Chamfered tooth ends of ring (external teeth) and sleeve (in-
ternal teeth)
Synchronizer ring and hub have three slots each, in which keys are
carried as backed by expanding springs, so that hub and its two
rings, one on each end, are capable of running together. Since
sleeve is engaged by its internal teeth with hub, as if the two were
splined together, sleeve too runs with hub and rings.
In meshing action, sleeve is pushed (by the shifter fork) to one side,
so that it slides axially on hub, pushing ring toward cone surface of
gear. This push is transmitted by three keys, which are lightly
gripped by sleeve.
By the friction between gear cone and ring cone (internal), ring be-
gins to rotate but is opposed by hub because of the keys. In other
words, the ring is at this time twisted, while the sleeve is advancing
further to push the ring fully against the gear cone. Since the ring
is unable to slide along any further, the sleeve lets go of the keys
and rides over to the ring. At this moment, the initial contact be-
tween the chamfered ends of teeth of ring and those of internal
teeth of sleeve occurs. This contact is such that the internal teeth
of sleeve align themselves to those of the ring.
When the sleeve advances and slides into ring, ring will be rotating
nearly with the speed of gear, so that sleeve is enabled smoothly
to slide over into clutch teeth of gear.
The initial contactor mesh between sleeve and ring is determined
by widths of key and slot or, to say the same thing, key clearance
in the slot, and is prescribed to extend at least a third (1/3) of the
chamfer.
With the synchronizer properly assembled on shaft, push in and
twist each synchronizer to see if the one-third mesh occurs or not;
if not, it means that the overall wear (which is the sum of the wears
of slots, keys and chamfered tooth ends) is excessive and, in such
a case, the entire synchronizer assembly must be replaced.
MANUAL TRANSMISSION (4-SPEED)
7A-13
Mesh of chamfered tooth ends of
synchronizer ring and sleeve
Contact extending about 1/3 of
chamfered face from apex
