A slight knocking or thud sound may be heard coming from the steering column area when driving some 2014-2025 Silverado 2500HD/3500HD and Sierra 2500HD/3500HD trucks over rough roads or potholes. In some cases, the knocking condition also may be felt in the steering wheel. The condition may be more noticeable when turning and driving over a bump or uneven surface. (Fig. 12)
Fig. 12
The knocking or thud sound may be a normal condition with the hydraulic steering system known as hydraulic hammer. It is caused by irregular road surfaces feeding back into the steering gear through the tires and steering linkage. The sound and steering wheel feedback can be more pronounced with larger wheels and tires. (Fig. 13)
Fig. 13
To determine if a hydraulic hammer condition is present, test drive the vehicle over rough road surfaces while listening for a knocking or clunking sound. Also check for any feedback in the steering wheel. Next, perform the same steering maneuvers while driving on smooth pavement.
The sound also may be caused by steering through a pavement transition with a height difference, such as turning out of a concrete driveway down onto a gravel road or turning from a paved road into a parking lot.
If the sound is present only on the rough road surfaces or pavement transitions, it is likely to be the hydraulic hammer condition enabled by the road surface.
Be sure to compare the condition with another HD truck with a similar tire and wheel combination and steering system (RPO NV8 or non-NV8). If the condition is comparable to another truck, no parts should be replaced for this condition. Inform the customer of the operating characteristics of the steering system.
For more information, refer to Bulletin #24-NA-185.
Thanks to Kevin Minor
