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A Different Way

The 4F27E transmission uses (2) ON/OFF solenoids and (3) PWM solenoids to produce each of the shifts
and converter clutch apply as the chart in figure 1reveals. The EPC solenoid is used to control line pressure
relative to engine torque. So far this sounds easy but from a strategy standpoint, it progressively moves
towards a “different way of doing things” when compared to what we are accustomed to. Lets start off on
familiar ground. Shift Solenoids A & B are the ON/OFF solenoids which when they are OFF, block fluid
from stroking valves while the C, D & E are the opposite. When they are
OFF they allow fluid to pass through the solenoid and stroke valves. OK, so far not so bad. Sounds a little
like the 41TE/42LE transmission with their Normally Applied and Normally Vented
solenoids.

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