* Rod Knock: This is a loud, rhythmic knocking sound that gets worse with engine speed. It indicates a connecting rod bearing is failing. This is a very serious problem and requires immediate engine repair.
* Main Bearing Knock: Similar to rod knock, but the sound may be less rhythmic. This indicates a crankshaft main bearing is failing. This is also a very serious problem.
* Crankshaft Issues: A bent or damaged crankshaft can cause knocking or rumbling.
* Low Oil Pressure: Insufficient oil pressure can lead to bearing damage, resulting in the noises described. Check your oil pressure gauge immediately. Low oil level is a possible cause.
* Loose or Damaged Components: While less likely to cause a *lower-end* noise, something like a loose flywheel or flexplate *could* contribute to vibrations felt in the lower engine.
Do NOT continue driving the vehicle. Driving with a failing bearing will cause significant internal engine damage, leading to a costly or even total engine rebuild.
What you should do:
1. Check your oil level immediately. Low oil is a major cause of bearing failure.
2. Check your oil pressure. A low reading points to a serious problem.
3. Listen carefully to the noise. Try to determine if it's rhythmic (like a knock) or a more constant rumble. This information is vital for diagnosis.
4. Have a mechanic inspect the engine ASAP. A professional diagnosis is crucial to determine the extent of the damage and the necessary repairs. Ignoring the problem will only make it worse and more expensive.
The 4.3L Vortec V6 is known for potential lower-end issues, especially if maintenance (oil changes, etc.) has been neglected. Ignoring this noise could lead to complete engine failure.
