Clutches, Band Servos, and Accumulator

The front and rear clutch pistons, and both servo pistons, are moved hydraulically to engage the clutches and apply the bands. The pistons are released by spring tension when hydraulic pressure is released. On the 2-3 upshift, the kickdown servo piston is released by spring tension and hydraulic pressure.
The accumulator controls the hydraulic pressure on the apply-side of the kickdown servo during the 1-2 upshift; thereby cushioning the kickdown band application at any throttle position.