MANUAL TRANSMISSION
POWERFLOW (
Understanding
the powerflow through a transmission helps the technician in diagnosing complaints
and determining the proper repairs to be done. The following illustrations show
the typical powerflow through a five speed transmission.
For
example, in first gear, power flows from the input shaft and main drive gear to
the counter shaft. First gear, on the counter shaft, drives first gear on the
output shaft. The first gear is locked to the synchronizer clutch hub
transmitting power to the output shaft.
On the
following three pages, in figures 3_14 through figure 3_19, the powerflow for
1st, 2nd, 3rd, 4th, 5th, and Reverse are highlighted and traced through a
transmission.
GEAR SHIFT MECHANISM
The gear
shift lever and internal linkage allow the transmission to be shifted through
the gears. The shift lever is mounted in the transmission extension housing and
pivots on a ball socket.
The shift
fork shaft connects the shift lever to the shift forks. A detent ball and
spring prevent the forks from moving on their own. The shift forks are used to
lock and unlock the synchronizer hub sleeve and are mounted on the shafts
either by bolts or roll pins.
The shift forks ride in the grooves of the
synchronizer hub sleeves. Shift forks contact the spinning synchronizer sleeve and
apply pressure to engage the gear. To reduce wear, the steel or aluminum forks
can have contact surfaces of hardened steel, bronze, low friction plastic, or a
nylon pad attached to the fork.
After the
sleeve has been positioned, there should be very little contact between the
fork and sleeve. The fork is properly positioned by the detent. The back taper
of the hub sleeve splines and spline gear, and gear inertia lock mechanism, keep
it in mesh during different driving conditions.
Holding a gear into mesh with the fork results
in rapid wear of the fork and hub sleeve groove. Wear at the shift lever ball
socket, shift fork shaft bushings, and shift fork contact surfaces may cause
the synchronizer sleeve to be improperly positioned, causing the sleeve to jump
out of gear.
Powerflow
Understanding powerflow through a transaxle helps in diagnosing complaints and determining the proper repairs. Power passes from the drive gear on the input shaft to the driven gear on the output shaft and through the synchronizer assemblies to the output shaft. For first gear, the smallest gear on the input shaft drives the largest gear on the output shaft, and for top gear, the largest gear on the input shaft drives the smallest gear on the output shaft.
Powerflow for reverse gear is similar to powerflow in a transmission. The reverse idler gear is shifted to mesh with the reverse gear on the input shaft and the sleeve of the 1_2 synchronizer assembly on the output shaft. The spur gear teeth for reverse are on the outer diameter of the synchronizer hub sleeve.
C & E Series Shift Fork Construction
Three fork shafts allow shifting into gears one through five and reverse. A shift head and shift fork is attached to each fork shaft. Shift forks are typically made from die cast aluminum and are attached to the shaft with a bolt.
Application
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