GMC PD-4103 Maintenance Manual page 202

Sec. 17
Page 182
GM COACH MAINTENANCE MANUAL
TRANSMISSION
11
1
2
3
4
6= 5
GEARSHIFT TOWER
Press Reverse
Button (See Text)
Reverse Shift Path
I
R2
3
4
GEARSHIFT DIAGRAM
1 Lever Ball Pin
2 Spring Seat Washer
3 Support Spring
4 Control Tower
5 Tower Base
6 Lubrication Line
7 Mounting Bolts
8 Poppet Ball
9 Poppet Spring
10 Dust Cover
11 Gearshift Lever
12 Shift Slides
13 Control Rods
14 Support Bracket
15 Bell Cranks
-·~-~Q
, 1 5 ~
---- 72'~lf5J~
(______--e
LINKAGE IN ENGINE COMPARTMENT
TP 4266
Figure 3-Transmission Controls and Linkage
tower and also where rear rods are connected
with levers at transmission.
When shift is made for any one of four for-
ward speeds (fig. 3) the movement of shift lever
is transmitted to transmission through various
rods, levers, and bell cranks.
Transmission control rods from shifting lever
to bulkhead are supported as illustrated in figure
3. First, second, and reverse gears are controlled
by the right-hand rod and third and fourth speed
by the left-hand rod. Rods pass through loom
packed with commercial graphite.
Rods and loom are supported in rubber grom-
mets in support brackets. Make all control rod
adjustments, with controls in neutral. Keep yoke
pins well lubricated -- refer to LUBRICATION
CHART in SECTION 13.
REVERSE SOLENOID AND RELAY
The reverse solenoid, mounted on the trans-
mission assembly is used to furnish pulling force
to move shift finger into engagement with reverse
speed shift fork.
Reverse solenoid has two coils, one known as
a pulling coil and the other referred to as holding
coil. Electrical circuit to solenoid is completed
by means of solenoid relay mounted on engine
compartment panel. Relay is in turn controlled
by reverse switch button at panel to the left of
driver. Relay control circuit is protected by a
circuit breaker located in circuit breaker panel
at left of driver.
When gearshift lever is in 1st speed position
the shift finger (19 fig. 7) is in line with notch in
reverse speed shift fork, hence pressing the re-
verse button at this time causes reverse solenoid
to operate, thereby moving finger into engagement
with reverse shift fork.
As gearshift lever is moved through reverse
shift path (fig. 3) the reverse idler drive and
driven gears are locked together by clutch and at
same time countershaft 1st speed gear is disen-
gaged from countershaft to become an idler gear
for reverse operation.
Both coils in reverse solenoid (fig. 5) are
energized to move the shift finger in transmission,
but as solenoid plunger reaches end of its travel
it strikes a pin which opens a set of points there-
by breaking circuit through pulling coil. The hold-
ing coil remains energized however and will hold
the solenoid plunger "in" as long as driver presses
the reverse switch button. Refer to Engine Control
and Generator wiring diagram in back of manual
for arrangement of wiring, junctions, and circuit
breaker.