TRANSMISSION—OVERDRIVE
25
in the kickdown circuit through the release of the spring
lever on the outer end of the solenoid. The circuits are now
in normal condition for continuing the overdrive operation.
In order to understand the overdrive control system, the
first thing to remember is that any time there is an open
switch in a circuit, that entire circuit is open and inactive.
When all three switches in the governor circuit are
closed. the relay coil is energized, closing the relay points.
This completes the solenoid circuit and energizes the
solenoid, which through the locking pawl, locks the sun
gear and places the overdrive in cruising gear. Also, any
time any one of the three governor circuit switches is open,
the relay coil is de-energized, the points open, and the
solenoid circuit is broken.
At Speeds Below 26 Miles Per Hour
With the cruising gear control forward at speeds below 26
miles per hour, every switch in the governor circuit is
closed except the governor switch. But this one open
switch is enough to keep the entire governor circuit and the
solenoid circuit open, and the solenoid remains de- ener-
gized.
At Speeds Above 26 Miles Per Hour
As the speed of car passes 26 miles per hour, the governor
points automatically close. This completes the governor
circuit, energizes the relay, and closes the relay points,
thus energizing the solenoid.
Then, with the momentary release of the accelerator
pedal, engine torque is released just long enough for the
solenoid pawl to move off the step of the balk ring and
engage the notch of the lock plate locking the sun gear.
This places the car in cruising gear.
Kickdown Operation
With the car in cruising gear at speeds above 26 miles per
hour, depressing the foot accelerator all the way to the
floor places the overdrive in overtake position.
The accelerator pedal now in the wide open position
breaks the governor circuit and completes the kickdown
circuit. The break in the governor circuit de- energizes the
solenoid. The closing of the kickdown circuit momentarily
"shorts out" the distributor (for approximately two crank-
shaft revolutions) releasing engine torque just long enough
for the solenoid pawl to disengage. The instant the sole-
noid disengages, the solenoid ground-out points automati-
cally open, restoring the distributor circuit. The car then
remains in direct gear as long as the engine is kept under a
pulling load.
DIAGNOSING OVERDRIVE TROUBLES
Since overdrive troubles may originate not only in the
mechanical operation of the unit but also in the electrical
circuit which controls that unit, the service man
should always check the control system before disassem-
bling the overdrive.
If the trouble is not found after a thorough inspection of
the control system, then the transmission and overdrive
should be removed for examination.
Unsatisfactory Overdrive Operation. Look for:
Burnt relay fuse in solenoid circuit.
Loose terminals on any of the connecting wires. Incor-
rect terminal locations of connecting wires. Circuits
grounded by water, dirt, or deformation. Defective
solenoid points.
Dirty or sticking relay contacts.
Insufficient travel or unsatisfactory contacts in the
kickdown switch. (Adjust or replace.)
Excessive end play in the governor shaft. Improper
adjustment of governor control springs. Burnt contact
points in governor.
Damage to cap and contacts.
Absence of rubber cover to exclude water and dirt.
Insufficient travel of shift rod. (Adjust control cable to
operating lever.)
CHECKING INOPERATIVE OVERDRIVE
Mechanical Checks
Determine if the overdrive control button is pushed for-
ward to the limit of travel.
Check to insure that the overdrive cable is adjusted to
move the overdrive lever firmly against the stop on the
overdrive housing in the engaged position.
Electrical Checks
With the ignition switch on, and the overdrive button
pushed forward, use a test wire or a 12-volt test light as
follows:
Check the 30 ampere fuse in the overdrive relay for live
circuits and clean contacts.
Connect test lead directly from the "B" terminal on the
voltage regulator to the terminal "SOL" on the overdrive
relay mounted on the front of the cowl. This will supply
current to the solenoid which should operate. If it does not,
check for a possible defective connecting wire or connec-
tion at the solenoid terminal before condemning the sole-
noid.
Ground the relay terminal "KD" or "C". If the relay is
functioning properly, the points of the relay will close and
the solenoid will operate.
Ground the overdrive relay terminal on the kickdown
switch. If all circuits are correct to this point, the solenoid
should operate.
With the kickdown switch governor terminal grounded,
push the plunger in. This breaks the circuit and the sole-
noid should release.
If the solenoid operates in the above tests, all circuits up
to this point are correct and further investigation must be
conducted underneath the car.
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