TM 5-3895-346-14
CONNECTING ROD
ENGINE OVERHAUL
A service connecting rod includes the bearing cap, bolts, nuts, spray nozzle (if used), orifice, and the piston pin
bushings pressed in place and bored to size.
Disassemble Connecting Rod from Piston
With the rod and piston assembly removed from the engine, disassemble the piston and connecting rod as
outlined in Piston and Piston Rings.
Inspection
Clean the connecting rod and piston pin with fuel oil and dry them with compressed air. Blow compressed air
through the drilled oil passage in the connecting rod to be sure the orifice, oil passage, and spray holes are not
clogged.
Visually check the connecting rod for twisting or bending. Check for cracks (Fig. 3) by the magnetic particle
method under Crankshaft Inspection.
If a new service connecting rod is required, stamp the cylinder number on the connecting rod and cap (refer to
Cylinder Liner).
CAUTION
Clean the rust preventive from a service replacement connecting rod and blow
compressed air through the drilled oil passage to be sure the orifice, oil passage,
and spray holes are not clogged. Also make sure the split line (cap to rod) is
thoroughly cleaned to avoid trapped contaminants from adversely affecting bearing
shell crush.
Check the connecting rod bushings for indications of scoring, overheating, or other damage. Bushings that
have overheated may become loose and creep together, thus blocking off the supply of lubricating oil to the
piston pin, bushings, and spray nozzle.
Inspect the piston pin for signs of fretting. When reusing a piston pin, the highly polished and lapped surface of
the pin must not in any way be refinished. Polishing or refinishing the piston pin is not recommended as it
could result in very rapid bushing wear.
Since it is subjected to downward loading only, free movement of the piston pin is desired to secure perfect
alignment and uniform wear. Therefore, the piston pin is assembled with a full-floating fit in the connecting rod
and piston bushings, with relatively large clearances. Worn piston pin clearances up to 0.010 inch are
satisfactory.
Remove Bushings
If it is necessary to replace the connecting rod bushings, remove them as follows:
1.
Clamp the upper end of the connecting rod in holder J 7632 (Fig. 4) so that the bore in the
bushings is aligned with the hole in the base of the holder.
2.
Place bushing remover J 4972-4 in the connecting rod bushing, insert handle J 1513-2 in the
remover, and drive the bushings from the rod.
Replace Spray Nozzle
The connecting rod bushings must be removed before the spray nozzle can be replaced. The orifice in the
lower end of the drilled passage in the connecting rod is not serviced and it is not necessary to remove it when
replacing the spray nozzle.
Replace the spray nozzle as follows:
1. Remove the connecting rod bushings.
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