I bought a 2001 Ram1500 3.9L from the USDA & only 42K miles. There is noise (sounds like valve train noise). This is was USDA truck used on a farm in a VERY VERY dirty environment. I have seen several blogs that say timing train valve noise is normal. Some blogs say the OEM timing chains in early-mid 90s timing chains are weak. Usually factory problems last only a year or two. What is the deal here with this noise in a 2001 3.9 only 42K confirmed miles?