Need 6.0 help

[brandglend]

I have a 2004 6.0 F250 and about two weeks ago it started to kind of growl at me at low speeds about 20-30 MPH. It happens when your foot is on the gas just enough to keep at a constant speed. There is also a slight vibration in the pedal when this happens. The truck started this all of sudden and I have had it at a transmission shop and they say the transmission is fine. Im not sure if the computer has ever been updated. I have owned the truck for 2 years and I have never hat it updated so I will take it Tuesday for all its updates and I hope this fixes it. I have heard it should. Does anyone have any info