Crankshaft, Main Bearings, Gear, and Pulley

jackets, apply high pressure steam and water through all

(2) Drain lubricating oil by removing drain plug

block openings. Turn block in various positions while

from bottom of oil pan.

this is being done so that loose scale will be washed out.

(3) Remove transmission (para 3-16).

After oil and water passages have been cleaned and

(4) Remove starter motor (TM 10-3930-618-

block has been inspected, install expansion plugs (4, fig.

20).

3-32) and oil pressure relief valve (para 3-14). Oil gallery

(5) Remove flywheel and flywheel housing

plugs should be coated with a sealing compound and

(para 3-26).

installed flush with, or below the surface, so that they will

(6) Remove crankshaft pulley as follows:

(a) Remove locknut (1, fig. 3-33).

not interfere with fit of attached parts.

(b) Using appropriate puller, remove

3-21. Crankshaft, Main Bearings, Gear, and Pulley

pulley (2).

a. Description.

(1) Crankshaft.

The crankshaft is a

(7) Remove oil pan (para 3-12).

counterbalanced, heat-treated, steel drop forging drilled

(8) Remove timing gear cover from front plate

for pressure lubrication to main and connecting rod

(para 3-25).

bearings. It is balanced both statically and dynamically

(9) Remove lubricating oil pump (para 3-13).

and is supported by seven main bearings. Crankshaft

(10) Remove connecting rod bearing caps and

end thrust is taken by thrust flanges on each side of

bearing shells (para 3-22).

center main bearings.

(11) Remove main bearing caps and bearing

(2) Main bearings.

Main bearings are

shells as follows:

replaceable without machining. The front main bearing

(a) Remove capscrews (36, fig. 3-32)

is 1 1/16 inch long; the center main bearing is 1 7/8 inch

and lockwashers (15).

long, and the rear main bearing is 1 23/32 inch long. All

(b) Remove main bearing caps (9, 10,

intermediate bearings have an inside diameter of 2.5007

13, and 17) and bearing shells (28, 29, 34, and 35).

inches to 2.5024 inches with bearing caps tightened to

(12) Remove crankshaft (fig. 3-34).

specified torque (table 1-1). The main bearing caps are

(13) Use gear puller and remove crankshaft

attached to the cylinder block and line bored in position

timing drive gear (3, fig. 3-33) and key (5).

to receive the bearing shells. Each bearing cap is

c. Cleaning, Inspection, and Repair.

numbered and when removed should always be

(1) Clean all parts in cleaning solvent (Spec

reinstalled in respective position and corresponding to

P-S-661) and dry with compressed air.

the numbers stamped on the bottom of the cylinder

(2) Be sure to clean out the crankshaft oil

block. The upper halves of the main bearing shells are

passages.

seated in the lower part of the cylinder block. The lower

(3) Inspect crankshaft journals for scoring,

halves are held in place by the main bearing caps, each

chipping, cracking, signs of overheating, or other

of which is attached to the cylinder block by capscrews

damage. If crankshaft has been overheated (usually

and lockwashers. Each half of the bearing shell is

indicated by discolored or blue bearing journal surfaces),

prevented from radial movement by a tang at the parting

is scored, or excessively worn, then reconditioning or

line on one side of the bearing shell. A spring loaded,

replacement will be necessary.

lip-type oil seal is used at the rear of the crankshaft to

(4) Recheck crankshaft journals for fine

seal the crankcase oil from the flywheel compartment. A

cracks if signs of overheating are observed.

spring loaded, lip-type oil seal, pressed into the timing

(5) Measure crankshaft main bearing and

gear cover located on the front of the engine, is used to

connecting rod journals at several points on their

seal the crankcase oil from leaking out at the front end of

diameter to check for out-of-roundness. The specified

the crankshaft.

(3) Gear and pulley. The gear and pulley are

diameter of the main bearing journals is 2.4984 inches to

2.4994 inches; the specified diameter of the connecting

installed, in that order, on the front end (threaded end) of

rod journals is 2.1214 inches to 2.1224 inches.

the crankshaft.

(6) All main and connecting rod bearings

b. Removal. Inspection can be made of crankshaft

surfaces of the crankshaft are hardened to a depth of

main bearings and journals by removing oil pan and

0.070 inch.

removing bearing caps one at a time. If crankshaft has

d. Installation. Install crankshaft in reverse order of

been damaged, removal of engine is necessary for shaft

procedure of b above, except -

replacement.

(1) Inset key (15, fig. 3-33 into shaft.

(1) Remove engine (para 2-9).

3-40