Subaru XT 1988 Service Manual page 541

AUTOMATIC TRANSMISSION AND DIFFERENTIAL
3-2
Name
Function
4-2 relay valve Memorizes the 4th speed position, and prevents gear sh!fting from 4th to 3rd to
2nd speeds due to combined operation of the 4-2 sequence valve, shift valve A and
shift valve B when shifting down from 4th to 2nd speeds.
4-2 sequence valve
Inhibits release of band servo operating pressure acting at 4th speed until the high
clutch operating pressure and band servo release pressure (same hydraulic circuit)
are drained when shifting down from 4th speed to 2nd speed.
Servo charger valve
The 2nd speed band servo actuating hydraulic circuit has an accumulator and
one-way orifice for relieving shift shock when shifting from 1 st speed to 2nd speed.
The servo charger valve is installed to ensure sufficient oil flow when shifting down
from 4th to 2nd speed, or from 3rd to 2nd speed. It operates at 3rd or higher
speeds and supplies the 2nd speed band servo actuating pressure by bypassing the
one-way orifice.
3-2 timing valve
When shifting down from 0 3rd to 0 2nd speed, the timing valve retards the release
of band-servo pressure and creates a temporary neutral condition so that vehicle
speed can be changed smoothly.
"1" Reducing valve Reduces the low & reverse brake operating pressure so as to relieve engine braking
shock when changing from "2" range 2nd speed to 1 st speed.
Overrunning clutch reducing Reduces the operating pressure applied to the overrunning clutch so as to relieve
valve engine braking shock. In the "2" and "3" ranges, line pressure is applied to the
valve to raise the pressure adjusting point, thereby increasing engine braking
capacity.
Torque converter regulator valve Prevents excessive rise of torque converter pressure.
•
Lock-up control valve Controls the operation of the lock-up function.
•
Lock-up control plug Smoothes the transition between the lock-up state and release state.
•
Lock-up control sleeve
Shuttle shift valve 0 Changes the oil passage so that output pressure to the duty solenoid B (lock-up)
will be applied to the lock-up valve in the "0" range 2nd, 3rd, or 4th speed.
(Lock-up at 1 st speed is inhibited.)
at 1st speed is inhibited.)
*
Lock-up control is not actuated if the lock-up solenoid does not generate output
pressure when signaled from the control unit, even if the vehicle is in the "0"
range 2nd, 3rd, or 4th speeds.
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