GMC 12555637 Crankshaft

Remove all burrs from the crankshaft oil holes with a stone, file, or scraper to ensure the oil holes are chamfered, preventing sharp edges from gouging or scratching the new bearings. Clean the crankshaft with solvent and dry it with compressed air if available, ensuring to clean the oil holes with a stiff brush and flush them with solvent. Check the main and connecting rod bearing journals for uneven wear, scoring, pits, and cracks, and inspect the rest of the crankshaft for cracks and other damage, which should be magnafluxed by an automotive machine shop to reveal hidden issues. Using a micrometer, measure the diameter of the main and connecting rod journals at several points to detect taper and out-of-round conditions, taking measurements at each end of the journal near the crank throws. If the crankshaft journals are damaged, tapered, out-of-round, or worn beyond specified limits, have the crankshaft reground by an automotive machine shop, ensuring the use of the correct size bearing inserts if reconditioned. Check the oil seal journals at each end of the crankshaft for wear and damage; if grooves, nicks, or scratches are present, the new seal may leak upon reassembly. In some cases, an automotive machine shop may repair the journal by pressing on a thin sleeve, but if repair isn't feasible, a new or different crankshaft should be installed. Examine the main and rod bearing inserts for further assessment.