The knocking sound generated from a bad GMC Connecting Rod Bearing is unmistakable. This is a deep constant sound emanating from the lower section of the engine block when the motor is operating. The most common cause for one or more connecting rod bearings to fail in your GMC engine is because of infrequent oil changes which have left the bearing scared. In extreme conditions, the dirty oil has clogged the oil galley in the bearing causes this moving part to be void of any lubricant.
If your GMC motor is making this deep knocking sound, it is only a matter of time before the damage is so severe that not only will the connecting rod bearings have to be replaced, but also the crankshaft if this condition is not addressed. When the engine is taken apart and the connecting rod bearings removed, the condition of the crankshaft can then be inspected and a determination made on if there is any damage to it.
The replacement of the GMC connecting rod bearings requires not only that the connecting rod be measured where the bearing is being fitted into it, but also the crankshaft. This way the correct amount of clearance for the new connecting rod bearing can be determined and installed. This set of measurements can only be properly done with am micrometer. This is a measuring device that records differences in thickness to a thousandth of an inch.
With a new one or set of connecting rod bearings in the GMC engine its lifespan has just been increased. To help ensure their longevity, regular oil changes should occur once this repair procedure is accomplished or it will have to be repeated in the future.