I have a 2004 Ford F150 4X4 (new Style). For some time I have had a vibration in the drive train when starting out on a hill or when pulling a trailer. It only occurs for a short period of time and then goes away as speed increases. I have checked the universal joints and they are fine.
Posi-trac acting up ?
Has this 4X4 been lifted? If so the nose angles of the differentials may have to adjusted.
Auto or Manual? I suspect Auto (such a tragedy 
)