Q2-27. Which of the following components is NOT a
damaged propeller shaft, and damaged axles have been
common adjustment that can be made to an
eliminated.
automatic transmission?
excessive end play in the shafts cause noise operation
1.
The hydraulic control unit
of the transfer case. When you have decided that the
2.
The throttle linkage
trouble is within the transfer case, remove the unit from
3.
The control linkage
the vehicle for repairs.
4.
The bands
Make sure the transfer case is thoroughly cleaned
TRANSFER CASES
before disassembly of the unit begins. When the unit is
disassembled, clean each part with an approved
cleaning solvent. Inspection of the individual parts
LEARNING OBJECTIVES: Recognize the
should follow the same procedure as outlined for
purpose of transfer cases. Identify the
transmission. Avoid waste by reusing old parts that are
components of the transfer case. Identify
in good condition.
procedures for inspecting, checking, testing,
If you are not thoroughly familiar with a particular
and adjusting transfer cases.
make and model of transfer case, you should check the
manufacturer's repair manual to ensure that proper
Transfer cases are placed in the power trains of
adjustments and assembly procedures are followed.
vehicles driven by all wheels. Their purpose is to
Q2-28. During normal operation when both the front
provide the necessary offsets for additional propeller
and rear wheels are turning at the same
shaft connections to drive the wheels.
speed, the transfer case operates in what
Some transfer cases contain an overrunning sprag
specific manner?
unit (or units) on the front output shaft. (A sprag unit is
1. It applies torque to the front wheels only
a form of overrunning clutch; power can be transmitted
2. It applies torque to the rear wheels only
through it in one direction but not in the other.)
3. It applies torque to both sets of wheels at
On these units the transfer case is designed to drive
the same time
the front axle slightly slower than the rear axle. During
4. It applies torque to neither the front nor
normal operation when both front and rear wheels turn
the rear until there is a change of speed
at the same speed, only the rear wheels drive the
Q2-29. What is the first indication that a transfer
vehicle. However, if the rear wheels should lose
case is not operating properly?
traction and begin to slip, they tend to turn faster than
the front wheels. As this happens, the sprag unit
1.
The front wheels fail to turn
automatically engages so that the front wheels also
2.
The rear wheels fail to turn
drive the vehicle. The sprag unit simply provides an
3.
The vehicle will not move
automatic means of engaging the front wheels in drive
4.
The transfer case will produce unusual
whenever additional tractive effort is required. There
noises
are two types of spring unit transfers--a single and a
double. Essentially, both types work in the same
PROPELLER SHAFT ASSEMBLIES
manner.
The first indication of trouble within a transfer
LEARNING OBJECTIVES: Identify
case, as with other components of the power train, is
components of propeller shaft assemblies.
usually noisy operation. If an operator reports trouble,
Identify procedures for repairing or removing
make a visual inspection before removing the unit from
and replacing propeller shaft assemblies.
the vehicle. Check for such things as oil level, oil
leakage, and water in the oil.
The propeller shaft (drive shaft) assembly consists
Make sure the shift lever linkages are inspected. If
of a propeller shaft, a slip joint, and one or more
the shift lever linkages are bent or improperly
universal joints (fig. 2-81). The propeller shaft is a
lubricated, it is hard to shift the transfer case. In some
driving shaft that transmits the power from the
cases, this condition makes shifting impossible; make
transmission to the differential. Propeller shafts may
sure other possible troubles such as clutch slippage,
be solid or tubular. Tubular shafts are used when the
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