Chevrolet Silverado / GMC Sierra. Service manual — part 144

1. Firmly thrust the crankshaft first rearward, then forward. This will align the crankshaft

rear bearings and the crankshaft thrust surfaces.

2. With the crankshaft pushed forward, insert a feeler gage between the crankshaft and

the crankshaft bearing surface and then measure the clearance. The proper crankshaft
end play clearance specification is 0.050-0.20 mm (0.002-0.008 in).

3. Turn the crankshaft to check for binding. If the crankshaft does not turn freely, then

loosen the crankshaft bearing cap bolts, one crankshaft bearing cap at a time, until the
tight crankshaft bearing is located.

Burrs on the crankshaft bearing cap or engine block, foreign matter between the
crankshaft bearing and the crankshaft bearing cap or the engine block, or a faulty
crankshaft bearing could cause a lack of clearance between the crankshaft and
crankshaft bearing.

IMPORTANT: In order to properly measure the crankshaft end play, the

crankshaft, the crankshaft bearings, the crankshaft
bearing caps, and the crankshaft bearing cap bolts must
be installed into the engine block and the bolts tightened
using J 45059 . See Special Tools. The proper crankshaft
bearing cap bolt tightening specification first pass is 20
N.m (15 lb ft), final pass is 73 degrees.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

Fig. 483: Identifying Crankshaft Bearing Craters Or Pockets
Courtesy of GENERAL MOTORS CORP.

11. Inspect the crankshaft bearings for craters or pockets. Flattened sections on the crankshaft

bearing halves also indicate fatigue.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

Fig. 484: Identifying Connecting Rod Bearing Scoring Or Discoloration
Courtesy of GENERAL MOTORS CORP.

12. Inspect the crankshaft bearings for excessive scoring or discoloration.

13. Inspect the crankshaft bearings for dirt or debris imbedded into the crankshaft bearing

material.

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado

Fig. 485: Crankshaft Bearing Polished Sections (Improper Seating)
Courtesy of GENERAL MOTORS CORP.

14. Inspect the crankshaft bearings for improper seating indicated by bright, polished sections of

the crankshaft bearings.

If the lower half of the crankshaft bearing is worn or damaged, both the upper and
lower halves of the crankshaft bearing should be replaced.

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

Measuring Crankshaft Bearing Clearances

2008 Chevrolet Silverado 1500

2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado