Buick LeSabre 1965 Service Manual page 156

4 - 2 0 45000 SYNCHROMESH
CLUTCH, S-M TRANSMISSIONS
race is grooved for a snap ring
which retains the race in the rear
extension. The inner race is a
press fit on the mainshaft. The
bearing is prevented from moving
forward by the second speed gear
thrust washer, and retained at the
rear by a snap ring fitted into a
groove on the mainshaft.
The countergear is carried on
roller bearings at both ends, while
thrust is taken on washers lo-
cated between each end of the
gear and the case.
A hole in the hub of the counter-
gear permits lubricant to reach
the bearings and thrust washers.
The reverse idler gear is car-
ried on ball indented bronze bush-
ings. Forward thrust of the gear
is taken on a washer located be-
tween the front of the gear and
the case, while rearward thrust
is taken on a radial needle bear-
ing and a washer located between
the rear of the gear and the case.
The reverse idler gear shaft is
held in position by a pin passing
through the case into the rear
end of the shaft.
The second gear is mounted on
the mainshaft in such a position
that it is constantly in mesh with
the countergear. The gear is free
to rotate on the mainshaft except
when engaged by the synchro-
nizing assembly during second
speed operation.
The first-reverse sliding gear is
splined to the second-third speed
clutch so that it can be moved
forward to engage the countergear
for first speed or rearward to
engage the reverse idler for
reverse.
b. Gear Shifting and
Synchronization
1. Gear Shifting - Shifter forks
extending through the transmis-
sion side cover constitute the gear
change mechanism. The forward
lever moves the clutch sleeve
forward or rearward to provide
synchronized 2nd and 3rd speeds.
The rear lever moves the sliding
ring gear forward or rearward to
engage the countergear for 1st and
reverse speeds. A shift interlock
prevents both levers from moving
at the same time. One lever must
be in neutral position before the
other will function.
2. Synchronization
Gear shift synchronization is pro-
vided in 2nd and 3rd speeds by a
clutch sleeve with one synchro-
nizing ring at each end. The front
ring is positioned over the drive
splines of the main drive gear.
The rear ring is positioned over
the splines of the second speed
gear. 4 lugs on the rings fit into
slots in their respective gears,
causing the rings to rotate when
the gear rotates. This arrange-
ment allows the ring to slide on
the gear. An energizing spring,
positioned in a groove on the
gear, provides resistance to this
movement. As the clutch sleeve
is slid forward or rearward, the
beveled outer diameter of the ring
contacts the beveled inner diam-
eter of the clutch sleeve. The
ring, which is rotating at the
same speed as the gear, causes
the sleeve to rotate at the same
s p e e d the g e a r is rotating.
Further movement of the sleeve
forces the lugs of the synchro-
nizing ring over the energizing
spring on the gear. This resist-
ance to movement of the ring,
causes a more positive contact
between the sleeve and the ring.
Thus, the sleeve and ring rotate
at the same speed. Still further
movement of the sleeve allows
the internal drive splines of the
sleeve to mesh with the external
drive splines of the gear. This
provides a positive engagement
of the sleeve with the gear. Since
the clutch sleeve is splined to the
mainshaft, the gear is "locked"
to the mainshaft.
c. Speedometer Gears
The speedometer driving gear is
a press fit on the mainshaft. Nor-
mally, when changing rear axle
ratios it is unnecessary to change
the driving gear. However, with
certain ratios, changing the driv-
ing gear becomes necessary. See
Figure 4-27.
The driven gear and shaft is held
in the rear extension by a fitting,
lockplate, lock washer, and bolt.
An "O" ring provides a seal be-
tween the driven gear assembly
and the rear extension.
d. Power Flow Thru
Transmission
1. First Gear - M e c h a n i c a l
Action - The shifter fork slides
the ring gear into contact with
the middle gear on the counter-
gear. The countergear is in con-
stant mesh with the main drive
gear.
First Gear - P o w e r Flow -
Torque is i m p a r t e d to the
countergear by the main drive
gear. It is then transferred to the
ring gear on the clutch sleeve by
the middle gear on the counter-
gear. The ring gear is splined to
the clutch sleeve which, in turn,
is splined to the mainshaft.
2. Second Gear - M e c h a n i c a l
Action - The ring gear is moved
back to the neutral position and
the clutch sleeve is moved rear-
ward to engage the front part of
the second speed gear. The sec-
ond speed gear is in constant
m e s h with the rear of the
countergear.
Second Gear - Power Flow -
Torque imparted to the counter-
shaft by the main drive gear is
transmitted to the second speed
gear. The second speed gear,
now splined to the clutch sleeve,
transmits torque to the mainshaft
through the clutch sleeve.