Copyright by Goodheart-Willcox Co., Inc.
212 Manual Drive Trains and Axles
Shift
rails
Shift fork Synchronizer
Shift knob
Gearshift lever
Pull rod
Interlock
sleeve
Boot
Rubber damper
Shifter ball
Shift rod
Sliding
ring
Figure 10-12. A typical gearshift lever. The boot keeps dirt and
water out of the passenger compartment. The sliding ring is
pulled up to move the lever to the reverse position, but not all
gearshift levers have such a feature. (Volvo)
Figure 10-11. A shift fork, such as the one shown here, fits into
the synchronizer outer sleeve. The fork can slide the sleeve
forward or backward as the sleeve rotates with the shaft.
(Chrysler)
Construction and operation of transaxle synchronizers is
essentially the same as that of the manual transmission.
(Refer to Chapter 8 for a detailed discussion of synchronizers.)
One difference between the synchronizers of transaxles
and those of manual transmissions is that transaxle
synchronizers may be located on both input and output
shafts. In the manual transmission, they are found only on
the output shaft.
Shift Forks
Shift forks, like the one shown in Figure 10-11, are
made to slip into a groove cut into the outer sleeve of a
synchronizer assembly. They are usually made from steel
or cast iron. Some shift forks have nylon inserts at the point
where they contact the outer sleeve to reduce wear and
noise.
Shift fork action in a manual transmission is identical
to that of shift forks in a rear-wheel drive manual transmis-
sion. The shift fork moves in a straight line to push the
synchronizer outer sleeve and blocking ring into engage-
ment with the mating gear. The design permits the synchro-
nizer assembly to continue to rotate as the outer sleeve is
moved. The shift fork, in conjunction with the synchronizer,
selects one gear when it is pushed forward and selects
another gear when it is pushed backward. The shift forks
are operated by the manual transaxle shift linkage.
Manual Transaxle Shift Linkage
The transaxle shift forks are operated by the vehicle
driver through a series of shafts, levers, links, and, some-
times, cables. There are many ways to transfer the force
applied to the gearshift lever to the transaxle transmission
gears. Most transaxle shift linkages are very simple, both in
construction and in operation. The gearshift lever and the
components that make up a manual transaxle shift linkage
are discussed in this section.
Gearshift lever
A typical gearshift lever is shown in Figure 10-12. The
gearshift lever may have a knob with a button, which is
depressed to obtain reverse. The lever may alternately have
a sliding ring, which is moved upward to obtain reverse.
Either mechanism prevents shifting into reverse while mov-
ing forward. Note that the lever extends downward through
a hole in the vehicle floor pan to the external shift linkage.
This hole is sealed by a flexible rubber boot. Sometimes,
two boots are used.
External shift linkage
The gearshift lever operates a shift mechanism under
the dust boot. Since the transaxle is placed far ahead of the
passenger compartment, external linkage must be used to
connect the shift mechanism and transmission internals.
External shift linkage consists of a series of levers and
rods or cables that connect the gearshift lever with the
transaxle internal shift linkage. A typical rod-and-lever
linkage system is shown in Figure 10-13. A typical cable
linkage system is shown in Figure 10-14. The cable linkage
system shown has two selector cables. Other systems may