GMC 12685656 Crankshaft Assembly

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When you want to remove the crankshaft, mount a dial indicator and touch its end with that of the crankshaft. The next step is prying it backward to zero the dial indicator and then forward to check the reading. Check whether there is a wear on the crankshaft thrust surfaces if it has an endplay more than 0.003 to 0.010 inches. Loosen main bearing cap bolts and remove caps in order to remove crankshaft from these engines. Be mindful of the weight when removing crankshafts from engines. Crankshaft installation involves placing the engine block upside down on its bottom surface and removal of main bearing caps in this position. Plastigage is used for checking the oil clearance for main bearings while the connecting rod bolts are tightened using clean engine oil on their threads according to this repair manual. The main bearing caps must now be removed by lifting them up slowly after loosening all bolts as described in this manual. Comparing these crushed Plastigage wires' widths indicates how much space between cylinder block and these rings exist-it means one should scrape off all residium that could still be stuck onto them so they can rise above them freely at any time if necessary (Hartzell, 2011). After applying lubricant onto both surfaces where they meet each other, place these connecting rod back into its original location again since new bearings have been installed (Hartzell, 2011). Changing connecting rod bearings requires cleaning mating surfaces of engine block and bearing cap plus lubing faces for inserts before tightening main bearing cap bolts using clean engine oil on bolt threads (Hartzell, 2011). Check for binding by seeing if there is any resistance when rotating by hand or recheck it after rotating through one full revolution as per instructions given in this sectional maintenance manual (Hartzell, 2011).