Figure 5-32.Positive traction transfer case operation.
from the vehicle. Check for such things as oil level, oil
leakage, and water in the oil.
Make sure the shift lever linkages are not bent or
improperly, lubricated. This will make it hard to shift
or, in some cases, impossible to shift. Make sure other
possible troubles, such as clutch slippage, damaged
drive shaft, and damaged axles, have been eliminated.
Worn or broken gears, worn bearings, and
excessive end play in the shafts can cause noisy
operation. When transfer case service is required,
follow the procedures outlined in the service manual. It
will give directions for repairing the particular make
REVIEW 4 QUESTION
Q1. What is the gear ratio when a conventional
transfer case is in high range?
What component in a positive traction transfer
case provides power to the front wheels when the
rear wheel begins to slip?
Learning Objective: Explain the operation of a power
A power takeoff (PTO) is an attachment for
connecting the engine to power-driven auxiliary
equipment. It is attached to the transmission, auxiliary
transmission. or transfer case. A power takeoff
installed at the left side of a transmission is shown in
figure 5-33. It is used to drive a winch at the front of a
truck through a universal joint and drive shaft.
The simplest type of power takeoff is the
single-speed, single-gear shown in figure 5-34. This
unit may be bolted to an opening provided in the side of
a transmission, as shown in figure 5-35.
Shims or spacers are often used to ensure proper
contact is maintained between the teeth of the two
meshing units. The sliding gear of the PTO can then
mesh with, and be driven by, the countershaft gear of
the transmission or the auxiliary transmission when
engaged by the operator. The operator, by the use of a
control lever, can move the gear in and out of mesh
with the transmission gear. A spring-loaded ball
(poppet) holds the shifter shaft in position.
On some vehicles you will find PTOs with gear
arrangements that give you two speeds forward and
one in reverse. Several forward speeds and a reverse
gear are usually provided in a PTO unit used to operate
a winch or hoist. Operation of this type of PTO is
similar to that of the single-speed unit.
Faulty operation of a PTO is caused by damaged or
broken linkage. To prevent this, exercise care when
shifting. Trying to engage the unit with the
transmission gears turning can damage the teeth, and
rapid clutch engagement can break the housing. Rapid
shifting may bend or damage the linkage. Forcing the
control lever can bend or break the linkage.