Thanks everyone for all the input. I stopped the shop and took the truck for an extended trip that includes a location where the vibration was always obvious. Neither my wife nor I detected the vibration at any time in the trip including the location where it had previously been obvious. The shop had verified the vibration on a test drive and then felt they were able to duplicate it in the shop by sound with the truck running an rear stands. They replaced the U joints and balanced the drive shaft twice and then replaced the drive shaft with a different rebuilt unit and continued to hear the sound so felt they hadn't found the vibration. My test indicates that the vibration I wanted fixed was fixed with the drive shaft repairs and whatever sound they were chasing wasn't what I felt in the seat of my pants. My conclusion is that new U joints and re-balance of the drive shaft is what it needed and that fixed the vibration. In the trouble shooting I paid for some over due servicing which is OK by me and they spent significant unpaid time searching for a phantom sound attributed to the vibration I wanted fixed. I suspect the sound and my vibration are related but unloaded on stand conditions are different than real on road conditions and the latter is what is important to me. Thanks again.