Knocking noise is more significant at times and other times hardly noticeable. Took it back once under recall. Same thing started back up a year or so later. I think that is sad when you recall something but still can't fix it right. I really like my truck but Chevrolet as a company is pathetic. Obama Government Motors should have went under. I am not willing to buy anything else from them. Quality control is not a priority with Govt Motors corporation. 2002 Silverado 5.3L LS ext cab 55k original miles