GM 12661864 Crankshaft

The crankshaft can only be removed when the engine is completely detached from the car; provided that the driveplate, crankshaft pulley, timing chain, oil pan, oil pump body, oil filter, and piston/connecting rod assemblies have been also removed. Before removal, but after loosening, check the crankshaft endplay using a dial indicator, zero it when you pry it to the rear then check it again when prying to the front from the rear; it should have average crankshaft endplay of between 0.003 - 0.010 inch. Sometimes it may not be possible to use the dial indicator; in this case, it is possible to use feeler gauges. For four cylinder models, turn both the lower crankcase and perimeter bolts gradually to a point that they can easily be unscrewed; then replace the lower crankcase bolts with new once while tightening them. Take off the lower crankcase after that, but be very careful not to lose the bearing inserts. Remove these then and for 3.4L engines lightening the main bearing cap bolts in the same manner for the 3.0L and 3.6L V6 models, remove the side bearing cap bolts. Remove the crankshaft from the engine using hoist and make sure the bearing caps of main bearings put back in position with the bearing insert in place. At installation, the engine block and crankshaft must be adsorbed; main bearing oil clearance check with Plastigage, and the width of the crushed ones relative to the scale. When clearance is not as specified, check on cleanliness and if necessary, get rid of bearing insert. On the removal of all the Plastigage residues, lubricate bearing surfaces with thin layer of grease or engine assembly for sub sequent laying of crankshaft back into place. Replace new main bearing cap bolts and tighten the bolts successively in accordance with the torque specifications and the crankshaft end play should also be checked. Then, turn the crankshaft to see if it binds; it should rotate freely with a running torque no more than 50 in-chosen units and replace the rear main oil seal.

After cleaning any Plastigage residue, apply a thin layer of grease or assembly lube to the bearing surfaces before laying the crankshaft back in place.

Install new main bearing cap bolts, tightening them in sequence to the specified torque, and then recheck the crankshaft endplay.