However, the crankshaft can only be removed if the engine has been mobil out of the vehicle presuming that the driveplate, crankshaft pulley, timing chain, oil pan, oil pump, the oil filter, and piston/connecting rod assemblies have to be removed. To do this check the end play on the crank shaft before removal of the bearing by using a dial indicator. Place the tip of the indicator at the center of the crankshaft pulley and pry the crankshaft to the rear till the same shines in the aiming bulb and zero the indicator then pry the crankshaft to the front and the reading should be between 0.003-0.010 inch. If the endplay is outside this range, measure the wear of the thrust washer/bearing assembly. However, if you cannot access dial indicator, you can use feeler gauges for coming to clearance measurements. Unfasten the side-bolts of the main bearing cap while turning it with your fingers, and then strike the caps lightly with a battle-axe. With some effort, slowly pull the crankshaft up, preferably with another person's help and then, place the main bearing cap assembly in their rightful place, with the arrow pointing to the front of the engine, if it is from AC Delco. For installation, some of the requirement include: The engine block and crankshaft has be cleaned or inspected. SO, place the block in such a way that the bottom is upward, then loosen and take off the main bearing caps, and then clean the bearing surfaces. New main bearing inserts are fitted and the oil holes should match, the lower inserts have to go into the caps. Verify the amount of the two bearings, employing Plastigage in order to get a clearance level of the main bearing oil that ranges from 0.0015 to 0.0023 inch. If clearance is improper, check that no solid phase was present during the measurement and that inserts may need to be changed in some cases. Once you removed the Plastigage residue, it is crucial to lubricate the thrust or journal bearing faces with special grease or assembly lube before reinstalling the crankshaft. Place the main bearing caps with the arrow pointing forward, torque the bolts intended for M/B consistent with the recommended sequence. Recheck crankshaft end play and turn the crankshaft and see that there is no binding when turning this shaft. Last, replace the new rear main oil seal on the engine of the car.
Posted by NissanPartsDeal Specialist 
