TM 5-3895-359-14&P
crankshaft journals. This clearance may be determined
with the crankshaft in place by means of a soft plastic
measuring strip which is squeezed between the journal
and the bearing (refer to Shop Notes on Page 10-2-
131). With the crankshaft removed, measure the outside
diameter of the crankshaft main bearing journals and
the inside diameter of the main bearing shells when
installed in place with the proper torque on the bearing
cap bolts. When installed, the bearing shells are .001 "
larger in diameter at the parting line than 90 from the
parting line.
The bearing shells do not form a true circle when not
installed. When installed, the bearing shells have a
squeeze fit in the main bearing bore and must be tight
when the bearing cap is drawn down. This crush
assures a tight, uniform contact between the bearing
shell and bearing seat. Bearing shells that do not have
sufficient crush will not have uniform contact, as shown
by shiny spots on the back, and must be replaced. If the
clearance between any crankshaft journal and its
bearing shells exceeds .0060 ", all of the bearing shells
must be discarded and replaced. This clearance is .0014
Fig. 8. Crankshaft Thrust Washers in Place
" to .0044 " with new parts.
Before installing new replacement bearings, it is very
Inspect the crankshaft thrust washers. If the washers
important to thoroughly inspect the crankshaft journals.
are scored or worn excessively or the crankshaft end
Very often, after prolonged engine operation, a ridge is
play is excessive. they must be replaced. Improper
formed on the crankshaft journals in line with the journal
clutch adjustment can contribute to excessive wear on
oil holes. If this ridge is not removed before the new
the thrust washers.
Inspect the crankshaft thrust
bearings are installed, then, during engine operation,
surfaces. Refer to Install Crankshaft on Page 10-2-53.
localized high unit pressures in the center area of the
If, after dressing or regrinding the thrust surfaces, new
bearing shell will cause pitting of the bearing surface.
standard size thrust washers do not hold the
Also, damaged bearings may cause bending fatigue and
crankshaft end play within the specified limits, it may be
resultant cracks in the crankshaft. Refer to Page 10-2-
necessary to install oversize thrust washers on one or
49 under Crankshaft Inspection for removal of ridges
both sides of the rear main bearing. A new standard
and inspection of the crankshaft.
size thrust washer is .1190 " to .1220 " thick. Thrust
washers are available in .005 " and .010" oversize.
Do not replace one main bearing shell alone. If one
bearing shell requires replacement, install all new upper
Install Main Bearing Shells (Crankshaft in Place)
and lower bearing shells. Also, if a new or reground
Make sure all of the parts are clean. Then apply clean
crankshaft is to be used, install all new bearing shells.
engine oil to each crankshaft journal and install the
Bearing shells are available in .010 ", .020 " and
upper main bearing shells by reversing the sequence of
.030 " undersize for service with reground crankshafts.
operations given for removal.
To determine the size bearings required, refer to
The upper and lower main bearing shells are not alike;
Crankshaft Grinding on Page 10-2-52. Bearings which
the upper bearing shell is grooved and drilled for
are .002 " undersize are available to compensate for
lubrication -- the lower bearing shell is not. Be sure to
slight journal wear where it is unnecessary to regrind the
install the grooved and drilled bearing shells in the
crankshaft.
cylinder block and the plain bearing shells in the bearing
NOTE
caps, otherwise the oil flow to the bearings and to the
Bearing shells are NOT reworkable
upper end of the connecting rods will be blocked off.
from one undersize to another under
Used bearing shells must be reinstalled on the same
journal from which they were removed.
any circumstances.
1. When installing an upper main bearing shell with the
crankshaft in place, start the plain end of the bearing
shell around the crankshaft journal so that,
10-2-62
