2.1.3 Abnormal Noises
Abnormal noises in the transfer case include whines and rumbles that occur during
operation. Other abnormal noises include grinding, knocking, popping, or snapping
sounds. Since the transfer case is mounted directly behind the transmission, it is easy
to mistake transmission or drive noise for transfer case noise. Always make sure the
noise is actually coming from the transfer case and not from some other part of the
vehicle.
Transfer case noises usually vary from driving conditions. If the transfer case is the part-
time type, road test the vehicle to determine the mode in which the problem occurs. If
the transfer case is the full-time type, the vehicle should be placed on a lift to listen to
for abnormal noises, such as grinding, knocking, or excessive whining. Remember that
normal drive train noises will seem louder when you are under the vehicle.
Typical causes of whining or rumbling noises in the transfer case include a low lubricant
level, worn or damaged input gear, worn or damaged driven gear, worn bearings, worn
planetary gears (where used), and damaged input or output shaft bearings. If the
speedometer gears are installed on the transfer case, check them for damage. A worn
drive chain can cause popping or snapping noises as the vehicle is accelerated.
Sometimes, the transfer case will be noisy because the front and rear axle ratios do not
match due to modifications. This can cause friction in the transfer case planetary gears
or coupling. To repair damaged or worn transfer case parts, the unit must be removed
and overhauled.
2.1.4 ear Disengagement
When the transfer case jumps out of gear, the shift mechanism will move into Neutral at
undesirable times. The first step in troubleshooting this type of problem is to determine
the gear in which the problem occurs. If the problem occurs in only one gear, the teeth
on that particular gear may be chipped or worn. Further, a blocking ring of a sliding
clutch of the affected gear may be worn.
2.1.5 Hard Shifting
In some cases, it may become difficult to change transfer case gears. Hard shifting may
be caused by a shift linkage that is bent or worn. In some cases, the linkage simply
needs lubrication.
Figure 8-23
shows shift linkage adjustment. If the linkage is okay, the
problem may be caused by bent or damaged shift forks inside the transfer case.
NAVEDTRA 14050A
8-32
