Ford Repair: Vibration, aluminum shaft, drive shaft

Question
Hi James,
I have a 2002 SuperCab F150.4.6l Auto Trans. 2WD. Stock no add-ons. It has about 90,000 miles. I have been having a problem with a vibration that is felt in the seat of the truck. I have had this vibration for 2 years. Thought it was bad shocks and changed all to Bilsteins. Replaced the rear brake rotors. Released the parking brake until I can find the problem. I have purchased new tires. I have the same symptoms. The rear vibrates at about 40 mph and worse if at high speeds on the interstate. I have had the driveshaft balanced. The drive shaft is the long single aluminum shaft. I even bought a used shaft and replaced the u-joints and the same symptoms. Last week I took the truck to a Transmission shop that works on drivelines. He felt that the vibration was suspension related. Not the driveline.I know that the 2004 had a problem with suspension vibration and the frame dampner was installed. Do you know of any reason for this vibration? Any TSB? The tires wear even. If I rotate the tires front to back the vibration is  the same. I'm not sure where to go next?

Answer
The following is TSB Recall numbers and description./ (02-21-11 OCT 02    Body - Cab Oscillation/Bounce at Highway Speeds). Contact your local dealer for instructions. This seems applicablew to your truck given the description that you cited. When calling the dealership, give them the following numbers.(02-21-11 OCT 02). You will need the damper assembly installed.