vibration in gas pedal

[mcioci]

Now dealer says they dont know what the noise is. They are not sure its the front diff. They were saying it might be coming from my roof cage or front brush grille. I said how could that be? The noise is from 45-65mph and on acceleration. I said since the vibration is in pedal and noise is definitely coming from under the car it cant be the roof cage or brush guard.

I did wire brush the rust on bottom of truck and spray rustoleum. Could that have caused this groaning sound from 45-65mph? it did start happening right after this.