2.1.1 eakage
Lubricant leakage in a transfer
case is a loss of lubricating fluid
from the housing, gaskets, or
seals. Leaks may be noticed as
oil drips on the pavement.
Always begin troubleshooting an
oil leak by making sure the leak
is from the transfer case. Engine
oil, transmission fluid, or power
steering fluid can be mistaken for
transfer case lubricant. As a
vehicle is driven, oil leaking from
the front components is
sometimes blown onto the rear
components. This makes it
difficult to determine the origin of
the leak.
One way to verify a transfer case
leak is to check the oil level in the
case. In most transfer cases, the
oil level is correct if the oil just
wets the bottom of the fill plug
threads (
Figure 8-22
). If the oil
Figure 8-22 - Checking oil level.
level is normal, the leak is probably from some other part of the vehicle. If the oil level is
low, there is generally a leak somewhere in the transfer case. If the oil level is too high,
overfilling may be the cause of the leak. Overfilling may cause oil to be forced out of a
seal or out through the case vents.
When looking for transfer case leak, remember that oil will drip downward and is often
blown to the rear of the vehicle. Look for the leaks from loose or broken bearing
retainers or from retainer gaskets. Check the seals in the area where the drive shaft
yokes enter the transfer case. Leaks may also originate from loose case housing bolts
and defective housing gaskets. Check for leaks from the drain and fill plugs, and from
bolts at the bottom of the transfer case. Some bolts must be installed with a thread
sealant to prevent leaks.
2.1.2 Engagement
When a transfer case fails to engage properly, no power will be transmitted to one or
both sets of wheels. However, a transfer case rarely fails to drive at least one set of
wheels. If the vehicle will not move in any transfer case mode, the problem is usually
caused by a defective transmission or by a binding axle. If the transfer case fails in only
one gear, the problem may be caused by defective internal parts or linkage.
Transfer case failure causing a no-drive condition in all gears is usually caused by
stripped gears or splines, a broken chain, a broken shaft, or a viscous coupling that has
lost its fluid. Generally, a transfer case must be removed from the vehicle to repair these
defects.
NAVEDTRA 14050A
8-31