Chevrolet 10 Series 1968, Service Manual

Page: 206 / 713

REAR SUSPENSION AND DRIVE LINE 4-37
^ AXLE
\ L O
AXLE
Fig. 74—E le ctric Shift Control Switch
Should a short circuit occur the breaker will intermit­
tently de-energize the circuit until the trouble has been
corrected.
Three wires in the shift main harness (fig. 73) are
connected to the control switch. The red wire connects
the battery (thru the ignition switch and circuit breaker)
to the control switch. The white wire connects the con­
trol switch (thru the automatic switch) to one field of the
axle shift unit motor. The black lead connects the con­
trol switch (thru the automatic switch) to the other field
of the axle shift unit motor and also connects the speed­
ometer adapter.
Fig. 76—Shift Unit in High Range Position
Operation
The operation of the units in each speed range is ex­
plained in the following paragraphs.
High Speed Range
When the control switch operating arm is moved to the
up (HI) position, current is supplied to one field of the
motor in the axle shift unit. This current turns the ar­
mature and the drive screw in a clockwise direction and
moves the nut toward the bottom of the screw (fig. 76).
When the nut has traveled far enough to wind the
spring, a contact bumper on the nut breaks an electrical
connection on the automatic switch which de-energizes
the motor and stops armature rotation. The nut is held
at the end of its travel on the screw by a detent spring on
the shifting housing front cover.
As the nut moves downward, the spring winding lever,
Fig. 75—E le c tric Shift Unit Mounted F ig . 77—Sh ift Unit in Low Range Position
CHEVROLET TRUCK SERVICE MANUAL