GM Service Manual Online
For 1990-2009 cars only

Tools Required

    • J 7872 Magnetic Base Dial Indicator Set
    • J 43690 Rod Bearing Checking Tool
    • J 43690-100 Rod Bearing Checking Tool - Adapter Kit

Cleaning Procedure


    Object Number: 1950834  Size: SH

    Important: Use care when handling the crankshaft (1). Avoid damage to the crankshaft position (CKP) sensor reluctor ring teeth (2). Nicks, burrs, or other damage to the teeth may effect on-board diagnostics (OBD) II system performance.

  1. Clean the crankshaft (1) with solvent.
  2. Thoroughly clean all oil passages and inspect for restrictions or burrs.
  3. Caution: Refer to Safety Glasses Caution in the Preface section.

  4. Dry the crankshaft (1) with compressed air.

Inspection Procedure


    Object Number: 1950857  Size: SH
  1. Perform a visual inspection of the crankshaft (2) for damage.
  2. Inspect the CKP reluctor ring teeth (1) for damage.

  3. Object Number: 1950835  Size: SH
  4. Inspect the crankshaft journals (1) for wear.
  5. Journals should be smooth with no signs of scoring, wear, or damage.

  6. Inspect the crankshaft journals for grooves or scoring (2).
  7. Journals should be smooth with no signs of scoring, wear, or damage. If not replace the crankshaft.

  8. Inspect the crankshaft journals for scratches or wear (3).
  9. Journals should be smooth with no signs of scoring, wear, or damage. If not replace the crankshaft.

  10. Inspect the crankshaft journals for pitting or embedded bearing material (4).
  11. Journals should be smooth with no signs of scoring, wear, or damage. If not replace the crankshaft.


    Object Number: 1950836  Size: SH
  12. Inspect the crankshaft key (1), key way (2), and threaded hole (3) for damage. Compare your results with the Engine Mechanical Specifications .

  13. Object Number: 1950838  Size: SH
  14. Measure the crankpins for the out-of-round. Compare your results with the Engine Mechanical Specifications .
  15. Measure the crankpins for taper. Compare your results with the Engine Mechanical Specifications .

  16. Object Number: 1959839  Size: SH
  17. Measure the crankshaft thrust wall width. Compare your results with the Engine Mechanical Specifications .

  18. Object Number: 1950841  Size: SH
  19. Measure the crankshaft runout.
  20. Use wooden V blocks or a fixture to support the crankshaft on the front and rear journals.

  21. Use the J 7872 in order to measure the crankshaft run out at the front and rear intermediate journals. Compare your results with the Engine Mechanical Specifications .
  22. Use the J 7872 in order to measure the run out of the crankshaft rear flange. Compare your results with the Engine Mechanical Specifications .
  23. Use the J 7872 in order to measure the run out of the crankshaft position reluctor ring. Compare your results with the Engine Mechanical Specifications .

  24. Object Number: 1950843  Size: SH
  25. Check the rear crankshaft oil gallery plug (1) for a loose fit or evidence of leaking.
  26. Important: If a manual transmission is fitted to the vehicle, it will be necessary to first remove the clutch pilot bearing. Refer to Clutch Pilot Bearing Replacement .

  27. If replacement is required, apply sealant such as Loctite 242 or equivalent, to the sides of a new plug (1) and install to the correct depth.
  28. Specification
    Crankshaft rear oil gallery plug depth specification: Distance A 31.2 - 31.6 mm.


    Object Number: 1950844  Size: SH
  29. Inspect crankshaft bearings for craters or pockets. Flattened sections on the bearing halves also indicate fatigue.

  30. Object Number: 1950846  Size: SH
  31. Inspect the crankshaft bearings for above acceptable scoring or discoloration.
  32. Inspect the crankshaft bearings for dirt or debris embedded into the bearing material.

  33. Object Number: 1950847  Size: SH
  34. Inspect the crankshaft bearings for incorrect seating indicated by bright, polished sections of the bearing.
  35. If the lower half of the bearing is worn or damaged, both upper and lower halves should be replaced.

    Generally, if the lower half is suitable for use, the upper half should also be suitable for use.

Measuring Main Bearing Clearance - Gauging Plastic Method


    Object Number: 1950849  Size: SH

    Important: 

       • The crankshaft main bearings are a precision insert type. Main bearing caps are machined with the engine block for correct clearance and cannot be shimmed or filed for bearing fit. If the clearances are found to be above acceptable tolerances, new bearings and/or engine block and cap repair or replacement may be required.
       • Do not rotate the crankshaft while gauging plastic is between the crankshaft journal and the bearing surface.
       • The crankshaft bearing clearances are critical. Above acceptable bearing clearance may effect CKP sensor signals and may effect on-board diagnostics  (OBD) II system operation.
       • Remove the bearing cap side bolts prior to cap removal.

  1. Install gauging plastic (1) onto the crankshaft journal. Install the gauging plastic the full width of the crankshaft bearing journal.
  2. Install the bearing caps, bearing half, and bolts. Refer to Crankshaft and Bearing Installation .
  3. Remove the bearing caps, bearing half, and bolts. Refer to Crankshaft and Bearing Removal .

  4. Object Number: 1950851  Size: SH
  5. Measure the gauging plastic at its widest area using the scale supplied with the plastic gauging kit.
  6. • If the gauging plastic shows irregularity in the journal exceeding 0.025 mm (0.001 in), remove the crankshaft and measure the journal with a micrometer.
    • If clearance cannot be brought to specifications, replace the crankshaft or engine block as required. Refer to Engine Mechanical Specifications .

Measuring Connecting Rod Bearing Clearance - Gauging Plastic Method


    Object Number: 1950855  Size: SH

    Important: 

       • Connecting rod bearings are a precision insert type. Connecting rods are of a powdered metal design and cannot be shimmed or filed for bearing fit. If clearances are found to be above acceptable tolerances, a new bearing and/or connecting rod are required.
       • Do not rotate the crankshaft while gauging plastic is between the crankshaft journal and the bearing surface.

    Important: Install the gauging plastic (1) the full width of the journal.

  1. Install the gauging plastic (1) onto the connecting rod bearing journal.
  2. Install the bearing cap, bearing half, and bolts. Refer to Piston, Connecting Rod, and Bearing Installation .
  3. Remove the bearing cap, bearing half and bolts. Refer to Piston, Connecting Rod, and Bearing Removal .

  4. Object Number: 1950856  Size: SH
  5. Measure the gauging plastic at its widest area using the scale supplied with the plastic gauging kit. Refer to Engine Mechanical Specifications .