TM 5-2420-230-24-2
B3.9 and B5.9 Series Engines
Bearings, Connecting Rod (001-005)
Section 1 - Cylinder Block - Group 01
Page 1-5
Bearings, Connecting Rod (001-005)
General Information
In production, steel-backed aluminum connecting rod bear-
ings are used for naturally aspirated engines. Steel-backed
trimetal bearings are used in production for the additional
loading, resulting from turbocharging and aftercooling.
To prevent incorrect use of the two bearings at time of
repair, only steel-backed trimetal bearings are available for
service.
Improper maintenance of the lubrication system is the pri-
mary cause of reduced bearing life.
An oil analysis will aid in determining the extent of internal
engine damage; refer to Section 7 for more information.
For additional oil analysis, refer to the Cummins Engine Oil
Recommendations, Bulletin No. 3810340.
Normally, worn bearings can be detected by reduced oil
pressure, but if this wear goes undetected, the excessive
clearance will increase the impact between the bearing
and crankshaft causing a distinct knocking sound.
L-683
