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 TM 55-1905-221-14-3
6-28.1.
CRANKSHAFT BEARINGS - MAINTENANCE INSTRUCTIONS (Continued).
LOCATION/ITEM
ACTION
REMARKS
INSPECTION
4. Upper Bearing
a. Clean and inspect for scoring,
Shells and
pitting, flaking, etching,
Lower Bearing
loss of babbitt, and signs of
Shells
overheating. The lower bear-
ing shells which carry the
load will normally show signs
of distress before the upper
bearing shells. However,
babbitt plated bearings may
develop minute cracks or small
isolated cavities on the bear-
ing surface during engine
operation. These are char-
acteristics of and are not
detrimental to this type of
bearing. They should not be
replaced for these minor sur-
face imperfections since
function of the bearings Is
in no way impaired and they
will give many additional
hours of trouble-free
operation.
b. Inspect the backs of the bear-
ing shells for bright spots
which indicate they have been
moving in the bearing caps or
bearing supports. If such
spots are present, discard the
bearing shells.
c.
Measure the thickness of the
Use micrometer
bearing shells at point "C",
ball attachment
90 from the parting line.
J4757.
Tool J5347-01, placed between
the bearing shell and a micro-
meter, will give an accurate
measurement. The bearing
shell thickness will be the
total thickness of the steel
ball in the tool, and the
bearing shell, less the dia-
meter of the ball. This is
the only practical method for
6-490
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