SERVICE MANUALCRANKSHAFT, MAIN BEARINGS, FLYWHEEL & CRANKCASESection 6GeneralCRANKSHAFTThe crankshaft is fully counterbalanced and the journalsare induction hardened. The D and DT-466 engines arealso fillet hardened. There are seven main bearings,with the number - 7 (rear) bearing absorbing the endthrust. The crankshaft extension at the foreward endcarries the main drive gear, a splined collar (which drivesthe lubricating oil pump) and the vibration damper. Thegear and splined collar are a shrink fit and the damper, apress fit. The damper hole is keyed to the shaft and heldin place by a retainer plate. The flywheel is mounted tothe rear end of the crankshaft. Two seals, one at thefront and one at the rear, prevent leakage of enginelubricating oil around the ends of the crankshaft.MAIN BEARINGSBearing caps are furnished with the crankcase and thesesupport the crankshaft in true alignment. Webs integralwith the crankcase provide the upper half of the mainbearing supports and removable caps provide the lowersupport. The caps are held in place with cap screws.The bearing caps are NOT interchangeable, and eachhas a number stamped upon it which signifies its correctlocation in the crankcase, as shown in Fig. 3. Number 1is at the front of the engine.Figure 3. - Bearing Cap (Top View) IdentificationNumberFLYWHEELThe flywheel Is attached to the rear of the crankshaft. Itspurpose is to oppose and moderate by its inertia anyfluctuations in the speed of the engine. It counteractsvariable torque’s during the stroke of the engine, andprovides a rotating balance weight that carries the enginecrankshaft over dead centers on the pistons.It is secured to the end of the crankshaft with bolts. Thecranking motor drive ring gear is a shrink fit and isreplaceable.CRANKCASEThere are two basic crankcases used: one for the 300Series and one for the 400 Series Engines. The maindifferences are the physical dimensions; the 400 Seriescase is longer and higher.All crankcases have seven main bearing areas with thethrust bearing saddle located at the rear. All cases areline bored with the caps in place and the bolts tightenedto the specified torque. All caps are marked and are notinterchangeable within the case itself or with other cases.On Turbocharged engines, each main bearing web hasangled-drilled holes, which are fitted with coolant jettubes that direct lubricating oil, under pressure, to theunderside of each piston. A percentage of the lubricatingoil fed to the main bearings passes through milled slotsin the upper half of the bearing shells. The stream of oilfrom these jets is a constant flow during all periods ofengine operation. N.A. engine crankcases have thetwelve oil-jet holes plugged with balls.There are two oil galleries cast into the case; onehandles unfiltered oil from the pump to the cooler andthen from the cooler to the filter base. Oil leaving thefilter enters the second gallery and is distributed tovarious points of lubrication throughout the engine. Bothgalleries are sealed at the front and rear of the case withplugs. The camshaft is located directly above thesegalleries and is supported on finished bushings pressedinto the case.CGES-185-3PRINTED IN UNITED STATES OF AMERICAPage 3
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