Update: I purchased this item in June 2019. In January 2020 the knocking problem started again. I did some research to see how long the warranty lasts for Ford parts and it showed 1 year for this particular part. So I emailed the seller and explained that I had a problem with the product they were selling me and that it was defective. They replied that according to Amazon's requirements, their warranty is only valid for 30 days. My advice: never buy auto parts from unauthorized sellers as they do not guarantee their parts like an authorized seller!