP) MANUAL VALVE POSITION SWITCH
D4 fluid is routed to the PSA and the PSA signals the PCM that the transaxle is in the Overdrive range.

1-2 SHIFT SOLENOID VALVE (315A)
Energized (ON) by the PCM, high pressure in the solenoid "A" fluid circuit holds the 1-2 shift valve in the downshifted position. Solenoid "A" fluid also is routed to the 3-4 shift valve, but is not effective.

2-3 SHIFT SOLENOID VALVE (315B)
Energized (ON) by the PCM, high pressure in the solenoid "B" fluid circuit holds the 2-3 and 3-4 shift valves in the downshifted position.

INPUT CLUTCH
Remains applied from Neutral to Drive and becomes effective as the forward band applies. The input sprag holds at this time.

1-2 SUPPORT ROLLER CLUTCH
The 1-2 support roller clutch holds when the forward band is applied.