When filling the axle housing and planetary wheel ends, allow enough time for the oil to
flow through the components and find its natural level. When filling is completed, allow a
few minutes and then recheck the level again. The lubricant should be warm when
drained; this ensures that contaminants are suspended in the oil and get flushed out.
5.2.5 ow Lubricant Levels
Lubrication levels for vehicles and off-road equipment should be checked according to
the OEM service manual. Oil levels in drive axles must be checked properly; the oil level
must be even with the bottom of the oil filler plug hole. Oil replacement can be adjusted
according to your particular operations.
Remove the plug in the axle banjo housing; the oil should be even with the bottom of
the oil level plug hole (
Figure 8-108
). Note that if the pinion angle is more than 7
degrees, a different oil level is used. To properly check the oil levels in a differential
drive axle and the planetary wheel ends, the axle first should be run and then allowed to
stand for approximately 5 minutes on level ground before checking the oil level. This
allows time for the oil drain back down to the sump. Some axles have seals in the axles
separating the oil in the wheel ends from the planetary drive. In this case, the oil level is
checked independently in each wheel end and the differential banjo housing. When
checking the oil level in a top mount or inverted pinion drive axle, a slightly different
procedure must be followed. The oil hole on these units is located in the axle banjo
housing. Note that some axles have another smaller hole located just below the oil level
hole; this hole is for a temperature sensor and should not be used to fill or check the oil
level.
Figure 8-108 - Checking the oil level in an axle housing.
5.2.6 Intervals
Lubricants used in axle assemblies are necessary to provide lubrication to the internal
components and, equally important, they distribute additives throughout the axle and
wash away small wear particles that would otherwise cause accelerated wear to the
gears and bearings. The oil also carries away excess heat from high friction areas. All
these conditions, along with constant exposure to heat, lower the performance
properties of the oil. Oil analysis should be used to determine optimum oil change
intervals. Guidelines that are given in the manufacturer's service manual are based on
average operating conditions. The average temperature of lubricants in axles is
between 160°F and 220°F in summer months. Operating equipment with temperatures
above 200°F causes the oil to oxidize at a higher rate, depleting the additives that give
NAVEDTRA 14050A
8-98