Rattle Noise From Bottom Rear Of Engine At 2000-3000 RPM - keywords accelerate acceleration balance bell bellhousing buzz clatter detonation end hot housing idle knock load lower off ping shaft spark

This PI was superseded to update Recommendation/Instructions. Please discard PIP3811.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

On rare occasions, a light detonation/rattle type of noise may be experienced around 2,000 - 3,000 RPM under light load/acceleration with the engine at operating temperature. This noise may be the result of balance shaft movement and does not present any adverse effect to the engine or any of its components. This noise is generally the loudest at the lower rear of the engine (bell housing area) when listening from under the vehicle.

In some instances, detonation noise could be mistaken for this balance shaft noise. If detonation noise is present due to poor fuel quality, lean fueling, or high engine temperature, follow the "Detonation/Spark Knock" Diagnostics in SI and repair the cause of detonation as necessary.

If detonation is not the source of this noise and the SI diagnostics do not reveal another cause for this noise, compare the noise to a known good vehicle that is the same model year and equipped with the same engine. If the same noise is present in both vehicles, this should be considered a noise characteristic of the balance shaft system. If the noise is excessive when compared to a known good vehicle, contact GM Technical Assistance to set up a TAC case and receive additional suggestions from the Internal Administrative Details Section of this PI.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.