the solenoid when it is de-energized. Spring pressure pushes the 1-2 shift valve to the
right and allows D4 oil to pass through the valve and applies the 2-4 band servo. This oil
pressure, called 2
nd
oil, applies the band and shifts the transmission into second gear.
The number 8 check ball is used to restrict 2
nd
oil pressure to the servo and cushions
the shift. Pressure is also now available at the 3-2 downshift valve.
2.4.5 Drive, Third Gear
The 2-3 shift solenoid is a normally open solenoid, and oil exits through the valve when
it is de-energized. AFL oil pushes the 2-3 shift valve and 2-3 shuttle valve to the right.
2
nd
oil can now pass through the 2-3 shift valve.This oil is now called 3-4 SIG oil after it
passes through the 2-3 shift valve. In addition to applying and releasing holding
members, 3-4 SIG oil goes to the 3-2 downshift valve, 3-2 control valve, and 3-4 shift
valve for later use.
To apply the clutch, the 3-4 SIG oil passes through a check ball and orifice number 4.
The number 4 check ball and orifice restricts oil flow to the clutch piston to cushion the
shift.This oil is now named 3-4 CL (CL is for clutch) oil after it passes through the
number 4 check ball orifice. 3-4 CL oil is also sent to the 3-2 downshift valve and the 3-2
control vavle for use during 3-2 downshifts.
With the 3-4 clutch applied by 3-4 CL oil and band released by 3
rd
ACC oil, the
transmission is now in third gear.
2.4.6 ve, Fourth Gear
When enough speed is attained and other sensor inputs are correct, the ECM decides
that the transmission should be shifted into fourth gear. The ECM energizes the 1-2 shift
solenoid, sealing the exhaust passage in the solenoid. The 2-3 shift solenoid remains
de-energized.
With the 1-2 shift solenoiod back on, AFL oil pressure can build up on the right side of
the 1-2 shift valve through the orifice above the valve. Once through the orifice, the oil is
renamed SIG A oil.
The extra oil supplied by the 2-3 shuttle valve assits the spring and keeps the 1-2 shift
valve from moving. The AFL oil, renamed the SIG A oil, builds up to its full value and
moves the 3-4 shift valve.
With the 3-4 oil shift valve in the upshifted position, 3-4 SIG oil, renamed 4
th
SIG oil in
this circuit only, pushes the 3-4 relay and 4-3 sequence valves to the right. This allows
2
nd
oil to charge the 3-4 circuit that sends oil to the outer side of the servo. The outer
side of the servo is an apply area that helps the 2
nd
clutch oil overcome release oil and
spring pressure and reapply the band. Some 3-4 SIG oil is diverted to the 3-4
accumulator to improve shift feel. This is renamed 3-4 ACC oil.
2.5.0 Automatic Transmission Service
Automatic transmission service can be easily divided into the following three parts:
preventive maintenance, troubleshooting, and major overhaul. Before you perform any
maintenance or repairs on an automatic transmission, consult the maintenance manual
for instructions and proper specifications
.
NAVEDTRA 14050A
7-14