Replace the hanger bearing if there is evidence of damage. Do not attempt to
repair or lubricate it.
4.3.0 Lubrication
One of the most common causes of U-joint and slip joint problems is the lack of proper
lubrication. If U-joints are properly lubricated at recommended service intervals, they will
meet or exceed their projected operating life span. Regular lubing ensures that the
bearings have adequate grease and, additionally, that the trunnion races are flushed,
which removes contaminants from
the critical surface contact areas.
Clean grease fittings thoroughly to
remove accumulated grease and
abrasives before use. Any
contaminants and abrasives can
be forced through the grease
fitting into the bearing during
lubing.
A hole in each trunnion leads to
the center of the cross (
Figure 8-
51
). A grease fitting often
connects to the center of the
cross. Grease injected through the
fitting flows through the holes in
the trunnions to each needle
bearing. Some universal joints are
sealed at the factory and cannot
be greased unless they are
disassembled.
4.3.1 4.3.1 U-Joint Lubricants
Heavy duty driveshafts typically
Figure 8-51 - Internal passageways in this
cross-and-roller universal joint act as a
grease reservoir.
use lithium soap-based extreme pressure (EP) grease, National Lubricating Grease
Institute classification grades 1 and 2 specifications. Grades 3 and 4 are not
recommended; because of their greater thickness they are less effective in the cold.
Most lubed-for-life bearings use synthetic greases. When replacing a U-joint, note that
the grease in the U-joint is only there to protect it during shipping and storage. Lubing
the U-joint after installation is a service requirement and should never be put off.
Lubrication schedules can vary greatly depending on operating conditions. Off-road
equipment generally requires that the severe duty cycle recommendations on lube
charts be followed. Off-road classifications are generally considered to apply to
equipment that operates on unpaved roadways for 10% or more of the time.
4.3.2 Lubricating a U-Joint
1. Apply chassis grease through either one of two zerk fittings on the U-joint cross.
Fit the grease nozzle over the zerk nipple. Pump grease slowly into the fitting
until each of the four trunnion seals pops. Allow a small quantity of the old grease
to be forced out of the bearings. This flushes contaminants out of the bearings
and helps ensure that all four have taken grease. The U-joint is properly greased
when evidence of purged grease is seen at all four bearing trunnion seals.
NAVEDTRA 14050A
8-55