AUTOMATIC TRANSMISSION – GM 5L40-E DESCRIPTION AND OPERATION 44-1-29 1 Line pressure from fluid pump 2 Bleed port 3 Clutch apply pressure from shift control valve 4 Damped clutch apply pressure from shift control valve 5 Spring 6 Piston The accumulators comprise a piston, a housing and a spring. The piston is sealed in the housing with O-ring seals and is subject to pressure applied by the spring. The housing has connection ports for fluid pump line pressure which is applied to the annulus of the piston and a port which receives clutch apply pressure from the shift valve and is applied to the full area of the piston. When line pressure from the pump is present, the piston is moved against the spring pressure. When a shift valve moves to supply clutch apply pressure, this is applied not only to the clutch piston but also to the accumulator piston. With the clutch apply pressure on the full area of the piston and with assistance from the spring, the piston is moved back against the line pressure. These opposing pressures create an action similar to a shock absorber. When the shift valve supplies clutch apply pressure, the pressure initially moves the clutch piston against the clutch piston spring and clutch plates. When the initial clearance between the plates is taken up, the clutch apply pressure builds rapidly. The clutch apply pressure is also applied to the full area of the accumulator piston and the rapid buildup of pressure moves the accumulator piston against the line pressure, assisted by the spring. The movement of the accumulator piston delays the buildup of pressure in the circuit and provides fora more gradual application of the clutch, resulting in a smoother clutch take-up. When the shift valve moves to cutoff the clutch apply pressure, the line pressure pushes the piston down the housing against the spring.