TM 5-3825-229-14&P
6-12. CRANKSHAFT AND MAIN BEARINGS (cont)
b. Inspection (cont).
(7)
Replace bearings if nicked, scratched, worn or less than minimum thickness.
(8)
Measure diameter of main bearing journals and connecting rod journals on crankshaft with a micrometer.
Measure journals at several places on journal.
(9)
Main bearing journals should have a diameter between 2.9917 and 2.9925 in. (75.99-76.01 mm).
(10) Connecting rod journals should have a diameter between 2.2043 and 2.2051 in. (55.99-56.01 mm).
(11) Check out-of-round of main bearing journals. Out-of-round should be between 0.0003 in. (0.007 mm).
Maximum allowable wear limit out-of-round is 0.0004 in. (0.010 mm).
(12) Check out-of-round of connecting rod journals. Out-of-round should be between 0.002 in. (0.005 mm).
Maximum allowable wear limit out-of-round is 0.0003 in. (0.007 mm).
(13) Check taper of main bearing journals. Taper should be between 0.002 in. (0.005 mm). Maximum allowable
wear limit is 0.0003 in. (0.007 mm).
(14) Check taper of connecting rod journals. Taper should be between 0.0002 in. (0.005 mm). Maximum
allowable wear limit is 0.0003 in. (0.007 mm).
(15) Install main bearings (c. below) and bearing caps. Tighten screws to a torque of 90 lb-ft (123 Nm).
(16) Use an inside micrometer and check inside diameter of bearing faces.
(17) Inside diameter should be 2.9937 to 2.9957 in. (76.040-76.090 mm). Check diameters of main bearing
journals measured in (8) above. Subtract this dimension from inside diameters of main bearings. The
difference is the bearing clearance. The specified clearance between main bearings and crankshaft journal
is 0.0012 to 0.0039 in. (0.03-0.10 mm). If clearance is not as specified, replace crankshaft.
(18) Remove bearing caps and main bearings (a. above).
(19) Replace crankshaft or bearings if measurements of bearing journals are not within specifications.
c.
Installation.
NOTE
The upper main bearings are marked as to location. Bearing (13) is marked FRONT UPPER, bearing (12) is marked
UPPER INTER. Bearings (11) are marked UPPER CTR and bearing (10) is marked UPPER REAR.
(1)
Install bearings (10, 11, 12, and 13) in position in crankcase. Tang on bearing must be in slot in bearing
seat.
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