I also noticed a thumping sound when I went over humps. Thats when i looked at the bottom and found hydraulic oil all over my LCA. I thought at first that it was a seal until i took the shock out. I dropped off the shock to Aldan American two days ago and told them that the top cover spins out. They will also service my other shock as well. I think the vibration affects the shock when you drive fast on dirt roads. I will give an update when i talk to the techs at Aldan American.