There is a noise in drivetrain a virbration. - 1996 Dodge Caravan

This could very well be one of several common things. The first could be a wheel that needs to be balanced at a tire shop, if the vibration starts after a certain speed this is the most likely cause. Another possibility is if the belt(s) in the tire have separated, if the vehicle moves from side to side slightly like a dog shakes its hind quarters then you should get the tires checked right away. Third possibility is warping/glazing of the brake rotor(s) caused by overheating from heavy repeated braking or a hard stop or not being replaced at a previous pad replacement. Fourth possibility is that one of the wheels is coming loose and this happens if the lug nuts are not tightened down properly during service work, you can tell this by pulling off your hub caps and looking at the center of each wheel and checking to see if the center of the wheel is flat against the hub or you can get the jack out and raise each corner one at a time and check for a loose wheel. Fifth problem could be a bad suspension part such as a bad wheel bearing which will cause a howling noise, a ball joint which can cause a popping noise as would a bad tie rod end. If you are mechanically inclined enough most of these you can diagnose easily yourself with the right tools and patience.