1993 Toyota Pickup don't know what to do

Recently my truck started riding rough and felt like something in the rear is rubbing or something is clogged. When I take off the whole truck vibrates a lot. I changed the spark plugs, plug wires, pcv valve, added oil, coolant, fuel injector cleaner, rear end oil and aired the tires some. I think there is a small leak in one of the rear seals but it rode fine. My truck feels sick!