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 TM 55-1905-220-14-7
3-171.3. CONNECTING ROD BEARINGS - MAINT ENANCE INSTRUCTIONS
a. The connecting rod bearing shells are precision made and are replaceable with shim adjustments.
They consist of an upper bearing shell seated in the connecting rod, and a lower bearing shell seated in the
connecting rod case. The bearing shells are prevented from endwise or radial movement by a tang at the
parting line at one end of each bearing shell.
b. Multiple layer copper-lead co-plated or aluminum triplated bearings are used. These bearings have
an inner surface (matrix) of copper-lead or aluminum. A thin deposit of babbitt is plated onto the matrix. This
babbitt overlay has excellent resistance to friction, corrosion and scoring tendencies which, combined with the
the material of the matrix, provides improved load carrying characteristics. These bearings are identified by the
satin silver sheen of the babbitt when new and a dull gray after being in service.
c. The upper and lower connecting rod bearing shells are different and are not interchangeable. Both
shells are notched midway between the bearing edges approximately 3/4 of an inch in from each parting line.
The lower bearing shell has a circumferential oil groove that terminates at the notched ends. These notches
maintain a continuous registry with the oil hole in the crankshaft connecting rod journal, and provide a constant
supply of lubricating oil to the connecting rod bearings, piston pin bushings and spray nozzle through the oil
passage in the connecting rod.
3-2918
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