Subaru XT 1988 Service Manual page 570

3-2 AUTOMATIC TRANSMISSION AND DIFFERENTIAL
3-9 4WO Transfer Unit (Full-time 4WO)
1) OUTLINE
This 4WD transfer unit is an electronically controlled MP-T
type, full-time, four-wheel driving system which is unique to
SUBARU vehicles_ -It consists of a transfer hydraulic control
system composed of various sensors, a transmission control
unit, duty solenoids and a combination of hydraulic multi-
plate clutches.
Throttle opening sensor
The sensors and transmission control unit are also used in
common for gearshift control, lock-up control and hydraulic
pressure control.
Transmission control unit
Battery voltage
Input
interface
circuit
AID
converter
Circuit I
Fig. 82
I
ATF temperature sensor
Vehicle revolution sensor 1
(rear wheel rpm)
Vehicle revolution sensor 2
(front wheel rpm)
Range signal
Idle switch
1st hold switch
I I
Forced FWD switch
~-------'
I I
I I
I I
Input
interface
circuit
56
CPU
Memory
Constant voltage
source
I
~
L: __
~_~
Transfer
clutch
L3-659