TRUCK SERVICE MANUAL
ENGINE
2. Total worn maximum oil clearance should not vary
more than 0.002 inch [0.05 mm] between adjacent main
bearings. See Table 1-1 (7-8).
Note: Under no circumstances should an attempt be made to
scrape bearing shells, nor should they be lapped or filed to
increase oil clearances. A properly fitted bearing will appear
dull gray after a reasonable period of service, indicating it is
running on an oil film. Bright spots indicate metal-to-metal
contact and black spots indicate excessive clearance.
CRANKSHAFT THRUST RINGS
1. The best measurement of wear on crankshaft thrust
rings is the crankshaft end clearance check. See "Engine
Fig .
143 (V50138) Identification of rod and main journal size
Assembly" Group 14 and Table 1-1 (9-10).
2. Oversize thrust rings are available; be sure to use
same size (thickness) half-ring on both upper and lower
portions. Stamp crankshaft rear counterweight indicating size
used.
Note: Allowable amount of wear on thrust ring depends upon
wear of crankshaft surfaces. Installed in a cylinder block,
crankshaft end clearance should not exceed 0.022 inch [0,56
mm] at rebuild; however, at the maintenance check, when
engine is operating satisfactorily, end clearance is allowable to
maximum of 0.035 inch [0.89 mm on 855 series engines.
VIBRATION DAMPER
The vibration damper is a unit which counteracts twisting or
torsional vibrations of crankshaft. The damper is engineered
to match engine model on which it is used. To prevent failures
make sure it is operative at all times. Two types of vibration
Fig .
1-4 .
(N101140) Oversize thrust bearing mark on
dampers are used on Cummins engines rubber element and
crankshaft
viscous.
CLEANING
c . Lubricate flange with high pressure grease and drive
Viscous dampers should be cleaned of rust, dirt or grease
gear onto shaft with piece of tubing.
with a suitable solvent cleaner.
d. Install lockplate and nut (if used).
Dampers are not subject to Field repair; therefore, if inspection
shows them to be defective, install new dampers.
BEARINGS
Rubber Element Damper
Main and connecting rod bearings (or shells) are two-piece
Most engines use rubber element dampers, which are tuned to
units with one unit containing an oil hole for lubrication. Thrust
the engine's natural system frequency. These are made of
rings are used at the rear main bearing.
metal units separated by rubber compound material. The
dampers are designed to provide adequate protection for
INSPECT BEARING SHELLS
1. Gauge shell with ball point micrometer, dial indicator
thickness gauge, or comparator. Discard shells that are worn
more than 0.001 inch [0.03 mm] or if chipped, flaked, or
scored. See Table 1-1 (7-8) for thickness of standard shells.
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