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Home >> GMC >> 2006 >> Sierra 1500 HD, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 10 (Engine Mechanical - 8.1L) >> Repair Instructions >> Off-Vehicle Repair Instructions >> Crankshaft and Bearings Cleaning and Inspection >> Micrometer Method for Crankshaft Bearings

Micrometer Method for Crankshaft Bearings

WARNING: This page is about a different variant/trim than selected.
    Fig 1: Measuring Crankshaft Journals
    GM35207Courtesy of GENERAL MOTORS CORP.
    IMPORTANT: When bearings are removed, NEW bearings must be installed during reassembly.
  1. Measure the crankshaft main journal diameter with a micrometer in several places along the length approximately 90 degrees apart, minimum of 4 places, and average the measurements.
  2. Determine the taper and the out-of-round. Refer to Engine Mechanical Specifications .
  3. Fig 2: View Of Crankshaft Bearings & Crankshaft Bearing Caps
    GM639521Courtesy of GENERAL MOTORS CORP.
  4. Install the NEW crankshaft bearings into the crankshaft bearing caps and the engine block.
  5. NOTE: Refer to Fastener Notice in Cautions and Notices.
    IMPORTANT: Tighten the crankshaft bearing cap bolts before tightening the crankshaft bearing cap studs.
  6. Install the bearing cap bolts and studs.

    Tighten: 

    1. Tighten the bearing cap bolts a first pass to 30 N.m (22 lb ft).
    2. Tighten the bearing cap studs a first pass to 30 N.m (22 lb ft).
    3. Tighten the bearing cap bolts a final pass an additional 90 degrees using the J 45059  .
    4. Tighten the bearing cap studs a final pass an additional 80 degrees using the J 45059  .

  7. Measure the crankshaft bearing inside diameter (ID) using an inside micrometer. Measure at a minimum of four places and average the measurements.
  8. In order to determine the crankshaft bearing clearance, subtract the crankshaft journal diameter from the crankshaft bearing ID.
  9. Compare the crankshaft bearing clearance to the specifications. Refer to Engine Mechanical Specifications .
  10. If the crankshaft bearing clearances exceeds specifications, install undersize crankshaft bearings to achieve the correct clearance.
  11. Measure the new crankshaft bearing inside diameter (ID) using an inside micrometer.
  12. Replace the crankshaft if the proper clearances cannot be obtained with standard size bearings.