I have an 2004 with the 4.0 and manual transmission. The engine has developed a slight vibration that gets worse as the rpm gets higher. Nothing alarming but you can defiantly feel it. I just wanted to see if anyone could give me ideas on what to start with. Motor mounts are original and look good but I will probably change them. It has new plugs and is not throwing any codes. It still vibrates even with the belt off. Probably unrelated but I am getting a noise (slight squeal) from what seems like the clutch area that goes away when I put pressure on the clutch.