TM 5-6115-400-35
than they are 90 from the parting line,
Caution:
and do not form a true circle. The two
Make certain the backs of the bearing
halves of the shells have a crush fit in
shells are free from dirt and grit
their bore in the block and must be tight
particles.
when the cap is secured in place. Do not
(2) Lubricate all crankshaft main bearing
measure inside diameter at the parting
journals, install crankshaft and main
line. The specified inside diameter of new
bearing caps, and check crankshaft end
main bearings is 3.9981 inches-3.9998
inches and any reading above 3.9998
e. Main Bearing Replacement with Engine
inches indicates the amount of bearing
Installed. It is
unwise to
replace main bearings without
wear. Measure diameter of the crankshaft
removing the engine and taking it into a clean shop
journal at the corresponding bearing
where disassembly and inspection can be effected
location and subtract this dimension from
properly; however, when removal of the engine is
inside diameter measurement of the
impractical or in emergency cases, the following
bearing (as determined above); the
procedure may be used.
difference
between
these
two
(1) Main bearing removal with engine
measurements is the crankshaft-to-
installed.
bearing clearance.
(a) Remove fuel injection nozzle
(3) Another method for determining amount
holders from engine to relieve
of wear on bearing shells is by measuring
compression and allow free turning
of the crankshaft.
90from the parting line. New shells are
(b) Drain oil from oil pan and remove
.1876 inch-.1881 inch thick.
Bearing
the oil pan, oil pump, and
shells less than .186 inch thick are worn
associated tubing.
Refer to
beyond the allowable limits and must be
replaced.
(c) Remove only one main bearing cap,
(4) The most accurate method of determining
install new bearing, reinstall bearing
main bearing clearance is by using
cap, and tighten cap retaining
capscrews to the specified torque
preceding paragraphs. However, if the
before removing next bearing cap.
or the crankshaft is installed in the engine,
(d) The lower bearing shell can be
bearing clearance may be measured by
removed from the bearing cap after
using a plastic strip manufactured for this
cap is removed. Remove upper
purpose. The plastic strip must be used in
bearing shell as follows. Insert a
accordance with the manufacturer's
inch X 1 inch capscrew, with the
instructions.
head ground down to a thickness of
approximately 3/32 inch, into the
(5) Main bearings are available in standard
crankshaft main bearing oil hole, or
thickness (.1876 inch-.1881 inch) and
a cotter pin with the head flattened,
.010 inch, .020 inch, .030 inch, and .040
inch undersize.
crankshaft in the direction that will
d. Main Bearing Installation.
turn head of the bolt against an end
(1) Install a main bearing shell in each of the
of the bearing shell.
Continue
bearing seats in the cylinder block.
rotating crankshaft until bearing
shell has been pushed out. The
upper half of the rear main bearing
shell may be rolled out of place by
driving on the edge of bearing shell
130