Connecting Rod Noise

A damaged or worn connecting rod bearing will produce knock under all speeds. During the early stages of wear, connecting rod noise may be confused with piston slap or loose wrist pins. Connecting rod knock noise increases in volume with engine speed and is at its loudest on deceleration. Causes of connecting rod bearing noise include:
- Excessive bearing clearance
- Worn crankshaft connecting rod journal
- Thin, diluted or dirty oil and/or filter
- Low oil pressure
- Crankshaft connecting rod journals out-of-round
- Misaligned connecting rod
- Connecting rod bolts not properly torqued
- Wrong bearing inserts or misaligned bearing half