TM 5-3895-359-14&P
main bearing shell or lower connecting rod bearing shell
timing gear for worn or chipped teeth.
Replace the
gears, if necessary.
the ridges are not removed, localized high unit
pressures on new bearing shells will result during engine
Check the crankshaft dowel extension. Current dowels
operation.
extend 1/2" from the crankshaft while former dowels
extend 5/8".
The ridges may be removed by working crocus cloth,
wet with fuel oil, around the circumference of the
Inspect the crankshaft for cracks as outlined under
crankshaft journal. If the ridges are greater than .0005",
Inspection for Cracks.
first use 120 grit emery cloth to clean up the ridge, 240
grit emery cloth for finishing and wet crocus cloth for
Crankshaft Measurements
polishing. Use of a piece of rawhide or other suitable
rope wrapped around the emery cloth or crocus cloth
Support the crankshaft on its front and rear journals on
and drawn back and forth will minimize the possibility of
V-blocks or in a lathe and check the alignment at the
an out-of-round condition developing (keep the strands
adjacent intermediate main journals with a dial indicator.
of rawhide apart to avoid bind). If rawhide or rope is not
used, the crankshaft should be rotated at intervals. If
When the runout on the adjacent journals is in opposite
the ridges are greater than .001", the crankshaft may
directions, the sum must not exceed .003" total indicator
have to be reground.
reading. When the runout on the adjacent journals is in
the same direction, the difference must not exceed
Carefully inspect the rear end of the crankshaft in the
.003" total indicator reading. If the runout limit is greater
area of the oil seal contact surface for evidence of a
than given in Table 1, the crankshaft must be replaced.
rough or grooved condition. Any imperfections of the oil
seal contact surface will result in oil leakage at this
CRANKSHAFT RUNOUT
point.
Max. Runout
Engine
Journals
(Total indicator
Slight ridges on the crankshaft oil seal contact surface
reading)
may be cleaned up with emery cloth and crocus cloth in
471
At No. 2 and No. 4 .002"
the same manner as detailed for the crankshaft journals.
At No. 3
.004"
If the crankshaft cannot be cleaned up satisfactorily, the
TABLE 1
oil seal may be repositioned in the flywheel housing as
outlined on Page 10-2-56.
Measure all of the main and connecting rod bearing
journals (Fig. 6). Measure the journals at several
Check the crankshaft thrust surfaces for excessive wear
places on the circumference so that taper, out-of-round
or grooving. If only slightly worn, the surfaces may be
and bearing clearances can be determined. If the
dressed with a stone. Otherwise it will be necessary to
crankshaft is worn so that the maximum journal-to-
regrind the thrust surfaces.
bearing shell clearance (with new shells) exceeds
.0044",
the
crankshaft
must
be
reground.
Check the oil pump drive gear and the crankshaft
Measurements of the crankshaft should be accurate to
the nearest .0002". Also, if the journal taper of a used
crankshaft exceeds .0015" or the out-of-round is greater
than .001 ",the crankshaft must be reground.
Also measure the crankshaft thrust surfaces (Fig. 8).
Fig. 3. Typical Ridging of Crankshaft
10-2-50
