Well i just bought my very first diesel which is a '05 F250 CC King Ranch with about 31,500 miles on it. It drives great and looks even better. I do have one concern and a question for you experts out there. When I am driving up the mountain pass here in my area and hit between 45 and 50 MPH I get this constant vibration in the truck which is about the same type of vibration as say that of a cell phone when it rings on vibrate mode. But of course this is constant and once I accelerate a little more or let off the gas it stops. Doesn't do it at other speeds. No change in the RPM's either. I have 18" Goodyear Wrangler tires on the truck now and it is bone stock with 3.73 gears. Thanks for any help.