If it is sitting lower in the rear on the drivers side, it is a rear spring issue. They wear out, and sag on that side, most of the weight is over there. You can make up some of it with a TT (torsion twist) but the only way to completely get rid of it is to do some spring work back there.
If you haven't replaced any of the front end components, i.e. ball joints, tie rod ends, control arm bushings, you will get that shake. You can jack up the car, and shake the wheel 3-9 or 12-6, you have loose parts, and need to replace them. If you look at the front of the truck and it looks like this: /-----\ you probably have worn out parts too.