Section VI. CRANKSHAFT AND MAIN BEARINGS

TM 10-3930-630-34

Section VI. CRANKSHAFT AND MAIN BEARINGS

Blow out oil passages with filtered compressed air.

11-34. Description

b. Place crankshaft in "V" blocks. Place oil soaked

The crankshaft is forged of special heat treated steel.

paper strips in blocks before installing crankshaft to

Rifle drilled passages carry oil to the connecting rods

prevent marring of bearing surfaces.

and main bearings.

c. Take a dial indicator reading at the center main

bearing journal. Total run-out for center main bearing

11-35. Crankshaft and Main Bearing, Removal and

journal must not exceed 0.002 inch (0.050 mm).

Disassembly

d. Check the main bearing and connecting rod

a. Removal

journals for out-of-round or tapered condition.

(1) Refer to paragraph 2-22, drain the engine

Maximum allowable out-of-round condition is 0.0005

oil and remove the engine from the truck.

inch (0.0127 mm).

(2) Install the engine in an engine stand.

e. If journals are scored or worn, the crankshaft

(3) Refer to paragraph 11-7 and remove the oil

must be reground or replaced.

pan. Refer to paragraph 11-17 and remove connecting

f. Measure diameter of connecting rod journals.

rod bearing caps and bearings.

(1) Diameter must be 2.0627 to 2.0618 inches

(4) Refer to paragraph 11-21 and remove the

(52.39 to 52.37 mm).

gear cover and fan drive.

(2) Minimum diameter wear limit is 2.0609

(5) Refer to paragraph 11-28 and remove the

inches (52.34 mm).

flywheel.

g. Measure diameter of main bearing journals.

(6) Refer to paragraph 11-31 and remove the

(1) diameter should be 2.3752 to 2.3744

flywheel housing.

inches (60.33 to 60.30 mm).

(7) Refer to paragraph 11-10 and remove the

(2) Minimum diameter wear limit is 2.3734

oil pump.

inches (60.28 mm).

b. Disassembly. Disassemble the crankshaft and

h. Do not grind crankshaft journals to remove more

main bearings in numerical sequence as illustrated in

than 0.040 inch (1.01 mm).

figure 11-39.

i. When reground, the crankshaft fillet radii must

be within limits and must be perfectly blended into thrust

11-36. Crankshaft and Main Bearing, Cleaning,

and bearing surfaces as shown on figure 11-40.

Inspection and Repair

a. Clean crankshaft with cleaning compound,

solvent (Fed. Spec. P-D-680) and dry thoroughly.

11-25