Tools Required

Crankshaft bearings are a precision insert type. If clearances are found to be excessive, a new bearing, both upper and lower halves, will be required. Service bearings are available in standard size and undersize. Replace both bearing shells as a set.

1. Remove the oil pan. Refer to Oil Pan Replacement .
2. Remove the oil pump screen. Refer to Oil Pump Suction Pipe and Screen Assembly Replacement .



3. Remove the spark plugs.



4. Remove bearing cap side bolts.
5. Remove bearing cap bolts.
6. Remove the bearing cap using the J 41348 .
7. Remove the lower crankshaft bearing.
8. Insert the J 8080 into the oil hole in the crankshaft journal.
9. Rotate the crankshaft allowing for the J 8080 to push against the insert's straight, unnotched side. This will role the upper bearing out of the block.
10. Remove the J 8080 from the crankshaft.
11. The lower half of the crankshaft bearing insert (except the number one bearing) shows a greater wear and most distress from fatigue. If upon inspection the lower half is suitable for use it can be assumed that the upper half is also satisfactory. If the lower half shows evidence of wear or damage, both upper and lower halves should be replaced. Never replace one half without replacing the other half.

Important: 

•	In order to obtain the most accurate results when checking the crankshaft bearing clearances, use gauging plastic.

•	When the engine is in the vehicle, the crankshaft must be supported upward in order to remove any clearance from the upper bearing. The total clearance can then be measured between the lower bearing journal.

•	In order to ensure proper seating of the crankshaft, all bearing cap bolts should be at their specified torque. Clean the crankshaft journal and bearing surfaces of oil prior to checking the bearings fit.

12. With the oil pan and oil pump screen removed, and starting with the rear crankshaft bearing, remove the bearing cap using the J 41348 Main Bearing Cap Puller.

Important: Do not rotate the crankshaft while the gauging plastic is between the bearing and the journal.

13. Place a piece of gauging plastic full width or the bearing, parallel to the crankshaft, on the journal.
14. Install the bearing cap and evenly tighten the retaining bolts to specifications in order to ensure a proper reading. Variations in torque affect the compression of the gauging plastic.

Important: Begin to tighten the bearing cap bolts by hand. Tighten all of the bearing caps in equal increments. Do not tighten one cap completely at a time.

15. Use the following procedure to tighten the fasteners:

Tighten

1. Tighten the bearing cap bolts to 70 N·m (52 lb ft) to fully seat the caps.
2. Loosen the bearing cap bolts 360 degrees CCW.
3. Tighten the crankshaft bearing cap bolts to 20 N·m (15 lb ft), then to 40 N·m (30 lb ft), then use the J 36660-A in order to rotate the bolts in order 35 degrees + 35degrees + 40degrees, for a total of 110 degrees.
4. Tighten the crankshaft bearing cap sid bolts to 15 N·m (11 lb ft). Use the J 36660-A in order to rotate the bolts an additional 45degrees.
16. Remove the bearing caps.
17. Without removing the gauging plastic, measure its compressed width (at the lowest point) with graduations on the gauging plastic envelope. 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 journal 0.005 mm (0.0002 in) maximum, ensure to fit the bearing to the maximum diameter of the journal. If the bearing is fitted to a minimum diameter, and the journal is out-of-round 0.005 mm (0.0002 in) or more, interference between the bearing and the journal will result in rapid bearing failure. If flattened gauging plastic tapers toward the middle or ends, there is a difference in clearance indicating taper, low spot or other irregularity of the bearing journal. Ensure to measure the journal with a micrometer if the flattened gauging plastic indicates this difference.
18. If the bearing clearance is within specifications, the bearing insert is satisfactory. If the clearance is not within specifications, replace the insert. Always replace both the upper and lower inserts as a unit. When the bearing cap is installed and the clearance is less than 0.032 mm (0.0012 in), inspect it for burrs or nicks.
19. An undersize bearing may produce proper clearance. If not, it will be necessary to regrind the crankshaft journal for use with the next undersize bearing. After selecting the new bearin, recheck the clearance.
20. Proceed to the next bearing. When checking the number one crankshaft bearing, remove the drive belt in order to prevent tapered reading with gauging plastic. After all bearings have been checked, rotate the crankshaft in order to check that there is no excessive drag.

1. Install the crankshaft bearings into the engine block and into the bearing caps. Use the following procedure:

1.1.	Coat the crankshaft bearings with oil.

1.2.	Insert the plain, unnotched end between the crankshaft and the indented or notched side of the block. Rotate the bearing into place. Use the J 8080. Remove the J 8080 from the hole in the crankshaft journal.

Notice: The #4 (rear) main bearing cap must be installed flush with the torque converter bolt heads or 0.25 mm (0.010 in.) forward of the rear face of the cylinder block to avoid interference with the flywheel.

2. Use sealer GM P/N 1052942 or equivalent at the number four bearing cap to the engine block surface.
3. Install the crankshaft bearing caps with the assembled crankshaft bearings inside and with the arrows pointing to the front of the engine.



4. Install the crankshaft bearing cap bolts. With the crankshaft, crankshaft bearings and bearing caps installed and the bolts started, thrust the crankshaft rearward in order to set and align the bearing caps. Then force the crankshaft forward to align the crankshaft thrust bearing.

Tighten

•	Tighten the crankshaft bearing cap bolts to 40 N·m (30 lb ft). Use the J 36660-A in order to rotate the bolts an additional 35 degrees + 35 degress + 40degrees for a total of 110 degrees.

•	Tighten the crankshaft bearing cap side bolts to 15 N·m (11 lb ft). Use the J 36660-A in order to rotate the bolt an additional 45 degrees.




5. Measure the crankshaft end play. Use a dial indicator or a feeler gauge. If you are using a feeler gauge, measure between the front of the bearing cap and the crankshaft thrust surface.
6. Install the oil pump screen. Refer to Oil Pump Suction Pipe and Screen Assembly Replacement .
7. Install the oil pan. Refer to Oil Pan Replacement .
8. Install the spark plugs.