Overdrive Range - First Gear

Overdrive Range - First Gear:

OVERDRIVE RANGE - FIRST GEAR

"A" SHIFT SOLENOID - ON
INPUT CLUTCH - APPLIED
FORWARD BAND - APPLIED
"B" SHIFT SOLENOID - ON
INPUT SPRAG - HOLDING
1/2 SUPPORT ROLLER CLUTCH - HOLDING

When the gear selector lever is moved to the 0VERDRIVE RANGE [D] the manual valve (404) moves and allows line pressure to fill the D-4 passage. D-4 pressure seats the #6 checkball (372) and sends fluid through the forward servo feed orifice into the servo apply passage. Servo apply fluid strokes the forward servo assembly (15-22) to apply the forward band (688). D-4 fluid also feeds the servo apply passage through the thermo element located on the spacer plate (370). D-4 fluid from the manual valve directs fluid to the following valves:
^ 1-2 accumulator valve (341) into the primary trim passage to the secondary.
^ 1-2 accumulator valve (347) and into the 1-2 accumulator passage.
^ 2-3 accumulator valve (343) and into the 2-3 accumulator passage.
^ 3-4 accumulator valve (350) and into the 3-4 accumulator passage.
^ 2-3 shift valve (357) and into the auxiliary input clutch feed passage.
^ 1-2 shift valve (318).

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

#6 Checkball (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 and thermo element on the spacer plate (370). When the manual valve (404) is moved from Drive to Park or Neutral, the checkball unseats to allow for a quick exhaust of servo apply fluid and release of the forward band assembly (688).

Forward Servo Boost Valve (367): 0pens under high line pressure (high throttle position) allowing D-4 fluid to by-pass the feed orifice and thermo element 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.

1-2 Accumulator Valve (341): Fed by D-4 pressure, it regulates primary trim fluid pressure to the secondary 1- 2 accumulator valve (347) in proportion to changes in modulator pressure.

Secondary 1-2 Accumulator Valve (347): Fed by primary trim fluid pressure, it regulates 1-2 accumulator pressure in proportion to modulator pressure. When primary trim reaches its breakpoint pressure, it is regulated lower by the secondary 1-2 accumulator valve.

2-3 Accumulator Valve (343): Fed by D-4 pressure, it regulates 2-3 accumulator pressure in proportion to modulator and "B" shift solenoid 0FF pressure.

3-4 Accumulator Valve (350): Fed by D-4 pressure, it regulates 3-4 accumulator pressure in proportion to modulator pressure.

2-3 Shift Valve (357): Allows D-4 pressure to enter the auxiliary input clutch feed passage.

1-2 Shift Valve (318): Held against spring pressure by "A" shift solenoid pressure, D-4 fluid stops at this valve until a 1-2 shift is made.