to the countershaft gears (fig. 4-13). The outer end of
the shaft is splined except the hub of the clutch disc.
The inner end has a machined gear that meshes with the
countershaft. A bearing in the transmission case
supports the input shaft in the case. Anytime the clutch
disc turns, the input shaft gear and gears on the
known as the cluster gear shaft, holds the countershaft
gear into mesh with the input shaft gear and other gears
in the transmission (fig. 4-14). It is located slightly
below and to one side of the clutch shaft. The
countershaft does not turn in the case. It is locked in
place by either a steel pin, force fit, or locknuts.
REVERSE IDLER SHAFT.The reverse idler
shaft is a short shaft that supports the reverse idle gear
(fig. 4-15). It mounts stationary in the transmission
case about halfway between the countershaft and
output shaft, allowing the reverse idle gear to mesh
with both shafts.
MAIN SHAFT.The main shaft, also called the
output shaft, holds the output gears and synchronizers
(fig. 4-16). The rear of the shaft extends to the rear of
the extension housing where it connects to the drive
shaft to turn the wheel of the vehicle. Gears on the shaft
are free to rotate, but the synchronizers are locked on
the shaft by splines. The synchronizers will only turn
when the shaft itself turns.
Transmission gears can be classified into four
groupsinput gear, countershaft gears, main shaft
gears, and the reverse idler gear. The input gear turns
Figure 4-13.Transmission input shaft and bearing.
Figure 4-14.Transmission countershaft assemblyexploded view.