I did search through the vibration after lift threads, and didn't find anything close to my particular situation. I have the rear TSB AAL done a year ago and had no vibrations from that. Just installed 5100's set at 1.75, and now the truck has a very rhythmic vibration. It will vibrate for about a second, then stop for about a second, the faster I go the faster the rhythm. Sometimes though, it doesn't do it at all, even at slow speeds.
Any ideas? My tires were just balanced, I have not gotten my new alignment yet though, because I'm going to lift the front more because 1.75 didn't level it, back is still quite a bit higher.