Ping Pop Or Click Noise From Under The Rear - keywords accelerate axle differential drive driveline garage gear intermittent launch load noise park ping pop prop propeller propshaft rear reverse whin

This PI was superseded to update Condition/Concerns. Please discard PIP3420C.

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

Some customers with the models listed may comment on a ping, pop or click noise from underneath the rear of the vehicle. This concern usually occurs when shifting into reverse or out of reverse into drive or also on launch. Some vehicle may duplicate this concern without moving the vehicle and others may require the vehicle to actually move in one direction or the other with moderate acceleration (forward or reverse). The customer may also identify the noise while slowing to a stop while the transmission is down-shifting and/or during moderate to heavy braking).

Note: This PI also applies to Chevrolet SSR equipped with an automatic transmission and a whine noise or a manual or automatic with the click ping type noise.

There are two different areas that could cause these very similar symptoms. Some are caused by the propeller shaft internally and some may have an issue within the rear axle assembly. Diagnosis for this concern should be as follows:

Since the propshaft is easier to diagnose, it should be addressed first but only if the vehicle is equipped with an aluminum propshaft. Steel propshafts generally do not exhibit this concern. The best way to diagnose is to swap a "quiet" propshaft from a known good vehicle. If the noise is now in the known good vehicle, the propshaft is the cause of the noise. If a donor vehicle is not available, experience has shown that installation of a replacement aluminum propshaft typically repairs the noise for a period of time. If installing a new propshaft does not improve the noise, most likely the propshaft is NOT the root cause of the concern. Most "noisy" propshafts are able to be duplicated by simply shifting between drive and reverse without actually moving the vehicle.

If swapping the propshaft does not improve the concern and/or the vehicle MUST move, launch, be driven with moderate acceleration or during deceleration to duplicate the noise, the noise may be coming from the rear axle housing itself. Replacement of the rear axle housing will be required to repair this condition.

On Trailblazer EXT 2WDs and Envoy XL 2WDs equipped with a 3.42 axle ratio (RPO GU6), or a 3.73 axle ratio (RPO GT4), this condition may be corrected by replacing the original swaged aluminum propshaft with a straight tube propshaft from the GMC Envoy XUV.

On Trailblazer EXT 2WD and Envoy XL 2WD with the 3.42 GU6 or 3.73 GT4 ratio, the part numbers for the replacement propshaft are:

The propshafts mentioned above can NOT be used in Trailblazer EXT 2WDs and Envoy XL 2WDs with the 4.10 axle ratio (RPO GT5). If this concern appears on a vehicle with the 4.10 ratio, use P/N 15163667, which is the same as the original propshaft.

On Chevrolet SSRs, revised propshaft for automatic transmission vehicles P/N 15247556 was released for service which includes an integral mass damper, mounted on the 'slip-yoke' (transmission end) to improve a driveline whine concern. Manual transmission (6-speed) vehicles will use P/N 15209860 which has a larger rear u-joint to fit the 9.5" rear axle. These propshafts have also been changed internally to reduce the "ping" "creak" or "click" noise when you change direction of the propshaft.

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.