Shimmy above 70 MPH

[nmu98]

Pulling to the right can be a caster or even camber issue. When you run light on caster it will happen or if your camber is not the same, or within a small degree off...

Your vibration is most likely not from the alignment. It is most likely a tire out of balance or your u joints in your rear driveshaft. How much lift do you have? What size tires?

On edit, the title says shimmy, but the post says vibration.... Please clarify.