hey guys new to the site, havin a problem with my 03 6.0 4x4. i was on my way to vegas from arizona and after about a 2 hour drive i had this really loud vibration which felt like it was coming from right under my seat, i pulled to the side and stopped, tried again and it was gone. now it is intermittent comes and goes. took it to a driveline shop and they replaced the carrier bearing and checked the front hubs, but that didnt fix it. so i pulled the autohub out and drove it and it still happened. I cant figure this out, if it was a bearing or u joint it would do it all the time, but this vibration comes and goes. any help would be appreciated