I have a 06 LBZ 2WD that developed a vibration when taking off @ about 10-15mph & then it would vibrate again when coming to a stop. I needed new tires so I went ahead & had a new set installed although I knew the tires were not the issue. Thinking it might be a U-joint I took it down to our Amco shop & they said it did have a tight u-joint in the rear. Being the truck has 200K on it I had them replace all the U-joints & the Carrier bearing. This stop the vibration issue when taking off & stopping. But now I have a vibration between 35-40 Mph. I can run the truck up to 50 Mph & put it in neutral & let it fall back under 40 & still get the vibration. I took it back and they double checked everything & even rotated the drive shaft 90 deg. Still no luck. I then took it to a drive train shop to check for Balance. Shaft was with in spec but they went ahead and improved the balance & re-checked all the U-joints but this did not solve the problem. The drive train shop says it may be the Torque convertor causing it. I tend to disagree as It does it in neutral while coasting & also you can drop it in a lower gear & it still does it between 35-40Mph. I am at a loss now on what to do.