TM 5-4320-302-14
6-17.
CONNECTING ROD ASSEMBLY (CONT)
Location/Item
Action
Remarks
NOTE
When determining big-end bearing radial and side clearance, make sure
connecting rods and big-end bearings are properly matched and also
properly matched to the corresponding crankpin.
17.Big-end bearing radial
Take the smallest measurement of the big-end
clearance
bearing bore that is still within the tolerance limits,
measured in step 14, and subtract largest crankpin
diameter measurement measured in step 16. The
radial difference between these two measurements
is the big-end bearing clearance. It should be
0.0020 to 0.0043 inch (0.05 to 0.108 mm) under
normal conditions. Radial clearance upper limit
value is 0.0118 inch (0.3 mm). If radial clearance is
less than 0.0020 inch (0.05 mm), replace big-end
bearing and remeasure bearing bore. Make sure
radial clearance falls within tolerance limits. If radial
clearance is larger than 0.0118 inch (0.3 mm),
replace big end bearing with bearing having the next
smaller size bore.
18. Big-end bearing side
Measure crankpin width and record the measure-
clearance
ment. Subtract connecting rod width measured in
step 11. The difference is big-end bearing side
clearance and it should be 0.0067 to 0.0107 inch
(0.170 to 0.271 mm) under normal conditions. The
side clearance upper limit value is 0.0236 inch (0.6
mm). If the side clearance is less than 0.0067
(0.170
mm),
the
connecting
rod
should
be
rechecked
and
remeasured.
Replace
the
connecting rod if necessary. If the side clearance is
greater than 0.0236 inch (0.6 mm), either the
connecting rod or the crankpin fillets on the
crankshaft have worn. Recheck and remeasure
connecting rod. Replace connecting rod if width is
below tolerance limits. If not, recheck crankpin
width on crankshaft. Crankpin width should be
1.3386 to 1.3401 inches (34.0 to 34.039 mm). If
crankpin width is greater than 1.3401 inch (34.039
mm), replace crankshaft. Connecting rods and big-
end bearings may also have to be replaced.
6-134
