4.1.1 TROUBLESHOOTING the PROPELLER SHAFT
ASSEMBLY
Propeller shafts or driveshafts have a simple function: to transmit drive torque from one
driveline component to another. This should be accomplished in a smooth, vibration-
free manner. In a heavy-duty truck, that means transmitting engine torque from the
output shaft of the transmission to a rear axle or to an auxiliary transmission.
Driveshafts also are used to connect forward and rear axles
Figure 8-42
shows the
driveshaft arrangement used in a tandem drive tractor equipped with an auxiliary
transmission.
Figure 8-42 - Driveshafts transmit torque between driveline components.
In most cases, a driveshaft is required to transfer torque at an angle to the centerlines of
the driveline components it connects to. Because the rear drive axle is part of the
suspension and not connected to the rigid frame rails of the vehicle, the driveshaft must
be capable of consistently changing angles as the rear suspension reacts to road or
terrain profile and load effect. In addition to being able to sustain constantly changing
angles, a driveshaft must be able to change in length when transmitting torque. When
the rear axle reacts to terrain or road surface changes, torque reactions, and braking
forces, it pivots both forward or backward, requiring a corresponding change in the
length of the driveshaft.
A driveshaft assembly is made up of the following:
1. Universal joints (U-joints)
2. Yokes
3. Slip splines
4. Propeller shafts
The propeller shafts have a tubular construction designed to sustain high torque loads
and be light in weight.
Figure 8-43
shows the components of a typical heavy-duty truck
driveshaft.
NAVEDTRA 14050A
8-49