Mitsubishi 3000GT 1991 Service Manual page 34

WHEEL BEARING TROUBLESHOOTING
Trouble
Pitting
Flaking
Cracking
Flat spotting
Nicks
Smearing
Rust, corrosion
Wear
Discoloration
GENERAL
Symptom
Pitting occurs because of uneven rotation of race
and bearing surfaces
The surface peels because of uneven rotation of
the race and bearing surfaces
Chipping or cracking of cage or roller edges
When large load is applied, race and roller
contact surfaces compress, forming
indentations
Instead of rolling along race surface, rollers
slide, thus damaging surface
Damage or wear caused by minute particles
adhering to surfaces results in rough movement
and such high temperatures that parts of surface
melt
Appears on various areas of the bearing
Wear of surface areas caused by friction
Grease discoloration results from grease
deterioration which causes particles of pigment
contained in grease to adhere to surfaces
Heat discoloration will appear as a deep brown or
purple
TSB Revision
Probable cause
Excessive bearing preload
Excessive load
End of bearing life
Improper bearing assembly
Impact when bearing was
installed (such as being hit with
a hammer)
Excessive bearing preload
Excessive load
Vibration when bearings are not
used, such as during shipment
on freight cars, transport trucks,
etc.
Insufficient grease
Excessive bearing preload
Excessive load
Faulty oil seal
Excessive variation of loads on
bearings
Use of grease other than that
specified
Insufficient grease
Use of grease other than that
specified
Faulty oil seal
Presence of water or moisture
Insufficient grease
Foreign matter
Rust or corrosion due to
moisture
Use of grease other than that
specified
Faulty oil seal
Use of grease other than that
specified
Faulty oil seal
Excessive bearing preload
Excessive load