TM 10-4320-307-24
4-17
CRANKSHAFT ASSEMBLY REPLACE, REPAIR (CONT)
4.
Check crankshaft alignment as follows:
a.
Check
short
bend
alignment
at
adjacent main bearing journals (1) with
dial
indicator
(2).
The
maximum
allowable runout is 0.002 inch (0.0508
mm). Replace crank-shaft if necessary.
b.
Check
full
length
alignment
by
supporting crankshaft at end main
bearing
journals
and
setting
dial
indicator probe on center main bearing
journal.
c.
With
dial
indicator
zeroed,
rotate
crankshaft one revolution and read
maximum deflection of dial indicator for
total indicated runout.
d.
Maximum
allowable
total
indicated
runout is 0.002 inch (0.0508 mm).
Replace crank-shaft if necessary.
5.
Inspect main bearing shells. A shell which was fitted properly will be grey. Light areas on shell indicate that metal is
touching metal, without enough oil clearance. Dark areas on shell indicate that clearance is too large.
6.
Measure thickness of main bearing shells with a micrometer that has a ball point. The minimum acceptable thickness
for shells is 0.1215 inch (3.086 mm). Discard shells which are worn beyond this thickness or have scratches or other
damage.
Bearing Clearance - Inch (mm)
Bearing
New Dimension
Journal
Minimum
Maximum
Worn Limit
Main
0.1230
0.1238
0.1215
Bearing
(3.124)
(3.145)
(3.086)
NOTE
Bearing shells are available for crankshafts that are 0.010 inch (0.25 mm), 0.020 inch (0.51 mm), 0.030
inch (0.76 mm), or 0.040 inch (1.02 mm) undersize. Crankshafts that are ground undersize in the
connecting rod and main bearing journals are marked on the front counter weight. If the crankshaft is
marked, check the bearing shell part number to make sure the correct bearing size is used.
4-127
