Check out my rear end

[AuroraGirl]

Another thing to look into for a small vibration (especially if it comes and goes) is wheel runout and tire balance. That's something that I have fought with my '85 ever since I put the 20s on. Sometimes the vibration will be enough the whole truck shakes (mildly, but still) and then I go around a corner and it's gone. It's something in my rear wheel/tire balance and phasing. I need to have the tires pulled off and the wheels spun up by themselves to see how bad they are since they're just cheap cast wheels. I guarantee that's my problem. Also road force balancing is a godsend if you can find a shop that'll do it

also.
Brake rotor can do the same thing