Drive line noise mystery? Solved

[alborz]

Here is the story
I called peterbilt dealership to make an appointment for a three axle alignment. They said they don’t do it at their shop and send their customers to another shop nearby. Ok took the address and drove there. They said your bushings are bad and need to be replaced before aligning axles. “Ok do it” I said. After few days They informed that my truck is ready. Ok I picked the truck and on way home I heard a strange noise from under the cab. I pulled over checked everything and backed to the shop. He looked and said we’ve done our job and that noise is not from our job.
I did some research and did the following.
Replaced air ride level valve. And
Checked/ rechecked height level over ond over and over
Rebuilt transmission because I thought that might be from bad tranny
Cut and balanced new drive shaft
Changed u- joints and carrier bearing
Dropped and Checked both differentials and their components
Put new driver tires

And still the noise is there. At 55 mph when bobtail or from 60 plus mph when hooked to trailer and truck simply coast or downhill. If I push the clutch or put the gear in neutral or when accelerating [/b]the noise goes away. Other than that it is on my nerve.