GM Service Manual Online
For 1990-2009 cars only

In order to determine the correct replacement bearing size, the bearing clearance must be measured accurately. Either the micrometer or plastic gauge method may be used, however, the micrometer method gives more reliable results and is preferred. Refer to Crankshaft and Bearing Cleaning and Inspection for the micrometer method.

The crankshaft bearings are of the precision insert type and do not use shims for adjustment. If the clearances are excessive, the new upper and the lower bearings will be required. The service bearings are available in the standard size and an undersize.

    • 0.001 in
    • 0.002 in
    • 0.010 in
    • 0.020 in

The selective fitting of the crankshaft bearings are necessary in production in order to obtain close tolerances. For this reason, you may use one-half of a standard crankshaft bearing with one-half of a undersize crankshaft bearing.

Notice: Do not shim, scrape, or file bearing inserts. Do not touch the bearing surface of the insert with bare fingers. Skin oil and acids will etch the bearing surface.

Plastic Gauge Method

  1. Install the crankshaft bearings into the crankshaft bearing cap and the engine block.
  2. Install crankshaft.

  3. Object Number: 4980  Size: SH
  4. Install the gauging plastic on the crankshaft main journal perpendicular to the crankshaft bearing.
  5. Notice: In order to prevent the possibility of cylinder block or crankshaft bearing cap damage, the crankshaft bearing caps are tapped into the cylinder block cavity using a brass, lead, or a leather mallet before the attaching bolts are installed. Do not use attaching bolts to pull the crankshaft bearing caps into the seats. Failure to use this process may damage a cylinder block or a bearing cap.

  6. Install the crankshaft bearing caps and the bolts. Ensure that the arrows on the crankshaft bearings caps are facing the front of the engine.
  7. Important: Tighten inside bearing cap bolts first and outside bearing cap bolts last.

    Tighten
    Tighten the bolts to 135 N·m (100 lb ft).

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.

  8. Remove crankshaft bearing cap bolts and caps.

  9. Object Number: 61038  Size: SH
  10. Measure gauging plastic.
  11. • Gauging plastic may adhere to either the crankshaft bearing or crankshaft journal.
    • Without removing the gauging plastic, measure the compressed width at the widest point using a graduated scale provided on the gauging plastic envelope.
  12. If the flattened gauging plastic tapers toward the middle or the ends, there is a difference in clearance indicating taper, low spot or other irregularity of the bearing or the journal.
  13. Normally the crankshaft bearing journals wear evenly and are not out-of-round. However, if a bearing is being fitted to an out-of-round 0.0254 mm (0.001 in maximum) journal, be sure to fit to the maximum diameter of the journal. If the bearing is fitted to the minimum diameter and the journal is excessively out-of-round, the interference between the bearing and the journal will result in rapid bearing failure.
  14. If the bearing clearance is within specifications, the bearing is satisfactory. If the clearance is not within specifications, replace the bearing. Always replace both the upper and the lower bearings as a unit.
  15. A standard or undersize bearing combination may result in the proper clearance. If the proper bearing clearance cannot be achieved using the standard or the undersize bearings, it will be necessary to replace or repair the crankshaft.
  16. Remove the flattened gauging plastic.
  17. Measure the remaining journals.

Final Crankshaft Bearing Installation Procedure

    Important: If undersized bearings are used, ensure that the bearings are fitted to the proper journals.


    Object Number: 65454  Size: SH
  1. Install the upper crankshaft bearings to the block.
  2. Install the lower crankshaft bearings to the crankshaft bearing caps.
  3. Lubricate the crankshaft bearings with clean engine oil.
  4. Install the crankshaft.
  5. Notice: In order to prevent the possibility of cylinder block or crankshaft bearing cap damage, the crankshaft bearing caps are tapped into the cylinder block cavity using a brass, lead, or a leather mallet before the attaching bolts are installed. Do not use attaching bolts to pull the crankshaft bearing caps into the seats. Failure to use this process may damage a cylinder block or a bearing cap.

  6. Install the crankshaft bearing caps and the bolts. Ensure that the arrows on the crankshaft bearings caps are facing the front of the engine. Do not install the rear crankshaft bearing cap at this time.
  7. Important: Tighten inside bearing cap bolts first and outside bearing cap bolts last.

    Tighten
    Tighten the crankshaft bearing cap bolts to 135 N·m (100 lb ft).

    Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.


    Object Number: 65851  Size: SH
  8. Apply anaerobic sealing compound to the rear bearing cap sealing face or to the rear bearing cap channel of the engine block, from the corner of the rear thrust bearing pocket to the edge of the channel.
  9. Install the rear crankshaft bearing cap and the bolts to the block.
  10. Install the rear crankshaft bearing cap bolts temporarily to 4 N·m (35 lb in).

  11. Object Number: 35199  Size: SH
  12. Measure the crankshaft end play as follows:
  13. 9.1. Firmly thrust the crankshaft first rearward then forward. This will line up the rear crankshaft bearing and the crankshaft thrust surfaces.

            Important: Tighten inside bearing cap bolts first and outside bearing cap bolts last.

    Tighten
    Tighten the rear crankshaft bearing cap bolts to 135 N·m (100 lb ft).

    9.2. With the crankshaft wedged forward, measure at the front end of the rear crankshaft bearing with a feeler gauge. The proper clearance is 0.0508 - 0.2540 mm (0.002 - 0.010 in)
  14. Inspect the crankshaft for binding as follows:
  15. 10.1. Try turning the crankshaft to check for binding.
    10.2. If the crankshaft does not turn freely, loosen the crankshaft bearing cap bolts on one cap at a time until the tight bearing is located.
    10.3. A bent crankshaft or lack of bearing clearance could cause binding.
  16. A lack of bearing clearance may be caused by the following conditions:
  17. • Burrs on the bearing cap.
    • Foreign matter between the bearing and the block.
    • Foreign matter between the bearing and the bearing cap.