Have an 02 Duramax and have a problem with adequate oil getting to the rocker assembly. First failure was a broken rocker shaft, parts replaced and valves adjusted. Second failure was valve adjustment not holding proper clearance, readjusted valves, Third failure was valve adjustment again. Analysis indicates that improper amount of oil getting to valve train on right side. Engine has only 47k mileage and has only about 12k of that being used to tow a 5th wheel and stopped doing that about 3 years ago. This has all occurred in the past 5k miles or so. If anyone has seen this problem or has any idea as to what the root cause could be I would greatly appreciate feedback.