The engine on my 22 Sierra began knocking at 23,000 miles . The engine i have is a 6.2. It was already scheduled for a front grill recall at the dealer and I had concerns for the knocking issues. I had no lights on the dash or a performance issue at the time. The dealer said they heard the knocking and wanted to take the oil filter off to confirm engine failure. The found metal shavings in the filter and it needed a new engine. They said if I kept driving it the engine would have locked up . Luckily I cought it in time and avoided an accident on the highway. This is a huge safety issue.